Background: #fff
Foreground: #000
PrimaryPale: #8cf
PrimaryLight: #18f
PrimaryMid: #04b
PrimaryDark: #014
SecondaryPale: #ffc
SecondaryLight: #fe8
SecondaryMid: #db4
SecondaryDark: #841
TertiaryPale: #eee
TertiaryLight: #ccc
TertiaryMid: #999
TertiaryDark: #666
Error: #f88
/*{{{*/
body {background:[[ColorPalette::Background]]; color:[[ColorPalette::Foreground]];}

a {color:[[ColorPalette::PrimaryMid]];}
a:hover {background-color:[[ColorPalette::PrimaryMid]]; color:[[ColorPalette::Background]];}
a img {border:0;}

h1,h2,h3,h4,h5,h6 {color:[[ColorPalette::SecondaryDark]]; background:transparent;}
h1 {border-bottom:2px solid [[ColorPalette::TertiaryLight]];}
h2,h3 {border-bottom:1px solid [[ColorPalette::TertiaryLight]];}

.button {color:[[ColorPalette::PrimaryDark]]; border:1px solid [[ColorPalette::Background]];}
.button:hover {color:[[ColorPalette::PrimaryDark]]; background:[[ColorPalette::SecondaryLight]]; border-color:[[ColorPalette::SecondaryMid]];}
.button:active {color:[[ColorPalette::Background]]; background:[[ColorPalette::SecondaryMid]]; border:1px solid [[ColorPalette::SecondaryDark]];}

.header {background:[[ColorPalette::PrimaryMid]];}
.headerShadow {color:[[ColorPalette::Foreground]];}
.headerShadow a {font-weight:normal; color:[[ColorPalette::Foreground]];}
.headerForeground {color:[[ColorPalette::Background]];}
.headerForeground a {font-weight:normal; color:[[ColorPalette::PrimaryPale]];}

.tabSelected{color:[[ColorPalette::PrimaryDark]];
	background:[[ColorPalette::TertiaryPale]];
	border-left:1px solid [[ColorPalette::TertiaryLight]];
	border-top:1px solid [[ColorPalette::TertiaryLight]];
	border-right:1px solid [[ColorPalette::TertiaryLight]];
}
.tabUnselected {color:[[ColorPalette::Background]]; background:[[ColorPalette::TertiaryMid]];}
.tabContents {color:[[ColorPalette::PrimaryDark]]; background:[[ColorPalette::TertiaryPale]]; border:1px solid [[ColorPalette::TertiaryLight]];}
.tabContents .button {border:0;}

#sidebar {}
#sidebarOptions input {border:1px solid [[ColorPalette::PrimaryMid]];}
#sidebarOptions .sliderPanel {background:[[ColorPalette::PrimaryPale]];}
#sidebarOptions .sliderPanel a {border:none;color:[[ColorPalette::PrimaryMid]];}
#sidebarOptions .sliderPanel a:hover {color:[[ColorPalette::Background]]; background:[[ColorPalette::PrimaryMid]];}
#sidebarOptions .sliderPanel a:active {color:[[ColorPalette::PrimaryMid]]; background:[[ColorPalette::Background]];}

.wizard {background:[[ColorPalette::PrimaryPale]]; border:1px solid [[ColorPalette::PrimaryMid]];}
.wizard h1 {color:[[ColorPalette::PrimaryDark]]; border:none;}
.wizard h2 {color:[[ColorPalette::Foreground]]; border:none;}
.wizardStep {background:[[ColorPalette::Background]]; color:[[ColorPalette::Foreground]];
	border:1px solid [[ColorPalette::PrimaryMid]];}
.wizardStep.wizardStepDone {background:[[ColorPalette::TertiaryLight]];}
.wizardFooter {background:[[ColorPalette::PrimaryPale]];}
.wizardFooter .status {background:[[ColorPalette::PrimaryDark]]; color:[[ColorPalette::Background]];}
.wizard .button {color:[[ColorPalette::Foreground]]; background:[[ColorPalette::SecondaryLight]]; border: 1px solid;
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.wizard .button:hover {color:[[ColorPalette::Foreground]]; background:[[ColorPalette::Background]];}
.wizard .button:active {color:[[ColorPalette::Background]]; background:[[ColorPalette::Foreground]]; border: 1px solid;
	border-color:[[ColorPalette::PrimaryDark]] [[ColorPalette::PrimaryPale]] [[ColorPalette::PrimaryPale]] [[ColorPalette::PrimaryDark]];}

#messageArea {border:1px solid [[ColorPalette::SecondaryMid]]; background:[[ColorPalette::SecondaryLight]]; color:[[ColorPalette::Foreground]];}
#messageArea .button {color:[[ColorPalette::PrimaryMid]]; background:[[ColorPalette::SecondaryPale]]; border:none;}

.popupTiddler {background:[[ColorPalette::TertiaryPale]]; border:2px solid [[ColorPalette::TertiaryMid]];}

.popup {background:[[ColorPalette::TertiaryPale]]; color:[[ColorPalette::TertiaryDark]]; border-left:1px solid [[ColorPalette::TertiaryMid]]; border-top:1px solid [[ColorPalette::TertiaryMid]]; border-right:2px solid [[ColorPalette::TertiaryDark]]; border-bottom:2px solid [[ColorPalette::TertiaryDark]];}
.popup hr {color:[[ColorPalette::PrimaryDark]]; background:[[ColorPalette::PrimaryDark]]; border-bottom:1px;}
.popup li.disabled {color:[[ColorPalette::TertiaryMid]];}
.popup li a, .popup li a:visited {color:[[ColorPalette::Foreground]]; border: none;}
.popup li a:hover {background:[[ColorPalette::SecondaryLight]]; color:[[ColorPalette::Foreground]]; border: none;}
.popup li a:active {background:[[ColorPalette::SecondaryPale]]; color:[[ColorPalette::Foreground]]; border: none;}
.popupHighlight {background:[[ColorPalette::Background]]; color:[[ColorPalette::Foreground]];}
.listBreak div {border-bottom:1px solid [[ColorPalette::TertiaryDark]];}

.tiddler .defaultCommand {font-weight:bold;}

.shadow .title {color:[[ColorPalette::TertiaryDark]];}

.title {color:[[ColorPalette::SecondaryDark]];}
.subtitle {color:[[ColorPalette::TertiaryDark]];}

.toolbar {color:[[ColorPalette::PrimaryMid]];}
.toolbar a {color:[[ColorPalette::TertiaryLight]];}
.selected .toolbar a {color:[[ColorPalette::TertiaryMid]];}
.selected .toolbar a:hover {color:[[ColorPalette::Foreground]];}

.tagging, .tagged {border:1px solid [[ColorPalette::TertiaryPale]]; background-color:[[ColorPalette::TertiaryPale]];}
.selected .tagging, .selected .tagged {background-color:[[ColorPalette::TertiaryLight]]; border:1px solid [[ColorPalette::TertiaryMid]];}
.tagging .listTitle, .tagged .listTitle {color:[[ColorPalette::PrimaryDark]];}
.tagging .button, .tagged .button {border:none;}

.footer {color:[[ColorPalette::TertiaryLight]];}
.selected .footer {color:[[ColorPalette::TertiaryMid]];}

.sparkline {background:[[ColorPalette::PrimaryPale]]; border:0;}
.sparktick {background:[[ColorPalette::PrimaryDark]];}

.error, .errorButton {color:[[ColorPalette::Foreground]]; background:[[ColorPalette::Error]];}
.warning {color:[[ColorPalette::Foreground]]; background:[[ColorPalette::SecondaryPale]];}
.lowlight {background:[[ColorPalette::TertiaryLight]];}

.zoomer {background:none; color:[[ColorPalette::TertiaryMid]]; border:3px solid [[ColorPalette::TertiaryMid]];}

.imageLink, #displayArea .imageLink {background:transparent;}

.annotation {background:[[ColorPalette::SecondaryLight]]; color:[[ColorPalette::Foreground]]; border:2px solid [[ColorPalette::SecondaryMid]];}

.viewer .listTitle {list-style-type:none; margin-left:-2em;}
.viewer .button {border:1px solid [[ColorPalette::SecondaryMid]];}
.viewer blockquote {border-left:3px solid [[ColorPalette::TertiaryDark]];}

.viewer table, table.twtable {border:2px solid [[ColorPalette::TertiaryDark]];}
.viewer th, .viewer thead td, .twtable th, .twtable thead td {background:[[ColorPalette::SecondaryMid]]; border:1px solid [[ColorPalette::TertiaryDark]]; color:[[ColorPalette::Background]];}
.viewer td, .viewer tr, .twtable td, .twtable tr {border:1px solid [[ColorPalette::TertiaryDark]];}

.viewer pre {border:1px solid [[ColorPalette::SecondaryLight]]; background:[[ColorPalette::SecondaryPale]];}
.viewer code {color:[[ColorPalette::SecondaryDark]];}
.viewer hr {border:0; border-top:dashed 1px [[ColorPalette::TertiaryDark]]; color:[[ColorPalette::TertiaryDark]];}

.highlight, .marked {background:[[ColorPalette::SecondaryLight]];}

.editor input {border:1px solid [[ColorPalette::PrimaryMid]];}
.editor textarea {border:1px solid [[ColorPalette::PrimaryMid]]; width:100%;}
.editorFooter {color:[[ColorPalette::TertiaryMid]];}

#backstageArea {background:[[ColorPalette::Foreground]]; color:[[ColorPalette::TertiaryMid]];}
#backstageArea a {background:[[ColorPalette::Foreground]]; color:[[ColorPalette::Background]]; border:none;}
#backstageArea a:hover {background:[[ColorPalette::SecondaryLight]]; color:[[ColorPalette::Foreground]]; }
#backstageArea a.backstageSelTab {background:[[ColorPalette::Background]]; color:[[ColorPalette::Foreground]];}
#backstageButton a {background:none; color:[[ColorPalette::Background]]; border:none;}
#backstageButton a:hover {background:[[ColorPalette::Foreground]]; color:[[ColorPalette::Background]]; border:none;}
#backstagePanel {background:[[ColorPalette::Background]]; border-color: [[ColorPalette::Background]] [[ColorPalette::TertiaryDark]] [[ColorPalette::TertiaryDark]] [[ColorPalette::TertiaryDark]];}
.backstagePanelFooter .button {border:none; color:[[ColorPalette::Background]];}
.backstagePanelFooter .button:hover {color:[[ColorPalette::Foreground]];}
#backstageCloak {background:[[ColorPalette::Foreground]]; opacity:0.6; filter:'alpha(opacity:60)';}
/*}}}*/
/*{{{*/
* html .tiddler {height:1%;}

body {font-size:.75em; font-family:arial,helvetica; margin:0; padding:0;}

h1,h2,h3,h4,h5,h6 {font-weight:bold; text-decoration:none;}
h1,h2,h3 {padding-bottom:1px; margin-top:1.2em;margin-bottom:0.3em;}
h4,h5,h6 {margin-top:1em;}
h1 {font-size:1.35em;}
h2 {font-size:1.25em;}
h3 {font-size:1.1em;}
h4 {font-size:1em;}
h5 {font-size:.9em;}

hr {height:1px;}

a {text-decoration:none;}

dt {font-weight:bold;}

ol {list-style-type:decimal;}
ol ol {list-style-type:lower-alpha;}
ol ol ol {list-style-type:lower-roman;}
ol ol ol ol {list-style-type:decimal;}
ol ol ol ol ol {list-style-type:lower-alpha;}
ol ol ol ol ol ol {list-style-type:lower-roman;}
ol ol ol ol ol ol ol {list-style-type:decimal;}

.txtOptionInput {width:11em;}

#contentWrapper .chkOptionInput {border:0;}

.externalLink {text-decoration:underline;}

.indent {margin-left:3em;}
.outdent {margin-left:3em; text-indent:-3em;}
code.escaped {white-space:nowrap;}

.tiddlyLinkExisting {font-weight:bold;}
.tiddlyLinkNonExisting {font-style:italic;}

/* the 'a' is required for IE, otherwise it renders the whole tiddler in bold */
a.tiddlyLinkNonExisting.shadow {font-weight:bold;}

#mainMenu .tiddlyLinkExisting,
	#mainMenu .tiddlyLinkNonExisting,
	#sidebarTabs .tiddlyLinkNonExisting {font-weight:normal; font-style:normal;}
#sidebarTabs .tiddlyLinkExisting {font-weight:bold; font-style:normal;}

.header {position:relative;}
.header a:hover {background:transparent;}
.headerShadow {position:relative; padding:4.5em 0em 1em 1em; left:-1px; top:-1px;}
.headerForeground {position:absolute; padding:4.5em 0em 1em 1em; left:0px; top:0px;}

.siteTitle {font-size:3em;}
.siteSubtitle {font-size:1.2em;}

#mainMenu {position:absolute; left:0; width:10em; text-align:right; line-height:1.6em; padding:1.5em 0.5em 0.5em 0.5em; font-size:1.1em;}

#sidebar {position:absolute; right:3px; width:16em; font-size:.9em;}
#sidebarOptions {padding-top:0.3em;}
#sidebarOptions a {margin:0em 0.2em; padding:0.2em 0.3em; display:block;}
#sidebarOptions input {margin:0.4em 0.5em;}
#sidebarOptions .sliderPanel {margin-left:1em; padding:0.5em; font-size:.85em;}
#sidebarOptions .sliderPanel a {font-weight:bold; display:inline; padding:0;}
#sidebarOptions .sliderPanel input {margin:0 0 .3em 0;}
#sidebarTabs .tabContents {width:15em; overflow:hidden;}

.wizard {padding:0.1em 1em 0em 2em;}
.wizard h1 {font-size:2em; font-weight:bold; background:none; padding:0em 0em 0em 0em; margin:0.4em 0em 0.2em 0em;}
.wizard h2 {font-size:1.2em; font-weight:bold; background:none; padding:0em 0em 0em 0em; margin:0.4em 0em 0.2em 0em;}
.wizardStep {padding:1em 1em 1em 1em;}
.wizard .button {margin:0.5em 0em 0em 0em; font-size:1.2em;}
.wizardFooter {padding:0.8em 0.4em 0.8em 0em;}
.wizardFooter .status {padding:0em 0.4em 0em 0.4em; margin-left:1em;}
.wizard .button {padding:0.1em 0.2em 0.1em 0.2em;}

#messageArea {position:fixed; top:2em; right:0em; margin:0.5em; padding:0.5em; z-index:2000; _position:absolute;}
.messageToolbar {display:block; text-align:right; padding:0.2em 0.2em 0.2em 0.2em;}
#messageArea a {text-decoration:underline;}

.tiddlerPopupButton {padding:0.2em 0.2em 0.2em 0.2em;}
.popupTiddler {position: absolute; z-index:300; padding:1em 1em 1em 1em; margin:0;}

.popup {position:absolute; z-index:300; font-size:.9em; padding:0; list-style:none; margin:0;}
.popup .popupMessage {padding:0.4em;}
.popup hr {display:block; height:1px; width:auto; padding:0; margin:0.2em 0em;}
.popup li.disabled {padding:0.4em;}
.popup li a {display:block; padding:0.4em; font-weight:normal; cursor:pointer;}
.listBreak {font-size:1px; line-height:1px;}
.listBreak div {margin:2px 0;}

.tabset {padding:1em 0em 0em 0.5em;}
.tab {margin:0em 0em 0em 0.25em; padding:2px;}
.tabContents {padding:0.5em;}
.tabContents ul, .tabContents ol {margin:0; padding:0;}
.txtMainTab .tabContents li {list-style:none;}
.tabContents li.listLink { margin-left:.75em;}

#contentWrapper {display:block;}
#splashScreen {display:none;}

#displayArea {margin:1em 17em 0em 14em;}

.toolbar {text-align:right; font-size:.9em;}

.tiddler {padding:1em 1em 0em 1em;}

.missing .viewer,.missing .title {font-style:italic;}

.title {font-size:1.6em; font-weight:bold;}

.missing .subtitle {display:none;}
.subtitle {font-size:1.1em;}

.tiddler .button {padding:0.2em 0.4em;}

.tagging {margin:0.5em 0.5em 0.5em 0; float:left; display:none;}
.isTag .tagging {display:block;}
.tagged {margin:0.5em; float:right;}
.tagging, .tagged {font-size:0.9em; padding:0.25em;}
.tagging ul, .tagged ul {list-style:none; margin:0.25em; padding:0;}
.tagClear {clear:both;}

.footer {font-size:.9em;}
.footer li {display:inline;}

.annotation {padding:0.5em; margin:0.5em;}

* html .viewer pre {width:99%; padding:0 0 1em 0;}
.viewer {line-height:1.4em; padding-top:0.5em;}
.viewer .button {margin:0em 0.25em; padding:0em 0.25em;}
.viewer blockquote {line-height:1.5em; padding-left:0.8em;margin-left:2.5em;}
.viewer ul, .viewer ol {margin-left:0.5em; padding-left:1.5em;}

.viewer table, table.twtable {border-collapse:collapse; margin:0.8em 1.0em;}
.viewer th, .viewer td, .viewer tr,.viewer caption,.twtable th, .twtable td, .twtable tr,.twtable caption {padding:3px;}
table.listView {font-size:0.85em; margin:0.8em 1.0em;}
table.listView th, table.listView td, table.listView tr {padding:0px 3px 0px 3px;}

.viewer pre {padding:0.5em; margin-left:0.5em; font-size:1.2em; line-height:1.4em; overflow:auto;}
.viewer code {font-size:1.2em; line-height:1.4em;}

.editor {font-size:1.1em;}
.editor input, .editor textarea {display:block; width:100%; font:inherit;}
.editorFooter {padding:0.25em 0em; font-size:.9em;}
.editorFooter .button {padding-top:0px; padding-bottom:0px;}

.fieldsetFix {border:0; padding:0; margin:1px 0px 1px 0px;}

.sparkline {line-height:1em;}
.sparktick {outline:0;}

.zoomer {font-size:1.1em; position:absolute; overflow:hidden;}
.zoomer div {padding:1em;}

* html #backstage {width:99%;}
* html #backstageArea {width:99%;}
#backstageArea {display:none; position:relative; overflow: hidden; z-index:150; padding:0.3em 0.5em 0.3em 0.5em;}
#backstageToolbar {position:relative;}
#backstageArea a {font-weight:bold; margin-left:0.5em; padding:0.3em 0.5em 0.3em 0.5em;}
#backstageButton {display:none; position:absolute; z-index:175; top:0em; right:0em;}
#backstageButton a {padding:0.1em 0.4em 0.1em 0.4em; margin:0.1em 0.1em 0.1em 0.1em;}
#backstage {position:relative; width:100%; z-index:50;}
#backstagePanel {display:none; z-index:100; position:absolute; margin:0em 3em 0em 3em; padding:1em 1em 1em 1em;}
.backstagePanelFooter {padding-top:0.2em; float:right;}
.backstagePanelFooter a {padding:0.2em 0.4em 0.2em 0.4em;}
#backstageCloak {display:none; z-index:20; position:absolute; width:100%; height:100px;}

.whenBackstage {display:none;}
.backstageVisible .whenBackstage {display:block;}
/*}}}*/
/***
StyleSheet for use when a translation requires any css style changes.
This StyleSheet can be used directly by languages such as Chinese, Japanese and Korean which use a logographic writing system and need larger font sizes.
***/

/*{{{*/
body {font-size:0.8em;}

#sidebarOptions {font-size:1.05em;}
#sidebarOptions a {font-style:normal;}
#sidebarOptions .sliderPanel {font-size:0.95em;}

.subtitle {font-size:0.8em;}

.viewer table.listView {font-size:0.95em;}

.htmlarea .toolbarHA table {border:1px solid ButtonFace; margin:0em 0em;}
/*}}}*/
/*{{{*/
@media print {
#mainMenu, #sidebar, #messageArea, .toolbar, #backstageButton, #backstageArea {display: none ! important;}
#displayArea {margin: 1em 1em 0em 1em;}
/* Fixes a feature in Firefox 1.5.0.2 where print preview displays the noscript content */
noscript {display:none;}
}
/*}}}*/
<!--{{{-->
<div class='header' macro='gradient vert [[ColorPalette::PrimaryLight]] [[ColorPalette::PrimaryMid]]'>
<div class='headerShadow'>
<span class='siteTitle' refresh='content' tiddler='SiteTitle'></span>&nbsp;
<span class='siteSubtitle' refresh='content' tiddler='SiteSubtitle'></span>
</div>
<div class='headerForeground'>
<span class='siteTitle' refresh='content' tiddler='SiteTitle'></span>&nbsp;
<span class='siteSubtitle' refresh='content' tiddler='SiteSubtitle'></span>
</div>
</div>
<div id='mainMenu' refresh='content' tiddler='MainMenu'></div>
<div id='sidebar'>
<div id='sidebarOptions' refresh='content' tiddler='SideBarOptions'></div>
<div id='sidebarTabs' refresh='content' force='true' tiddler='SideBarTabs'></div>
</div>
<div id='displayArea'>
<div id='messageArea'></div>
<div id='tiddlerDisplay'></div>
</div>
<!--}}}-->
<!--{{{-->
<div class='toolbar' macro='toolbar closeTiddler closeOthers +editTiddler > fields syncing permalink references jump'></div>
<div class='title' macro='view title'></div>
<div class='subtitle'><span macro='view modifier link'></span>, <span macro='view modified date'></span> (<span macro='message views.wikified.createdPrompt'></span> <span macro='view created date'></span>)</div>
<div class='tagging' macro='tagging'></div>
<div class='tagged' macro='tags'></div>
<div class='viewer' macro='view text wikified'></div>
<div class='tagClear'></div>
<!--}}}-->
<!--{{{-->
<div class='toolbar' macro='toolbar +saveTiddler -cancelTiddler deleteTiddler'></div>
<div class='title' macro='view title'></div>
<div class='editor' macro='edit title'></div>
<div macro='annotations'></div>
<div class='editor' macro='edit text'></div>
<div class='editor' macro='edit tags'></div><div class='editorFooter'><span macro='message views.editor.tagPrompt'></span><span macro='tagChooser'></span></div>
<!--}}}-->
To get started with this blank TiddlyWiki, you'll need to modify the following tiddlers:
* SiteTitle & SiteSubtitle: The title and subtitle of the site, as shown above (after saving, they will also appear in the browser title bar)
* MainMenu: The menu (usually on the left)
* DefaultTiddlers: Contains the names of the tiddlers that you want to appear when the TiddlyWiki is opened
You'll also need to enter your username for signing your edits: <<option txtUserName>>
These InterfaceOptions for customising TiddlyWiki are saved in your browser

Your username for signing your edits. Write it as a WikiWord (eg JoeBloggs)

<<option txtUserName>>
<<option chkSaveBackups>> SaveBackups
<<option chkAutoSave>> AutoSave
<<option chkRegExpSearch>> RegExpSearch
<<option chkCaseSensitiveSearch>> CaseSensitiveSearch
<<option chkAnimate>> EnableAnimations

----
Also see AdvancedOptions
 Lesson 9
THE AXIAL SKELETON

4-27. INTRODUCTION TO THE HUMAN SKELETON

As a whole, the human skeleton (Figure 4-4) is the supporting framework of the body. The skeleton is composed of the individual bones and the articulations between them. The human skeleton is generally considered in two major subdivisions: the axial skeleton and the appendicular skeleton.



Figure 4-4. Anterior view of the human skeleton.

4-28. INTRODUCTION TO THE AXIAL SKELETON

The axial skeleton (Figure 4-5) is the central supporting framework of the body. Its major components are the vertebral column (spine), the thoracic cage, and the skull.



Figure 4-5. Midsagittal section of skull and vertebral column with CNS and meninges in place.

4-29. SKULL

The skull is the skeleton of the head region. It is located on the top of the vertical vertebral column. It has two major functional subdivisions: the cranium and the facial (visceral) skeleton.

a.      Cranium. The cranium is a spherical container that protects the brain. At the base of the cranium is a series of openings. Blood vessels and nerves enter and leave the cranial cavity through these openings.

b.      Facial Skeleton. The facial skeleton is also referred to as the visceral skull. It is attached to the anterior and inferior surfaces of the cranium. It is the skeleton of the entrances of the respiratory and digestive systems and the orbits containing the eyes.

4-30. NOTE ABOUT THE VERTEBRAL COLUMN

The vertebral column is a series of individual segments, the vertebrae, and one on top of the other.

4-31. MOTIONS OF THE HEAD

The upper part of the vertebral column, the neck region, and associated muscles provide the head with its various motions. The upper two vertebrae are specifically constructed for head motions.

a.      The articulation between the occipital base of the skull and the atlas (the first cervical vertebra) is specially constructed for anterior-posterior motions of the head ("nodding").

b.      Between the atlas (the first cervical vertebra) and the axis (the second cervical vertebra) is a special pivotal-type joint. This joint facilitates rotary (turning) motions of the head.

4-32. WEIGHT BEARING

a.      The vertebral bodies and the associated intervertebral discs are the primary mechanism for supporting the body weight.

b.      In the lumbar and lumbosacral regions, the articular processes of the vertebrae is also weight bearing. (A bony projection extends upward and another extends downward from each right and left side of the neural arch of each of these vertebrae.) These projections are the articular processes. Through them, as well as through the vertebral bodies and discs, adjacent vertebrae are articulated with each other.

c.      The specially constructed sacrum, at the lower end of the vertebral column, receives the body weight from above and transfers it to the pelvic bones of the lower members.

4-33. PROTECTION OF THE SPINAL CORD AND ITS MEMBRANES

Whereas the cranium protects the brain, the neural arches protect the spinal cord and its membranes (meninges). The neural arches of the individual vertebrae arch over the spinal cord and its membranes. The continuous series of neural arches forms a continuous spinal canal.

4-34. MOTION OF THE VERTEBRAL COLUMN
Together, the vertebrae, the intervertebral discs, and the associated ligaments form a semiflexible rod. This allows a certain amount of motion to the vertebral column in addition to its supporting role.

a.      Role of Processes. The spinous and transverse processes of the neural arches serve as attachments for skeletal muscles. By acting as levers, these processes enable the skeletal muscles to move the vertebrae.

b.      Role of Intervertebral Discs. The intervertebral discs between adjacent vertebrae serve several functions. 

(1)        First, they allow motion to occur between adjacent vertebrae. The relative thickness of the individual intervertebral disc determines the amount of motion possible between the adjacent vertebrae. The total movement of the vertebral column (spine) is the sum of the motions of the individual intervertebral discs. 
(2)        Secondly, the intervertebral disc acts as a shock absorber. As such, it minimizes the shocks that are transmitted to the vertebral column by the contact of the heels with the floor during walking, jumping, etc. 
(3)        During the course of a day standing and sitting, the individual becomes about an inch shorter than he was at the beginning of the day. This is less true of older individuals. After a good night's rest in a horizontal position, these discs regain their original thickness. As an astronaut works at zero gravity, he retains his full height. 
(4)        With age, individuals tend to lose height. This is because the intervertebral discs shrink somewhat over the years. Since these discs also become less flexible, there is less compression from morning until night. Thus, the height in the evening is closer to the morning height than with a younger person. 
c. Role of Curvatures of Vertebral Column. As a whole, the vertebral column has four curvatures. Two of these are concave to the front; two are concave to the rear. As do the intervertebral discs, these curvatures function as shock absorbers for the body.

4-35. FUNCTIONS OF THE RIB CAGE

The thoracic cage consists of the ribs, the sternum, and thoracic vertebrae. The 12 pairs of ribs are attached posteriorly to the thoracic vertebrae. Anteriorly, the upper 10 pairs of ribs attach directly or indirectly (via costal cartilages) to the sternum.

a.      Motion. Because of the segmentation of the thoracic cage into vertebrae and ribs, motion can occur in the thoracic region of the body.

b.      Costal Breathing. The special construction of the ribs and their costal cartilages allows costal breathing to take place.

c.      Protection. In addition, the rib cage encloses such vital structures as the lungs, the heart, and the liver and gives them protection.
 [img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0404.jpg]]
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0405.jpg]]
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 Unit 14 Some Elementary Human Genetics

Lessons (select one)
 Topics
 
 Lesson 1  Some Elementary Human Genetics  Introduction - History of Genetics - The Gene - Chromosomes 


 

 

 

 

 
 Learning Objectives

After completing this lesson, you should be able to: 

Identify diploid (2N=46) and haploid (N=23) conditions as related to ordinary body cells, mitotic daughter cells, gametes, and zygotes. 
Define important genetic terms. 
 
 
"Red Pulp" and "White Pulp"
These are two of those troublesome terms that really applicable in gross anatomy, but with which the histologist has to deal as well. Oh, well...here goes:

Cut a freshly-removed spleen across and it looks like a field of dark red material with white spots in it. On the basis of its gross appearance in fresh sections, the spleen is traditionally said to have the bulk of its parenchyma as red pulp, with isolated areas of white pulp interspersed through it. 

The red pulp gets its appearance from the formed elements of the blood (mostly erythrocytes) it contains. The white pulp consists almost entirely of lymphocytes, in a peculiar association with the arterial blood supply (see below). These two terms are quite logical when applied to gross specimens, but things become a little confusing when they're applied to microscopic sections. Briefly, in terms of microscopic sections, "white pulp" is equivalent to the lymphocyte population of the spleen, in the form of the periarteriolar lymphocyte sheath or PALS (see below). "Red pulp" is everything else, which means the splenic cords and the sinuses between them. 
 Lesson 5
A "TYPICAL" FLAT BONE

4-10. GENERAL STRUCTURE

Another category of bones consists of the flat bones. (See Figure 4-2.)


[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0402.jpg]]
Figure 4-2. "Typical" flat bone section.

a.      The flat bones have two layers of dense bony tissue, called tables. Thus, there is an inner table and an outer table.

b.      Generally, between the two tables is a layer of cancellous bony tissue.

(1)     The spaces of this cancellous bony tissue are filled with red marrow. In adults, the red marrow of the flat bones is the primary blood-cell forming area of the body. 
(2)     As with the cancellous tissue of the long bone, the cancellous tissue of the flat bone is organized into trabeculae. The trabeculae are oriented in the same directions as the lines of applied forces, much like the struts of a building. 
(3)     Adjacent to the nasal cavities, many flat bones are hollowed to form the paranasal sinuses. These hollow spaces take the place of cancellous bony tissue. The development of the mastoid bone is likewise formed by the extension of the air-filled cavity of the middle ear into the mastoid bone. 
c.      The outer surface of the outer table and the under surface of the inner table are covered with periosteum. The periosteum is similar to that described for the "typical" long bone.

d.      At their margins, flat bones are articulated with other flat bones and held together by FCT. These fibrous connections are usually called sutures.

4-11. ORIGIN AND DEVELOPMENT

Flat bones generally begin as membranous, FCT models within the fetus. Again, an invasion of material forms an ossification center. This center tears down and replaces the FCT with bone tissue. The ossification center continues to grow outward. In time, a full plate of bone has been formed. Then, the flat bone grows at its margins until adulthood.

4-12. SPECIAL CONDITIONS OF THE FLAT BONES OF THE CRANIUM 

The flat bones of the skull are somewhat special.

a.      Curved Shape. They are generally curved. Together, they form a sphere which surrounds and protects the brain.

b.      Healing of Fractures. When the growth of the cranial flat bones is complete, the osteogenic layer of the periosteum disappears.

(1)        Cracks and/or line fractures of cranial flat bones will usually heal by the activity of the osteoblasts within the bone. 
(2)        However, when bone substance is lost and a spatial defect ("hole") remains, the missing portions of the table(s) will not be replaced. Osteoblastic activity will repair only the margins of the spatial defect ("hole"). 
c.      Variations in Brain Injury.

(1)        In a young individual, the flat bones of the skull are not yet fully developed. The cranium as a whole is relatively flexible. An injury to the brain, resulting from a force applied to the cranium, will usually be located immediately below the location of the applied force. 
(2)        In an older adult, the flat bones of the skull have fully developed and are more or less fused to each other. The cranium is a relatively solid sphere. An injury to the brain, resulting from a force applied to the cranium, will usually be found on the opposite side from the applied force. Often, the applied force will be diverted around the sphere to the base of the cranium. There, the diverted force may cause fractures of the cranium at the apertures (openings) in its base.  
Lesson 4
A "TYPICAL" LONG BONE

4-8. GENERAL STRUCTURE

A "typical" long bone, as the name implies, has more length than width. (See Figure 4-1.)
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0401.jpg]]


Figure 4-1. "Typical" long bone section.

a. Shaft (Diaphysis). In effect, the long bone has a shaft, with proximal and distal ends. The shaft tends to be cylindrical in form. 

(1)        It has a cortex (outer portion) of dense bony tissue called compact bone tissue. The cortex is usually thickest at the middle of the shaft. 
(2)        The inside of the shaft is usually hollow, except that it is filled with yellow marrow (in adults, but red marrow in small children and infants). 
b. Ends (Epiphyses). At the ends of the long bone, the cortex is much thinner. Each end is filled with a lattice-or sponge-like network of bony tissue, called cancellous bony tissue. The strands of bone forming this lattice are called trabeculae. The trabeculae are aligned with the lines of applied forces, particularly tension and compression. The spaces within the cancellous bony tissue are filled with red marrow.

c. Some Special Parts. The skeletal muscles pull and create tensions at their attachments to the bone. These tensions will often cause the bone to react and form spines, tubercles, ridges, and the like.

d. Articular Cartilages. The surface of each end of the bone is covered by an articular cartilage. This cartilage is located where the bone contacts another bone at a joint. The cartilage is made up of hyaline-type cartilage tissue. The articular cartilage makes the movement between the bones smoother.

e. Periosteum. The periosteum surrounds the bone, except where the articular cartilages are located. The periosteum is an envelope of the bone and consists mainly of dense FCT. In fact, the periosteum may be considered the outermost portion of the bone. 

(1)        However, the periosteum has a special layer of cells immediately adjacent to the surface of the bone. Since this layer is able to produce bone material, it is called the osteogenic layer of the periosteum. 
(2)        When a long bone is fractured or a portion of the bone is lost without losing the periosteum, the fracture is healed by the combined action of the osteogenic layer of the periosteum and the osteoblasts of the bone itself. 
f. NAVL. Associated with the periosteum are the "service tissues." These are the NAVL (nerves, arteries, veins, and lymphatics), which nourish and stimulate the living tissues of the bone and periosteum. 

(1) Neurovascular bundle. Branches from the main NAVL of the body go as a unit to the bone. This unit, the neurovascular bundle, consists of NAVL within a common fibrous connective sheath. 
(2) Branches of neurovascular bundle. Portions of these NAVL spread out through the periosteum as periosteal branches over the outer surfaces of the bone. Other branches penetrate through the cortex of the bone to spread out through the medullary (or marrow) cavity. The holes through the cortex are known as the nutrient canals. The branches are known as the nutrient branches. 
4-9. ORIGIN AND DEVELOPMENT

a.      A long bone begins in the fetus as a hyaline cartilage model of the bone.

b.      At the appropriate time, the cartilage model is invaded by a mass of material that begins to destroy the cartilage and replace it with bone tissue. This invading mass and the subsequently developed bone structure are called the primary center of ossification, or diaphysis.

c.      At about the time of birth or thereafter, a secondary center of ossification, or epiphysis, develops at each end of the developing long bone.

d.      A plate of cartilage, called the epiphyseal plate, remains between the diaphysis and each epiphysis. In the early years of life, the cartilage grows faster than the diaphysis can tear it down. This results in gradual lengthening of the long bone.

e.      At the proper time, between puberty and adulthood, the bone development overtakes completely destroys the cartilage. After this, the diaphysis and the epiphysis are solidly fused to one another. The dense bony line of fusion between the diaphysis and epiphysis is called the epiphyseal line. The epiphyseal line is easily visible in the radiographs ("x-rays") of young adults.

f.        While the bone has been growing in length, it also grows in width. The osteogenic layer of the periosteum gradually adds bony tissue to the outside surface of the bone. At the same time, osteoclastic activity removes bone material from the wall of the marrow cavity.

g.      Many factors are involved in the process of bone growth. One of the primary factors is a hormone of the anterior pituitary gland known as somatotropin. Overproduction of somatotropin in a young person (before fusion of the ossification centers) results in gigantism. Overproduction of somatotropin in adults (after fusion of the ossification centers) results in a condition called acromegaly. Acromegaly involves excessive growth of the jaw, hands, and feet.

h.      Throughout the entire life of the individual, the continuous tearing down (osteoclastic activity) and rebuilding (osteoblastic activity) remodel the bony substance. These processes occur in response to the forces or stresses applied to the body.
 Lesson 8
A "TYPICAL" SYNOVIAL JOINT

4-19. INTRODUCTION

A synovial joint is structured to facilitate freedom of motion in one or more of the three planes around the three axes of any given joint. The "typical" synovial joint (Figure 4-3) is a schematic representation rather than an actual synovial joint, but it contains the structural features common to all synovial joints.

4-20. BONES

The synovial articulation is formed between two bones. These bones are parts of the skeleton. They are levers of motion. To them are attached skeletal muscles, which provide the forces for motion.



Figure 4-3. A "typical" synovial joint--diagrammatic. 

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0403.jpg]]


4-21. ARTICULAR CARTILAGES

Covering a portion of each bone is an articular cartilage. The portions covered are the ends that would otherwise be in contact during the motions of the joint. Each articular cartilage has a relatively smooth surface and some ability to act as a shock absorber.

4-22. JOINT CAPSULE

The joint area is surrounded by a dense FCT capsule that encloses the joint area.

4-23. SYNOVIAL MEMBRANE, FLUID, AND CAVITY

The inner surface of this fibrous capsule is lined with a synovial membrane. The synovial membrane secretes a synovial fluid into the synovial cavity, or joint space. The synovial fluid is a very good lubricant. Thus, it minimizes the frictional forces between the moving bones.

4-24. LIGAMENTS

The bones of the synovial joint are held together by ligaments. Ligaments are very dense FCT structures that keep the bones from being pulled apart. These ligaments may occur as either discrete, individual structures or as thickenings of the fibrous capsule.

4-25. SKELETAL MUSCLES

The skeletal muscles cross the synovial joint from one bone to the other. They are attached to the bones. The tonic (continuous) contraction of these skeletal muscles holds the opposing surfaces of the bones tightly together. When properly stimulated, these muscles contract and cause motion of the bones around the joint.

4-26. TYPES OF SYNOVIAL JOINTS

Synovial joints are often referred to by their geometric or mechanical structure.

a.      Ball-and-Socket Joint. The ball-and-socket synovial joint has one bone with a rounded head, a "ball." The other bone has a corresponding cavity, the "socket." The ball-and-socket joint is usually multiaxial.

b.      Hinge Joint. In the hinge joint, the geometry of the bony surfaces and the disposition of the ligaments are such as to allow the parts to fold on each other, around a single axis only.

c.      Others. There are other special arrangements of the synovial joints to produce specific motions. An example: Rotation of the head at the pivot-type joint of atlas and axis (the upper two vertebrae).
 
Started work on Unit Four, The Muscles, today.
Started this Wiki.
test
A Phone Number
 
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Anatomy and Physiology 101

[[Unit One]]
[[Unit Two]]
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[[Unit Four]]
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[[Review]]
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Anatomy and Physiology 101

[[Unit One]]
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[[Unit Nine]]
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[[Unit Eleven]]
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[[Review]]
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Adenosine diphosphate
From Wikipedia, the free encyclopedia
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Adenosine diphosphate 
 
Identifiers 
CAS number 58-64-0 
PubChem 197 
SMILES Nc1ncnc2[n](cnc12)[C@@H]3O[C@H]
(COP([O-])(=O)OP(O)([O-])=O)C(O)C3O 
Properties 
Molecular formula C10H15N5O10P2 
Molar mass 427.201 
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references 
Adenosine diphosphate, abbreviated ADP, is a nucleotide. It is an ester of pyrophosphoric acid with the nucleotide adenine. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine.

ADP is the product of ATP dephosphorylation by ATPases. ADP is converted back to ATP by ATP synthases. ATP is an important energy transfer molecule in cells.

ADP is stored in platelet dense granules and is released upon platelet activation. ADP interacts with a family of ADP receptors found on platelets (P2Y1, P2Y12 and P2X1), leading to further platelet activation.[1] ADP in the blood is converted to adenosine by the action of ecto-ADPases, inhibiting further platelet activation via adenosine receptors. The anti-platelet drug Plavix (clopidogrel) inhibits the P2Y12 receptor.


[edit] See also
Nucleoside 
Nucleotide 
DNA 
RNA 
Oligonucleotide 
Adenosine triphosphate 
Apyrase 

[edit] References
^ Murugappa S, Kunapuli SP, "The role of ADP receptors in platelet function", Front Biosci., 2006, 11:1977-86 

[edit] External links



v • d • eMajor families of biochemicals 
Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides 
Analogues of nucleic acids: Types of Nucleic Acids Analogues of nucleic acids: 
Nucleobases: Purine (Adenine, Guanine) | Pyrimidine (Uracil, Thymine, Cytosine) 
Nucleosides: Adenosine/Deoxyadenosine | Guanosine/Deoxyguanosine | Uridine | Thymidine | Cytidine/Deoxycytidine 
Nucleotides: monophosphates (AMP, UMP, GMP, CMP) | diphosphates (ADP, UDP, GDP, CDP) | triphosphates (ATP, UTP, GTP, CTP) | cyclic (cAMP, cGMP, cADPR) 
Deoxynucleotides: monophosphates (dAMP, TMP, dGMP, dCMP) | diphosphates (dADP, TDP, dGDP, dCDP) | triphosphates (dATP, TTP, dGTP, dCTP) 
Ribonucleic acids: RNA | mRNA | piRNA | tRNA | rRNA | ncRNA | gRNA | shRNA | siRNA | snRNA | miRNA | snoRNA 
Deoxyribonucleic acids: DNA | mtDNA | cDNA | plasmid | Cosmid | BAC | YAC | HAC 
Analogues of nucleic acids: GNA | PNA | TNA | Morpholino | LNA 




  This biochemistry article is a stub. You can help Wikipedia by expanding it. 

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Study

Anatomy and Physiology 101

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[[Review]]
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Adenosine triphosphate
From Wikipedia, the free encyclopedia
• Interested in contributing to Wikipedia? •Jump to: navigation, search
Adenosine 5'-triphosphate 



 
Chemical name




 5-(6-aminopurin-9-yl)
-3,4-dihydroxy-oxolan-2-yl
methoxy-hydroxy-phosphoryl
oxy-hydroxy-phosphoryl oxyphosphonic acid 
Abbreviations ATP
 
Chemical formula C10H16N5O13P3 
Identifiers 
CAS number  
SMILES Nc1ncnc2[n](cnc12)
[C@@H]3O[C@H]
(COP([O-])(=O)OP([O-])
(=O)OP([O-])
([O-])=O)C(O)C3O 
Molecular mass 507.181 g mol-1 
Melting point  ? 
Density  ? 
pKa 6.5 (secondary phosphate) 
CAS number 56-65-5 
EINECS 200-283-2 
PubChem 5957 
Adenosine 5'-triphosphate (ATP) is a multifunctional nucleotide that is most important as a "molecular currency" of intracellular energy transfer. In this role, ATP transports chemical energy within cells for metabolism. It is produced as an energy source during the processes of photosynthesis and cellular respiration and consumed by many enzymes and a multitude of cellular processes including biosynthetic reactions, motility and cell division. In signal transduction pathways, ATP is used as a substrate by kinases that phosphorylate proteins and lipids, as well as by adenylate cyclase, which uses ATP to produce the second messenger molecule cyclic AMP.

The structure of this molecule consists of a purine base (adenine) attached to the 1' carbon atom of a pentose sugar (ribose). Three phosphate groups are attached at the 5' carbon atom of the pentose sugar. ATP is also incorporated into nucleic acids by polymerases in the processes of DNA replication and transcription. When ATP is used in DNA synthesis, the ribose sugar is first converted to deoxyribose by ribonucleotide reductase. ATP was discovered in 1929 by Karl Lohmann,[1] and was proposed to be the main energy-transfer molecule in the cell by Fritz Albert Lipmann in 1941.[2]

Contents [hide]
1 Physical and chemical properties 
1.1 Ionization in biological systems 
2 Biosynthesis 
2.1 Glycolysis 
2.2 Citric acid cycle 
2.3 Beta-oxidation 
2.4 Anaerobic respiration 
2.5 ATP replenishment by nucleoside diphosphate kinases 
2.6 ATP production during photosynthesis 
2.7 ATP recycling 
3 Regulation of biosynthesis 
4 Functions in cells 
4.1 Cell signaling 
4.1.1 Extracellular signaling 
4.1.2 Intracellular signaling 
4.2 Deoxyribonucleotide synthesis 
5 Binding to proteins 
6 ATP analogs 
7 See also 
8 References 
9 External links 
 


[edit] Physical and chemical properties
ATP consists of adenosine—itself composed of an adenine ring and a ribose sugar—and three phosphate groups (triphosphate). The phosphoryl groups, starting with the group closest to the ribose, are referred to as the alpha (α), beta (β), and gamma (γ) phosphates. ATP is highly soluble in water and is quite stable in solutions between pH 6.8–7.4, but is rapidly hydrolysed at extreme pH, consequently ATP is best stored as an anhydrous salt.[3]

As ATP is an unstable molecule it tends to be hydrolysed in water, and if ATP and ADP are allowed to come to chemical equilibrium, almost all the ATP will be converted to ADP. Any system that is far from equilibrium contains potential energy, and is capable of doing work. The cell maintains the ratio of ATP to ADP at a point ten orders of magnitude from equilibrium, with ATP concentrations a thousandfold higher than the concentration of ADP. This displacement from equilibrium means that the hydrolysis of ATP in the cell releases a great deal of energy.[4] ATP is commonly referred to as a "high energy molecule", however a mixture of ATP and ADP at equilibrium in water can do no useful work at all. In fact, ATP does not contain any special "high-energy bonds" and any other unstable molecule would serve equally well as a way of storing energy if the cell maintained its concentration far from equilibrium.

The amount of energy released can be calculated from the changes in energy under non-natural conditions. The net change in heat energy (enthalpy) at standard temperature and pressure of the decomposition of ATP into hydrated ADP and hydrated inorganic phosphate is −20.5 kJ / mole, with a change in free energy of 3.4 kJ/mole.[5] The energy released by cleaving either a phosphate (Pi) or pyrophosphate (PPi) unit from ATP, with all reactants and products at their standard states of 1 M concentration, are:

ATP + H2O → ADP(hydrated) + Pi(hydrated) + H+(hydrated) ΔG˚ = -30.54 kJ/mol (−7.3 kcal/mol) 
ATP + H2O → AMP(hydrated) + PPi(hydrated) + H+(hydrated) ΔG˚ = -45.6 kJ/mol (−10.9 kcal/mol) 
These values can be used to calculate the change in energy under physiological conditions and the cellular ATP/ADP ratio. Note the values given for the Gibbs free energy for this reaction are dependent on a number of factors, including overall ionic strength and the presence of alkaline earth metal ions such as Mg2+ and Ca2+. Under typical cellular conditions, ΔG is approximately −57 kJ/mol (−14 kcal/mol).[6]


[edit] Ionization in biological systems
ATP has multiple ionizable groups with different acid dissociation constants. In neutral solution, ATP is ionized and exists mostly as ATP4−, with a small proportion of ATP3−.[7] As ATP has several negatively-charged groups in neutral solution, it can chelate metals with very high affinity. The binding constant for various metal ions are (given as per mole) as Mg2+ (9 554), Na+ (13), Ca2+ (3 722), K+ (8), Sr2+ (1 381) and Li+ (25).[8] Due to the strength of these interactions, ATP exists in the cell mostly in a complex with Mg2+.[9][7]

 
Space-filling model of ATP 
Ball-and-stick model of ATP
[edit] Biosynthesis
The ATP concentration inside the cell is typically 1 - 10 mM. ATP can be produced by redox reactions using simple and complex sugars (carbohydrates) or lipids as an energy source. For ATP to be synthesized from complex fuels, they first need to be broken down into their basic components. Carbohydrates are hydrolysed into simple sugars, such as glucose and fructose. Fats (triglycerides) are metabolised to give fatty acids and glycerol.

The overall process of oxidizing glucose to carbon dioxide is known as cellular respiration and can produce up to 36 molecules of ATP from a single molecule of glucose.[10] ATP can be produced by a number of distinct cellular processes; the three main pathways used to generate energy in eukaryotic organisms are glycolysis and the citric acid cycle/oxidative phosphorylation , both components of cellular respiration; and beta-oxidation. The majority of this ATP production by a non-photosynthetic aerobic eukaryote takes place in the mitochondria, which can make up nearly 25% of the total volume of a typical cell.[10]


[edit] Glycolysis
Main article: glycolysis
In glycolysis, glucose and glycerol are metabolized to pyruvate via the glycolytic pathway. In most organisms this process occurs in the cytosol, but in some protozoa such as the kinetoplastids, this is carried out in a specialized organelle called the glycosome.[11] Glycolysis generates a net two molecules of ATP through substrate phosphorylation catalyzed by two enzymes: PGK and pyruvate kinase. Two molecules of NADH are also produced, which can be oxidized via the electron transport chain and result in the generation of additional ATP by ATP synthase. The pyruvate generated as an end-product of glycolysis is a substrate for the Krebs Cycle.


[edit] Citric acid cycle
Main articles: Citric acid cycle and oxidative phosphorylation
In the mitochondrion, pyruvate is oxidized by the pyruvate dehydrogenase complex to acetyl CoA, which is fully oxidized to carbon dioxide by the citric acid cycle (also known as the Krebs Cycle). Every "turn" of the citric acid cycle produces two molecules of carbon dioxide, one molecule of the ATP equivalent guanosine triphosphate (GTP) through substrate-level phosphorylation catalyzed by succinyl CoA synthetase, three molecules of the reduced coenzyme NADH, and one molecule of the reduced coenzyme FADH2. Both of these latter molecules are recycled to their oxidized states (NAD+ and FAD, respectively) via the electron transport chain, which generates additional ATP by oxidative phosphorylation. The oxidation of an NADH molecule results in the synthesis of about 3 ATP molecules, and the oxidation of one FADH2 yields about 2 ATP molecules.[12] The majority of cellular ATP is generated by this process. Although the citric acid cycle itself does not involve molecular oxygen, it is an obligately aerobic process because O2 is needed to recycle the reduced NADH and FADH2 to their oxidized states. In the absence of oxygen the citric acid cycle will cease to function due to the lack of available NAD+ and FAD.[10]

The generation of ATP by the mitochondrion from cytosolic NADH relies on the malate-aspartate shuttle (and to a lesser extent, the glycerol-phosphate shuttle) because the inner mitochondrial membrane is impermeable to NADH and NAD+. Instead of transferring the generated NADH, a malate dehydrogenase enzyme converts oxaloacetate to malate, which is translocated to the mitochondrial matrix. Another malate dehydrogenase-catalyzed reaction occurs in the opposite direction, producing oxaloacetate and NADH from the newly transported malate and the mitochondrion's interior store of NAD+. A transaminase converts the oxaloacetate to aspartate for transport back across the membrane and into the intermembrane space.[10]

In oxidative phosphorylation, the passage of electrons from NADH and FADH2 through the electron transport chain powers the pumping of protons out of the mitrochondrial matrix and into the intermembrane space. This creates a proton motive force that is the net effect of a pH gradient and an electric potential gradient across the inner mitochondrial membrane. Flow of protons down this potential gradient - that is, from the intermembrane space to the matrix - provides the driving force for ATP synthesis by ATP synthase. This enzyme contains a rotor subunit that physically rotates relative to the static portions of the protein during ATP synthesis.[13]

Most of the ATP synthesized in the mitochondria will be used for cellular processes in the cytosol; thus it must be exported from its site of synthesis in the mitochondrial matrix. The inner membrane contains antiporters that are integral membrane proteins used to exchange newly-synthesized ATP in the matrix for ADP in the intermembrane space.[14]


[edit] Beta-oxidation
Main article: beta-oxidation
Fatty acids can also be broken down to acetyl-CoA by beta-oxidation. Each turn of this cycle reduces the length of the acyl chain by two carbon atoms and produces one NADH and one FADH2 molecule, which are used to generate ATP by oxidative phosphorylation. Because NADH and FADH2 are energy-rich molecules, dozens of ATP molecules can be generated by the beta-oxidation of a single long acyl chain. The high energy yield of this process and the compact storage of fat explain why it is the most dense source of dietary calories.[15]


[edit] Anaerobic respiration
Main article: anaerobic respiration
Anaerobic respiration or fermentation entails the generation of energy via the process of oxidation in the absence of O2 as an electron acceptor. In most eukaryotes, glucose is used as both an energy store and an electron donor. The equation for the oxidation of glucose to lactic acid is:

C6H12O6  2CH3CH(OH)COOH + 2 ATP 
In prokaryotes, multiple electron acceptors can be used in anaerobic respiration. These include nitrate, sulfate or carbon dioxide. These processes lead to the ecologically-important processes of denitrification, sulfate reduction and acetogenesis, respectively.[16][17]


[edit] ATP replenishment by nucleoside diphosphate kinases
ATP can also be synthesized through several so-called "replenishment" reactions catalyzed by the enzyme families of nucleoside diphosphate kinases (NDKs), which use other nucleoside triphosphates as a high-energy phosphate donor, and the ATP:guanido-phosphotransferase family, which uses creatine.

ADP + GTP  ATP + GDP 

[edit] ATP production during photosynthesis
In plants, ATP is synthesized in thylakoid membrane of the chloroplast during the light-dependent reactions of photosynthesis in a process called photophosphorylation. Here, light energy is used to pump protons across the chloroplast membrane. This produces a proton-motive force and this drives the ATP synthase, exactly as in oxidative phosphorylation.[18] Some of the ATP produced in the chloroplasts is consumed in the Calvin cycle, which produces triose sugars.


[edit] ATP recycling
The total quantity of ATP in the human body is about 0.1 mole. The majority of ATP is not usually synthesised de novo, but is generated from ADP by the aforementioned processes. Thus, at any given time, the total amount of ATP + ADP remains fairly constant.

The energy used by human cells requires the hydrolysis of 100 to 150 moles of ATP daily which is around 50 to 75 kg. Typically, a human will use up their body weight of ATP over the course of the day.[19] This means that each ATP molecule is recycled 1000 to 1500 times during a single day (100 / 0.1 = 1000). ATP cannot be stored, hence its consumption closely follows its synthesis.


[edit] Regulation of biosynthesis
ATP production in an aerobic eukaryotic cell is tightly regulated by allosteric mechanisms, by feedback effects, and by the substrate concentration dependence of individual enzymes within the glycolysis and oxidative phosphorylation pathways. Key control points occur in enzymatic reactions that are so energetically favorable that they are effectively irreversible under physiological conditions.

In glycolysis, hexokinase is directly inhibited by its product, glucose-6-phosphate, and pyruvate kinase is inhibited by ATP itself. The main control point for the glycolytic pathway is phosphofructokinase (PFK), which is allosterically inhibited by high concentrations of ATP and activated by high concentrations of AMP. The inhibition of PFK by ATP is unusual, since ATP is also a substrate in the reaction catalyzed by PFK; the biologically active form of the enzyme is a tetramer that exists in two possible conformations, only one of which binds the second substrate fructose-6-phosphate (F6P). The protein has two binding sites for ATP - the active site is accessible in either protein conformation, but ATP binding to the inhibitor site stabilizes the conformation that binds F6P poorly.[12] A number of other small molecules can compensate for the ATP-induced shift in equilibrium conformation and reactivate PFK, including cyclic AMP, ammonium ions, inorganic phosphate, and fructose 1,6 and 2,6 biphosphate.[12]

The citric acid cycle is regulated mainly by the availability of key substrates, particularly the ratio of NAD+ to NADH and the concentrations of calcium, inorganic phosphate, ATP, ADP, and AMP. Citrate - the molecule that gives its name to the cycle - is a feedback inhibitor of citrate synthase and also inhibits PFK, providing a direct link between the regulation of the citric acid cycle and glycolysis.[12]

In oxidative phosphorylation, the key control point is the reaction catalyzed by cytochrome c oxidase, which is regulated by the availability of its substrate—the reduced form of cytochrome c. The amount of reduced cytochrome c available is directly related to the amounts of other substrates:

 
which directly implies this equation:

 
Thus, a high ratio of [NADH] to [NAD+] or a low ratio of [ADP][Pi] to [ATP] imply a high amount of reduced cytochrome c and a high level of cytochrome c oxidase activity.[12] An additional level of regulation is introduced by the transport rates of ATP and NADH between the mitochondrial matrix and the cytoplasm.[14]


[edit] Functions in cells
ATP is generated in the cell by energy-releasing processes and is broken down by energy-consuming processes, in this way ATP transfers energy between spatially-separate metabolic reactions. ATP is the main energy source for the majority of cellular functions. This includes the synthesis of macromolecules, including DNA, RNA, and proteins. ATP also plays a critical role in the transport of macromolecules across cell membranes, e.g. exocytosis and endocytosis.

ATP is critically involved in maintaining cell structure by facilitating assembly and disassembly of elements of the cytoskeleton. In a related process, ATP is required for the shortening of actin and myosin filament crossbridges required for muscle contraction. This latter process is one of the main energy requirements of animals and is essential for locomotion and respiration.


[edit] Cell signaling

[edit] Extracellular signaling
ATP is also a signaling molecule. ATP, ADP, or adenosine are recognized by purinergic receptors.

In humans, this signaling role is important in both the central and peripheral nervous system. Activity-dependent release of ATP from synapses, axons and glia activates purinergic membrane receptors known as P2.[20] The P2Y receptors are metabotropic, i.e. G protein-coupled and modulate mainly intracellular calcium and sometimes cyclic AMP levels. Fifteen members of the P2Y family have been reported (P2Y1–P2Y15), although some are only related through weak homology and several (P2Y5, P2Y7, P2Y9, P2Y10) do not function as receptors that raise cytosolic calcium. The P2X ionotropic receptor subgroup comprises seven members (P2X1–P2X7) which are ligand-gated Ca2+-permeable ion channels that open when bound to an extracellular purine nucleotide. In contrast to P2 receptors (agonist order ATP > ADP > AMP > ADO), purinergic nucleotides like ATP are not strong agonists of P1 receptors which are strongly activated by adenosine and other nucleosides (ADO > AMP > ADP > ATP). P1 receptors have A1, A2a, A2b, and A3 subtypes ("A" as a remnant of old nomenclature of adenosine receptor), all of which are G protein-coupled receptors, A1 and A3 being coupled to Gi, and A2a and A2b being coupled to Gs.[21]


[edit] Intracellular signaling
ATP is critical in signal transduction processes. It is used by kinases as the source of phosphate groups in their phosphate transfer reactions. Kinase activity on substrates such as proteins or membrane lipids are a common form of signal transduction. Phosphorylation of a protein by a kinase can activate this cascade such as the mitogen-activated protein kinase cascade.[22]

ATP is also used by adenylate cyclase and is transformed to the second messenger molecule cyclic AMP, which is involved in triggering calcium signals by the release of calcium from intracellular stores.[23] This form of signal transduction is particularly important in brain function, although it is involved in the regulation of a multitude of other cellular processes.[24]


[edit] Deoxyribonucleotide synthesis
In all known organisms, the deoxyribonucleotides that make up DNA are synthesized by the action of ribonucleotide reductase (RNR) enzymes on their corresponding ribonucleotides.[25] This enzyme reduces the 2' hydroxyl group on the ribose sugar to deoxyribose, forming a deoxyribonucleotide (denoted dATP). All ribonucleotide reductase enzymes use a common sulfhydryl radical mechanism reliant on reactive cysteine residues that oxidize to form disulfide bonds in the course of the reaction.[25] RNR enzymes are recycled by reaction with thioredoxin or glutaredoxin.[12]

The regulation of RNR and related enzymes maintains a balance of dNTPs relative to each other and relative to NTPs in the cell. Very low dNTP concentration inhibits DNA synthesis and DNA repair and is lethal to the cell, while an abnormal ratio of dNTPs is mutagenic due to the increased likelihood of misincorporating a dNTP during DNA synthesis.[12] Regulation of or differential specificity of RNR has been proposed as a mechanism for alterations in the relative sizes of intracellular dNTP pools under cellular stress such as hypoxia.[26]


[edit] Binding to proteins
 
An example of the Rossmann fold, a structural domain of a decarboxylase enzyme from the bacterium Staphylococcus epidermidis (PDB ID 1G5Q) with a bound flavin mononucleotide cofactor.Some proteins that bind ATP do so in a characteristic protein fold known as the Rossmann fold, which is a general nucleotide-binding structural domain that can also bind the cofactor NAD.[27] The most common ATP-binding proteins, known as kinases, share a small number of common folds; the protein kinases, the largest kinase superfamily, all share common structural features specialized for ATP binding and phosphate transfer.[28]

ATP in complexes with proteins generally requires the presence of a divalent cation, almost always magnesium, which binds to the ATP phosphate groups. The presence of magnesium greatly decreases the dissociation constant of ATP from its protein binding partner without affecting the ability of the enzyme to catalyze its reaction once the ATP has bound.[29] The presence of magnesium ions can serve as a mechanism for kinase regulation.[30]


[edit] ATP analogs
Biochemistry laboratories often use in vitro studies to explore ATP-dependent molecular processes. Enzyme inhibitors of ATP-dependent enzymes such as kinases are needed to examine the binding sites and transition states involved in ATP-dependent reactions. ATP analogs are also used in X-ray crystallography to determine a protein structure in complex with ATP, often together with other substrates.

Most useful ATP analogs cannot be hydrolyzed as ATP would be; instead they trap the enzyme in a structure closely related to the ATP-bound state. Adenosine 5'-(gamma-thiotriphosphate) is an extremely common ATP analog in which one of the gamma-phosphate oxygens is replaced by a sulfur atom; this molecule is hydrolyzed at a dramatically slower rate than ATP itself and functions as an inhibitor of ATP-dependent processes. In crystallographic studies, hydrolysis transition states are modeled by the bound vanadate ion. However, caution is warranted in interpreting the results of experiments using ATP analogs, since some enzymes can hydrolyze them at appreciable rates at high concentration.[31]


[edit] See also
Adenosine diphosphate (ADP) 
Adenosine monophosphate (AMP) 
Cyclic adenosine monophosphate (cAMP) 
ATPases 
ATP hydrolysis 
Citric acid cycle (also called the Krebs cycle or TCA cycle) 
Phosphagen 
Nucleotide exchange factor 
Mitochondria 
Photophosphorylation 

[edit] References
^ Lohmann, K. (1929) Naturwissenschaften 17, 624–625 
^ Lipman F. (1941) Adv. Enzymol. 1, 99-162. 
^ Stecher P.G., (1968) The Merck Index 8th edition, Merck and Co. Ltd. 
^ Nicholls D.G. and Ferguson S.J. (2002) Bioenergetics Academic press 3rd edition ISBN 0-125-18121-3 
^ Gajewski E, Steckler D, Goldberg R (1986). "Thermodynamics of the hydrolysis of adenosine 5'-triphosphate to adenosine 5'-diphosphate". J Biol Chem 261 (27): 12733–7. PMID 3528161.  
^ Stryer, Lubert (2002). Biochemistry, fifth edition. New York: W.H. Freeman and Company. ISBN 0-7167-1843-X.  
^ a b Storer A, Cornish-Bowden A (1976). "Concentration of MgATP2− and other ions in solution. Calculation of the true concentrations of species present in mixtures of associating ions.". Biochem J 159 (1): 1–5. PMID 11772.  
^ Wilson J, Chin A (1991). "Chelation of divalent cations by ATP, studied by titration calorimetry". Anal Biochem 193 (1): 16–9. PMID 1645933.  
^ Garfinkel L, Altschuld R, Garfinkel D (1986). "Magnesium in cardiac energy metabolism". J Mol Cell Cardiol 18 (10): 1003–13. PMID 3537318.  
^ a b c d Lodish, H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipursky SL, Darnell J. (2004). Molecular Cell Biology, 5th, New York: WH Freeman. 
^ Parsons M (2004). "Glycosomes: parasites and the divergence of peroxisomal purpose". Mol Microbiol 53 (3): 717-24. PMID 15255886.  
^ a b c d e f g Voet D, Voet JG. (2004). Biochemistry Vol 1 3rd ed. Wiley: Hoboken, NJ. 
^ Abrahams J, Leslie A, Lutter R, Walker J (1994). "Structure at 2.8 A resolution of F1-ATPase from bovine heart mitochondria". Nature 370 (6491): 621-8. PMID 8065448.  
^ a b Dahout-Gonzalez C, Nury H, Trézéguet V, Lauquin G, Pebay-Peyroula E, Brandolin G. "Molecular, functional, and pathological aspects of the mitochondrial ADP/ATP carrier". Physiology (Bethesda) 21: 242-9. PMID 16868313.  
^ Ronnett G, Kim E, Landree L, Tu Y (2005). "Fatty acid metabolism as a target for obesity treatment". Physiol Behav 85 (1): 25-35. PMID 15878185.  
^ Zumft W (1997). "Cell biology and molecular basis of denitrification". Microbiol Mol Biol Rev 61 (4): 533 – 616. PMID 9409151.  
^ Drake H, Daniel S, Küsel K, Matthies C, Kuhner C, Braus-Stromeyer S (1997). "Acetogenic bacteria: what are the in situ consequences of their diverse metabolic versatilities?". Biofactors 6 (1): 13 – 24. PMID 9233536.  
^ Allen J (2002). "Photosynthesis of ATP-electrons, proton pumps, rotors, and poise.". Cell 110 (3): 273-6. PMID 12176312.  
^ Di Carlo, S. E. and Coliins, H. L. (2001) Advan. Physiol. Edu. 25: 70-71. [1] 
^ Fields, R.D. and Burnstock G. 2006. Purinergic signalling in neuron-glia interactions. Nature Reviews Neuroscience 7: 423-436. 
^ Fredholm, BB, Abbracchio, MP, Burnstock, G, Daly, JW, Harden, TK, Jacobson, KA, Leff, P, Williams, M Nomenclature and classification of purinoceptors Pharmacol Rev 1994 46: 143-156[2] 
^ Mishra N, Tuteja R, Tuteja N (2006). "Signaling through MAP kinase networks in plants". Arch Biochem Biophys 452 (1): 55-68. PMID 16806044.  
^ Kamenetsky M, Middelhaufe S, Bank E, Levin L, Buck J, Steegborn C (2006). "Molecular details of cAMP generation in mammalian cells: a tale of two systems.". J Mol Biol 362 (4): 623-39. PMID 16934836.  
^ Hanoune J, Defer N. "Regulation and role of adenylyl cyclase isoforms". Annu Rev Pharmacol Toxicol 41: 145-74. PMID 11264454.  
^ a b Stubbe J (1990). "Ribonucleotide reductases: amazing and confusing". J Biol Chem 265 (10): 5329-32. PMID 2180924.  
^ Chimploy K, Tassotto M, Mathews C (2000). "Ribonucleotide reductase, a possible agent in deoxyribonucleotide pool asymmetries induced by hypoxia". J Biol Chem 275 (50): 39267-71. PMID 11006282.  
^ Rao S, Rossmann M (1973). "Comparison of super-secondary structures in proteins". J Mol Biol 76 (2): 241-56. PMID 4737475.  
^ Scheeff E, Bourne P (2005). "Structural evolution of the protein kinase-like superfamily". PLoS Comput Biol 1 (5): e49. PMID 16244704.  
^ Saylor P, Wang C, Hirai T, Adams J (1998). "A second magnesium ion is critical for ATP binding in the kinase domain of the oncoprotein v-Fps". Biochemistry 37 (36): 12624-30. PMID 9730835.  
^ Lin X, Ayrapetov M, Sun G. "Characterization of the interactions between the active site of a protein tyrosine kinase and a divalent metal activator". BMC Biochem 6: 25. PMID 16305747.  
^ Resetar AM, Chalovich JM. (1995). Adenosine 5'-(gamma-thiotriphosphate): an ATP analog that should be used with caution in muscle contraction studies. 34(49):16039-45. 

[edit] External links
http://en.wikipedia.org/wiki/Acetyl-CoA

Acetyl-CoA
From Wikipedia, the free encyclopedia
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Acetyl-CoA 
 
 
Identifiers 
CAS number 72-89-9 
PubChem 181 
MeSH Acetyl+Coenzyme+A 
SMILES O=C(NCCSC(=O)C)CCNC(=O)[C@H](O)C(C)(C) COP(=O)(O)OP(=O)(O)OC[C@H]1O[C@H] ([C@H](O)[C@@H]1OP(=O)(O)O)n1cnc2c(N)ncnc12 
Properties 
Molecular formula C23H38N7O17P3S 
Molar mass 809.572 
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references 
Acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main use is to convey the carbon atoms within the acetyl group to Krebs Cycle to be oxidized for energy production. Chemically it is the thioester between coenzyme A (a thiol) and acetic acid (an acyl group carrier). Acetyl-CoA is produced during the second step of aerobic cellular respiration, pyruvate decarboxylation, which occurs in the matrix of the mitochondria. Acetyl-CoA then enters Krebs Cycle.

It is also an important component in the biogenic synthesis of the neurotransmitter acetylcholine. Choline, in combination with Acetyl-CoA is catalyzed by the enzyme choline acetyltransferase to produce acetylcholine and a coenzyme a byproduct.

Contents [hide]
1 Functions 
1.1 Pyruvate dehydrogenase reaction 
1.2 Fatty acid metabolism 
1.3 Other reactions 
2 See also 
3 External links 
 


[edit] Functions

[edit] Pyruvate dehydrogenase reaction
The conversion of pyruvate into acetyl-CoA is referred to as the pyruvate dehydrogenase reaction. It is catalyzed by the pyruvate dehydrogenase complex.


[edit] Fatty acid metabolism
In animals, acetyl-CoA is very central to the balance between carbohydrate metabolism and fat metabolism (see fatty acid synthesis). Normally, acetyl-CoA from fatty acid metabolism feeds into Krebs Cycle, contributing to the cell's energy supply. In the liver, when levels of circulating fatty acids are high, the production of acetyl-CoA from fat breakdown exceeds the cellular energy requirements. To make use of the energy available from the excess acetyl-CoA, ketone bodies are produced which can then circulate in the blood.

In some circumstances this can lead to the presence of ketone bodies in the blood, a condition called ketosis. Benign dietary ketosis can safely occur in people following low-carbohydrate diets, which cause fats to be metabolised as a major source of energy. This is different from ketosis brought on as a result of starvation and ketoacidosis, a dangerous condition that can affect diabetics.

In plants, de novo fatty acid synthesis occurs in the plastids. Many seeds accumulate large resevoirs of seed oils to support germination and early growth of the seedling before it is a net photosynthetic organism. Fatty acids are incorporated into membrane lipids, the major component of most membranes.


[edit] Other reactions
It is the precursor to HMG-CoA, which, in animals, is a vital component in cholesterol and ketone synthesis. Furthermore, it contributes an acetyl group to choline to produce acetylcholine, in a reaction catalysed by choline acetyltransferase. 
In plants and animals, cytosolic acetyl-CoA is synthesized by ATP citrate lyase [1]. When glucose is abundant in the blood of animals, it is converted via glycolysis in the cytosol to pyruvate, and thence to acetyl-CoA in the mitochondrion. The excess of acetyl-CoA results in production of excess citrate, which is exported into the cytosol to give rise to cytosolic acetyl-CoA. 
Acetyl-CoA can be carboxylated in the cytosol by acetyl-CoA carboxylase, giving rise to malonyl-CoA, a substrate required for synthesis of flavonones and related polyketides, for elongation of fatty acids to produce waxes, cuticle, seed oils in members of the Brassica family, and for malonation of proteins and other phytochemicals [2]. 
Two acetyl-CoA can be condensed to create acetoacetyl-CoA, the first step in the HMG-CoA/ mevalonic acid pathway leading to synthesis of isoprenoids. In plants these include sesquiterpenes, brassinosteroids (hormones), and membrane sterols. 

[edit] See also
Krebs Cycle 
HMG-CoA reductase pathway 
Fatty acid metabolism 
Acyl CoA 
Acetyl Co-A synthetase 
Malonyl-CoA decarboxylase 

[edit] External links
MeSH Acetyl+Coenzyme+A 
Retrieved from "http://en.wikipedia.org/wiki/Acetyl-CoA"
Categories: Metabolism | Molecules

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Aerobic respiration
Aerobic respiration requires oxygen in order to generate energy (ATP). It is the preferred method of pyruvate breakdown from glycolysis and requires that pyruvate enter the mitochondrion to be fully oxidized by the Krebs cycle. The product of this process is energy in the form of ATP (Adenosine Triphosphate), by substrate-level phosphorylation, NADH and FADH2.

Simplified Reaction: C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l) ΔHc -2880 kJ

The reducing potential of NADH and FADH2 is converted to more ATP through an electron transport chain with oxygen as the "terminal electron acceptor". Most of the ATP produced by aerobic cellular respiration is made by oxidative phosphorylation. This works by the energy released in the consumption of pyruvate being used to create a chemiosmotic potential by pumping protons across a membrane. This potential is then used to drive ATP synthase and produce ATP from ADP. Biology text books often say that between 36-38 ATP molecules can be made per oxidised glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 32-34 from the electron transport system). However, this maximum yield is never quite reached due to losses (leaky membranes) as well as the cost of moving pyruvate and ADP into the mitochondrial matrix.

Aerobic metabolism is more efficient than anaerobic metabolism (which yields 2 mol ATP per 1 mol glucose). They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation. The post glycolytic reactions take place in the mitochondria in eukaryotic cells, and in the cytoplasm in prokaryotic cells.
Amphiarthroses is a type of continous joint. In Amphiarthroses (slightly movable articulations), the contiguous bony surfaces are either:

symphysis: connected by broad flattened disks of fibrocartilage, of a more or less complex structure, as in the articulations between the bodies of the vertebrae. An example is the sternocostal joint. 
syndesmosis: united by an interosseous ligament, as in the inferior tibiofibular articulation. 
 The factual accuracy of part of this article is disputed.

The dispute is about Lactic acid fermentation.
Please see the relevant discussion on the talk page. 

See also: Fermentation (biochemistry) 
Anaerobic respiration(anaerobiosis) refers to the oxidation of molecules in the absence of oxygen to produce energy, in opposition to aerobic respiration which does use oxygen. Anaerobic respiration processes require another electron acceptor to replace oxygen. Anaerobic respiration is often used interchangeably with fermentation, especially when the glycolytic pathway is used for energy production in the cell. They are not synonymous terms, however, since certain anaerobic prokaryotes can generate all of their ATP using an electron transport system and ATP synthase. definition of anaerobic respiration: the breakdown of food substances in the absence of oxygen with a small amount of energy. General word and symbol equations for the anaerobic respiration of glucose can be shown as

glucose  lactic acid + energy (ATP);
C6H12O6  2C3H6O3 + 2 ATP.
The energy released is about 120 kJ per mole glucose.

Contents [hide]
1 Obligate anaerobes 
2 Facultative anaerobes and obligate aerobes 
3 Fermentation in other organisms 
4 Anaerobic respiration in prokaryotes 
5 Examples of anaerobic respiration 
6 Commercial applications of anaerobic respiration 
 


[edit] Obligate anaerobes
In some organisms called obligate (strict) anaerobes (ex: Clostridium tetani (causes tetanus), Clostridium perfringens (causes gangrene)), the presence of oxygen is lethal. This is because the presence of oxygen is processed by the organisms into the extremely toxic molecules of singlet oxygen (1O2), superoxide ion (O2-), hydrogen peroxide (H2O2), hydroxyl ion (OH-), and other toxic molecules.


[edit] Facultative anaerobes and obligate aerobes
Facultative anaerobic organisms can survive in either oxygenated or deoxygenated environments and can switch between cellular respiration or fermentation, respectively) and obligate (strict) aerobes (organisms that can survive only with oxygen) have special enzymes (superoxide dismutase and catalase) that can safely handle these products and transform them into harmless water and diatomic oxygen in the following reactions:

2O2- + 2H+ –superoxide dismutase–> H2O2 (hydrogen peroxide) + O2.
The hydrogen peroxide produced is then transferred to a second reaction:

2H2O2 –catalase–> 2H2O + O2.
The oxidative powers of the superoxide ion have now been neutralized. Only facultative anaerobes and obligate aerobes possess the two enzymes necessary to reduce the superoxide.

In organisms which use glycolysis, the absence of oxygen prevents pyruvate from being metabolised to CO2 and water via the citric acid cycle and the electron transport chain (which relies on O2) does not function. Fermentation does not yield more energy than that already obtained from glycolysis (2 ATPs) but serves to regenerate NAD+ so glycolysis can continue. Various end products can also be created, such as lactate or ethanol.

Fermentation in animals is essential to human life.

In lactic acid fermentation, the following reaction occurs:

1. Glycolysis

C6H12O6 (glucose) + 2 NAD+  2 C3H4O3 (pyruvic acid) + 2 NADH
2. Lactic acid creation

2 C3H4O3 (pyruvic acid) + 2 NADH  2 C3H6O3 (lactic acid) + 2 NAD+
Net reaction:

C6H12O6 (glucose)  2 C3H6O3 (lactic acid)




[edit] Fermentation in other organisms
In some plant cells and yeasts, fermentation produces CO2 and ethanol. The conversion of pyruvate to acetaldehyde generates CO2 and the conversion of acetaldehyde to ethanol regenerates NAD+.


[edit] Anaerobic respiration in prokaryotes
In the field of prokaryotic metabolism, anaerobic respiration has a more specific meaning. In this case, anaerobic respiration is defined as a membrane-bound biological process coupling the oxidation of electron donating substrates (e.g. sugars and other organic compounds, but also inorganic molecules like hydrogen, sulfide/sulfur, ammonia, metals or metal ions) to the reduction of suitable external electron acceptors other than molecular oxygen. In contrast, in [fFermentation (biochemistry)|fermentation]] the oxidation of molecules is coupled to the reduction of an internally-generated electron acceptor, usually pyruvate. Hence, scientists who study prokaryotic physiology view anaerobic respiration and fermentation as distinct processes and therefore do not use the terms interchangeably.

In anaerobic respiration, as the electrons from the electron donor are transported down the electron transport chain to the terminal electron acceptor, protons are translocated over the cell membrane from "inside" to "outside", establishing a concentration gradient across the membrane which temporarily stores the energy released in the chemical reactions. This potential energy is then converted into ATP by the same enzyme used during aerobic respiration, ATP synthase. Possible electron acceptors for anaerobic respiration are nitrate, nitrite, nitrous oxide, oxidised amines and nitro-compounds, fumarate, oxidised metal ions, sulfate, sulfur, sulfoxo-compounds, halogenated organic compounds, selenate, arsenate, bicarbonate or carbon dioxide (in acetogenesis and methanogenesis). All these types of anaerobic respiration are restricted to prokaryotic organisms.


[edit] Examples of anaerobic respiration
glucose + 3NO3- + 3H2O  6HCO3- + 3NH4+, ΔG0' = -1796 kJ
glucose + 3SO42- + 3H+  6HCO3- + 3SH-, ΔG0' = -453 kJ
glucose + 12S + 12H2O  6HCO3- + 12HS- + 18H+, ΔG0' = -333 kJ
All of these terminal electron acceptors are further upstream in the electron transport chain, compared to O2. Consequently, anaerobic respiration is less effective than aerobic respiration. The ΔG0' of aerobic respiration is -2844 kJ.


[edit] Commercial applications of anaerobic respiration
Anaerobic digestion 
Mechanical biological treatment 
[show]v • d • eCellular Respiration 
Aerobic Respiration Glycolysis → Pyruvate Decarboxylation → Citric Acid Cycle → Oxidative Phosphorylation (Electron Transport Chain + ATP synthase) 
Anaerobic Respiration Glycolysis → Lactic Acid Formation or Ethanol Formation 
[show]v • d • eMetabolism 
Catabolism - Anabolism 
Metabolic pathway - Metabolic network - Cellular respiration (Anaerobic/Aerobic)

Protein metabolism - Carbohydrate metabolism - Lipid metabolism - Iron metabolism 
[show]v • d • eMetabolism map 

Glucuronate metabolismPentose interconversionInositol metabolismCellulose and sucrose
metabolismStarch and glycogen
metabolismOther sugar
metabolismPentose phosphate pathwayGlycolysis and GluconeogenesisAmino sugars metabolismSmall amino acid synthesisBranched amino acid
synthesisPurine biosynthesisHistidine metabolismAromatic amino
acid synthesisPyruvate
decarboxylationAnaerobic
respirationFatty acid
metabolismUrea cycleAspartate amino acid
group synthesisPorphyrins and
corrinoids
metabolismCitric acid cycleGlutamate amino
acid group
synthesisPyrimidine biosynthesis v • d • e  All pathway labels on this image are links, simply click to access the article. 
 A high resolution labeled version of this image is available here.  
 

Retrieved from "http://en.wikipedia.org/wiki/Anaerobic_respiration"
Categories: Accuracy disputes | Anaerobic digestion | Biodegradation | Biodegradable waste management | Cellular respiration

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http://farm3.static.flickr.com/2097/1521261308_3c41ad3d93.jpg Pectoral Girdle 

 

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http://www.wiley.com/college/apcentral/anatomydrill/
Chapter 1: An Introduction to Anatomy and Physiology  
   
 Objectives 
   
 

Welcome to the Fundamentals of Anatomy & Physiology,
Seventh Edition Companion Website!   


--------------------------------------------------------------------------------

 
After successfully completing this chapter, you will be able to:

Define anatomy and physiology, and describe various specialties of each discipline. 
Identify the major levels of organization in organisms, from the simplest to the most complex.
Identify the organ systems of the human body and the major components of each system.
Explain the concept of homeostasis and its significance for organisms.
Describe how negative feedback and positive feedback are involved in homeostatic regulation.
Use anatomical terms to describe body sections, body regions,and relative positions.
Identify the major body cavities and their subdivisions. 
   




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Anatomy and Physiology 101

Class Lecture Notes are in the PDF

Quizzes on Subjects can be found here: http://lrn.org/Content/Quizzes/Quizlist.html

All of the following units are from:
http://training.seer.cancer.gov/module_anatomy/unit1_1_body_structure.html

[[Unit One]] Introduction to the Body and Functions
http://lrn.org/PDF/organization.pdf
http://lrn.org/Content/Lessons/orientation.html

[[Unit Two]]  Cells and Membranes
http://lrn.org/PDF/cells.pdf
http://lrn.org/Content/Lessons/cells.html

[[Unit Three]] The Skeletal System
http://lrn.org/PDF/skeletal.pdf
http://lrn.org/Content/Lessons/skeletal.html

[[Unit Four]] The Muscle System
http://lrn.org/PDF/muscular.pdf
http://lrn.org/Content/Lessons/muscle.html

[[Unit Five]] The Nervous System 
 http://lrn.org/PDF/nervous.pdf
http://lrn.org/Content/Lessons/nervous.html

[[Unit Six]] The Endocrine System
http://lrn.org/PDF/endocrine.pdf
http://lrn.org/Content/Lessons/endocrine.html
http://lrn.org/Content/Quizzes/Qendocrine.html
http://www.endocrineweb.com/
http://endocrinology.com/
http://www.diabetes.org/home.jsp


[[Unit Seven]] The Cardiovascular System

http://lrn.org/PDF/cardiovascular.pdf
http://lrn.org/Content/Lessons/cardio.html

[[Unit Eight]] The Lymphatic System 
http://lrn.org/PDF/lymphatic.pdf
http://lrn.org/Content/Lessons/lymphatic.html

[[Unit Nine]] The Respiratory System 
http://lrn.org/PDF/respiration.pdf
http://lrn.org/Content/Lessons/respiratory.html

[[Unit Ten]] [[The Digestive System]] 
http://lrn.org/PDF/digestive.pdf
http://lrn.org/Content/Lessons/digestive.html

[[Unit Eleven]] [[The Urinary System]]
 http://lrn.org/PDF/urinary.pdf
http://lrn.org/Content/Lessons/urinary.html

[[Unit Twelve]] The Reproductive System
 http://lrn.org/PDF/reproduction.pdf
http://lrn.org/Content/Lessons/reproductive.html

http://lrn.org/PDF/senses.pdf
http://lrn.org/Content/Lessons/senses.html


http://lrn.org/PDF/integumentary.pdf
http://lrn.org/Content/Lessons/skin.html

http://lrn.org/PDF/chemistry.pdf
http://lrn.org/Content/Lessons/chemistry.html

http://lrn.org/Content/Lessons/blood.html
http://lrn.org/PDF/blood.pdf

[[Review]]
[[Final Exam]]

[[Interesting A & P Pictures]]
ANP Study TiddlyWiki


[[3177839572]]
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5125488913763838898"><img src="http://lh4.google.com/cardwell.bob/RyFlAtUYq7I/AAAAAAAABzE/WF4zfD5qm5U/s800/autonomic.gif.jpg" /></a></html>
An axon may have infrequent branches called axon collaterals. Axons and axon collaterals terminate in many short branches or telodendria. The distal ends of the telodendria are slightly enlarged to form synaptic bulbs. Many axons are surrounded by a segmented, white, fatty substance called myelin or the myelin sheath. Myelinated fibers make up the white matter in the CNS, while cell bodies and unmyelinated fibers make the gray matter. The unmyelinated regions between the myelin segments are called the nodes of Ranvier .
 	
BIOLOGY 205  ANATOMY & PHYSIOLOGY I  EXAM 3  SPRING 2002


Please print your name here:  _______________________________

Welcome to the 3rd exam.  As always:
•	Take your time.
•	READ the entire question and all possible answer choices.  
•	THINK about the question, and eliminate those choices you know to be wrong.

 

GOOD LUCK!!!

1.	The shoulder joint could be described as:
a.	Synarthrotic but not diarthrotic
b.	Fibrous but not amphiarthrotic
	c.	Synovial and synarthrotic
	d.	Synovial and sutural
	e.	Diarthrotic but not fibrous





2.	The volume of synovial fluid would most likely be greatest in the joint between:
a.	The left parietal bone and left temporal bone
b.	The distal and middle phalanges of the left ring finger
c.	The epiphysis and diaphysis of a growing femur
d.	2 carpal bones
e.	The humerus and the scapula

3.	Which of the following is TRUE?
a.	Articular cartilage can be either hyaline or elastic cartilage
b.	Synovial fluid is formed from blood
c.	Ligaments are only found in amphiarthrotic joints
d.	Synovial joints never contain bursae
e.	None of the above

4.	The atloaxial joint is an example of a:
a.	Condyloid joint
b.	Hinge joint
c.	Pivot joint
d.	Synarthrotic joint
e.	Petrous joint

5.	Rheumatoid arthritis is an example of a(n):
a.	Acquired immunodeficiency disease
b.	Arthritic condition primarily involving the body’s red blood cells
c.	Disorder involving a decreased rate of uric acid synthesis
d.	Disorder involving greater than normal antibody activity
e.	Disorder involving a moderate increase in the synthesis of synovial contractile epithelium

6.	Which of the following is NOT considered part of the knee?
a.	Patellofemoral joint 
b.	Medial patellotibial joint
c.	Medial tibiofemoral joint
d.	Medial femorofibular joint
e.	2 of the above

7.	The anterior cruciate ligament prevents:
a.	Hyperextension of the knee 
b.	Hyperflexion of the knee
c.	Lateral rotation of the knee
d.	Medial rotation of the knee
e.	Lateral extension of the knee

8.	The joint between the frontal bone and the parietal bones could be described as:
a.	Amphiarthrotic
b.	Cartilaginous
c.	Fibrous
d.	Diarthrotic
e.	Synovial

9.	Arrange the following in order from SMALLEST to LARGEST.
1.	Muscle Organ
2.	Myofibril
3.	Myofilament
4.	Fascicle
5.	Muscle Cell

a.	1, 4, 3, 5, 2
b.	3, 2, 5, 4, 1
c.	2, 3, 5, 4, 1
d.	3, 2, 4, 5, 1
e.	2, 3, 4, 5, 1

10.	Which of the following is NOT a function of muscle tissue?
a.	Maintenance of posture
b.	Joint stabilization
c.	Pumping blood
d.	Thermogenesis
e.	None of the above

11.	Which of the following would you expect to find more than one of within a skeletal muscle fiber?
I.	Nuclei
II.	Mitochondria
III.	Myofibrils
IV.	Terminal Cisternae

a.	I and III
b.	III
c.	I, II, and III
d.	III and IV
e.	I, II, III, and IV




12.	Which of the following must Ca2+ bind to in order for contraction to proceed?
a.	Calsequestrin
b.	Tropomyosin
c.	Troponin
d.	Actin
e.	Myosin

13.	As a sarcomere contracts, the length of the I band will:
a.	Always increase
b.	Sometimes increase
c.	Always decrease
d.	Sometimes decrease
e.	Always stay the same

14.	Which of the following is CORRECT?  
a.	Fascicle size <  Fiber size
b.	Number of sarcomeres in a muscle fiber > Number of A bands in a             		muscle fiber
c.	Length of the H zone < Length of the A band
d.	Distance between 2 Z discs >  the length of an A band plus the 			length of an I Band
e.	All of the above

15.	Which of the following is NOT involved in the generation of the membrane potential in a skeletal muscle cell?
a.	The sodium-potassium pump
b.	Leakage of potassium out of the cell
c.	Presence of protein anions within the cell
d.	Leakage of Cl- into the cell
e.	3 of the above are NOT involved

16.	Nicotine binds to acetylcholine receptors on the sarcolemma and causes skeletal muscle contraction.  Based on this fact, which of the following is most likely?
a.	Nicotine causes the cell membrane potential to become more negative
b.	Nicotine causes potassium to enter the cell
c.	Nicotine causes the sarcolemma to fragment which allows sodium 			to enter
d.	Nicotine causes depolarization of the cell and initiates an action   			potential
e.	Both A and B are likely 

17.	Direct injection of calcium into a skeletal muscle fiber will result in:
a.	Muscle relaxation
b.	Muscle contraction
c.	Nothing
d.	A massive increase in intracellular pH
e.	Rapid repolarization

18.	Which of the following would you expect to cover the largest surface area?
a.	A single perimysium from the brachioradialis
b.	A single endomysium from the brachioradialis
c.	A single epimysium from the brachioradialis
d.	A single sarcoplasmic reticulum from the brachioradialis
e.	A single sarcolemma from the brachioradialis

19.	Which of the following does NOT belong?
a.	Epimysium
b.	Aponeurosis
c.	Tendon
d.	Dense regular connective tissue
e.	Ligament

20.	The chemical Tetraethylammonium (TEA) stops voltage-gated potassium channels from functioning.  Thus, you expect TEA to prevent:
a.	Skeletal muscle cell depolarization
b.	Skeletal muscle cell contraction
c.	Skeletal muscle cell repolarization
d.	All of the above 
e.	None of the above

21.	The venom of a puffer fish (tetrodotoxin) stops voltage-gated sodium channels from functioning.  Thus, you would expect a skeletal muscle cell treated with tetrodotoxin to:
a.	Produce stronger than normal action potentials
b.	Produce action potentials quicker
c.	To be unable to produce action potentials
d.	To be able to depolarize but not repolarize
e.	Both A and B are correct






22.	Which of the following terms accurately describes a typical skeletal muscle fiber?
a.	Extremely short
b.	Branched
c.	Uninucleate
d.	Involuntary 
e.	None of the above

23.	Arrange the following in the order in which they would occur in a skeletal muscle cell.
1.	Uptake of a fatty acid from the blood stream
2.	Electron transport chain
3.	Krebs cycle
4.	Chemical reaction producing molecules of acetyl CoA
5.	Reduction of O2 to yield H2O

a.	1, 5, 4, 3, 2
b.	4, 1, 3, 2, 5
c.	1, 3, 4, 2, 5
d.	1, 4, 3, 5, 2
e.	1, 4, 3, 2, 5

24.	The drug physostigmine inhibits the enzyme acetylcholinesterase.  Thus, you would expect injection of this drug to cause skeletal muscle contraction to:
a.	Decrease in strength
b.	Increase in duration
c.	Decrease in duration
d.	Not occur at all
e.	Both A and C are correct

25.	Which of the following occurs within a muscle cell?
a.	Energy creation via ATP synthesis
b.	Conversion of chemical energy to mechanical energy
c.	Utilization of carbon dioxide
d.	Production of oxygen
e.	None of the above






26.	If you inhibited the enzyme creatine kinase, you would expect the muscle cell to be:
a.	Able to produce more ATP
b.	Able to produce less ATP 
c.	Unable to produce any ATP
d.	Totally unable to contract
e.	None of the above

27.	Which of the following is NOT a byproduct of any of the ATP generating reactions that occur within a skeletal muscle cell?
a.	CO2
b.	H2O
c.	Lactic Acid
d.	Heat
e.	O2

28.	Which of the following is TRUE concerning aerobic metabolism in a skeletal muscle cell?
a.	It is less efficient than anaerobic metabolism
b.	It does not require oxygen in order to proceed
c.	Portions of the process occur within the mitochondria
d.	It requires carbon dioxide in order to proceed
e.	It results in the production of approximately 6.02 x 1023 molecules of ATP

29.	A somatic motor neuron and all the muscle fibers it innervates is the definition of a(n):
a.	Motor unit
b.	Motor pool
c.	Motor end plate
d.	Neuromuscular junction
e.	Aponeurosis

30.	As resistance increases, the speed of muscle contraction will:
a.	Increase
b.	Decrease
c.	Stay the same








31.	Consider the following hypothetical graph of tension developed vs. time in an isolated skeletal muscle fiber.  



      Tension
      (grams)



		 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
				Time (seconds) 
		
		Which of the following is correct?

a.	The fiber was stimulated at 1, 5, and 8 seconds and this represents unfused tetanus
b.	The fiber was stimulated at 1 and 5 seconds and this represents treppe
c.	The fiber was stimulated at 1, 5, and 8 seconds and this represents temporal summation
d.	The fiber was stimulated at 1, 5, and 8 seconds and this represents tetanus
e.	The fiber was stimulated at 1, 5, and 8 seconds and this represents isokinetic contractions


32.	Which of the following most likely represents the change in tension developed during an isotonic contraction of a skeletal muscle?  Assume the x-axis to be time and the y-axis to be muscle tension.

Correct











33.	White skeletal muscle fibers contain lots of mitochondria and are predominantly used for endurance type activities.
a.	This statement is TRUE
b.	This statement is FALSE

34.	A certain disease results in a decreased number of functioning acetylcholine receptors on skeletal muscle fibers.  Which of the following might be the best treatment?
a.	Eserine, an inhibitor of acetylcholinesterase
b.	Botulinum toxin, which prevents exocytosis of acetylcholine
c.	2,4-dinitrophenol, an inhibitor of ATP synthesis
d.	Ouabain, an inhibitor of the sodium-potassium pump
e.	Hexamethonium, a chemical that prevents acetylcholine from binding to its receptors



 

35.	Here’s a picture of a young Arnold Schwarzenegger.  His massively developed biceps brachii are a result of:
a.	Muscle cell hyperplasia
b.	Muscle cell atrophy
c.	Muscle cell hypertrophy
d.	Muscle cell dystrophy
e.	Muscle cell anaplasia

36.	Smooth muscle is NOT:
a.	Involuntary
b.	Controlled by the autonomic nervous system
c.	Non-striated
d.	Found in the urinary OR respiratory system
e.	Multinucleate 



37.	Consider the following events in the stimulation of a muscle fiber and arrange them in chronological order.
1.	Exocytosis of acetylcholine by synaptic end bulb
2.	Arrival of an action potential at the telodendria
3.	Opening of fast sodium channels in the sarcolemma
4.	Opening of calcium channels in the sarcoplasmic reticulum

a.	1, 2, 3, 4
b.	2, 1, 4, 3
c.	1, 2, 4, 3
d.	2, 1, 3, 4
e.	None of the above

38.	Verapimil is a drug that reduces calcium entry into smooth muscle cells.  Intravenous infusion of verapimil would cause the tone (level of contraction) of arterial smooth muscle to:
a.	Increase
b.	Decrease
c.	Stay the same

39.	Which of the following are found in BOTH skeletal and smooth muscle fibers?
a.	Dense bodies
b.	Z discs
c.	Sarcomeres
d.	Mitochondria
e.	A bands

40.	Your 1st assignment in your new job as the main histologist at the U.S. Department of Tissue Analysis (USDTA) is to analyze a sample of smooth muscle.  In your microscopic examination, you notice a significant number of gap junctions.  You thus conclude that the sample:
a.	Cannot be smooth muscle
b.	Is an example of multi-unit smooth muscle
c.	Could be fetal smooth muscle but not adult smooth muscle
d.	Is an example of single-unit smooth muscle
e.	Must have been under the control of the somatic nervous system







41.	In your 2nd histological assignment, you analyze a tissue sample and notice that the cells of interest contain:
•	Striations
•	Absence of myosin light chain kinase
•	Desmosomes
•	Mitochondria
•	Glycogen 
•	No more than 1 or occasionally 2 nuclei

a.	This tissue is skeletal muscle 
b.	This tissue is cardiac muscle
c.	This tissue is smooth muscle
d.	This tissue could not be cardiac, smooth, or skeletal muscle
e.	It cannot be determined whether this skeletal or cardiac muscle

42.	Duchenne muscular dystrophy is:
a.	A relatively harmless disorder
b.	A disorder characterized by excessive skeletal muscle growth
c.	A disorder more common in boys than in girls
d.	Both A and C are correct
e.	None of the above

43.	Compared to lifting a puppy that weighs 2lbs, lifting a rhesus monkey that weighs 100lbs will require:
a.	The contraction of more sarcomeres per myofibril
b.	The contraction of more myofibrils per muscle fiber
c.	The contraction of more muscle fibers per muscle organ
d.	Both A and B
e.	A, B, and C

44.	The hind leg muscles of a kangaroo are designed for hopping at speeds of up to 40mph for very, very brief periods of time.  Based on this you would expect those skeletal muscles to have fibers that are:
a.	White and aerobic
b.	White and anaerobic
c.	Red and aerobic
d.	Red and anaerobic
e.	Red and lacking mitochondria





For questions 45 – 50, use the following answer choices.  Each choice may be used once, more than once, or not at all.
a.	Actin
b.	Myosin
c.	Troponin
d.	Tropomyosin
e.	Tubulin

45.	Binds calcium  C

46.	In a relaxed muscle, it blocks the myosin binding sites on actin  D

47.	Attached to the Z discs  A

48.	Makes up the bulk of the thin filament  A

49.	Found in the H zone  B

50.	Performs the “power stroke”  B

For questions 51 – 60, use the following answer choices.  Each choice may be used once, more than once, or not at all.
a.	Skeletal Muscle
b.	Cardiac Muscle
c.	Smooth Muscle
d.	Both A and B
e.	A, B, and C

51.	Contains striations  D

52.	Under voluntary control  A

53.	Can contract or relax upon stimulation  C

54.	Forms sphincters  C

55.	Can be multi-unit or single unit  C

56.	Formed via the fusion of embryonic cells known as myoblasts  A

57.	Depends on a source of oxygen  E

58.	Responsible for movement of fluids  (THINK ABOUT THIS ONE!)  E

59.	Fibers can be up to 300 millimeters long  A

60.	Contains intercalated discs  B



61.	Ethylenediaminetetra-acetic acid (EDTA) is a chemical that has a very high affinity for calcium ions.  Suppose you injected some EDTA into a skeletal muscle fiber, and then stimulated the muscle fiber.  You would expect any resulting contraction of that fiber to be:
a.	Normal
b.	Stronger than normal
c.	Weaker than normal

62.	Which of the following is NOT a characteristic of muscle tissue?
a.	Extensibility
b.	Contractility
c.	Excitability
d.	Elasticity
e.	None of the above

63.	Which of the following would you NOT expect to find within a muscle organ?
a.	Blood vessels
b.	Connective tissue
c.	Nervous tissue
d.	Lymphatic vessels
e.	Cartilage

64.	A prolonged spasm that causes a muscle to become taut and painful is a(n):
a.	Example of flaccid paralysis
b.	Twitch
c.	Cramp
d.	Example of plasmolysis
e.	Contraction 
BIOLOGY 205 – ANATOMY AND PHYSIOLOGY 	NAME:_____KEY________
EXAM 1 – SPRING 2002 – FORM A
IMHOLTZ

INSTRUCTIONS:
•	THERE ARE MULTIPLE FORMS OF THIS EXAM.  THIS IS FORM A.  PLEASE WRITE “FORM A” ON YOUR SCANTRON.  IF YOU DO NOT DO THIS, YOUR EXAM WILL NOT BE GRADED! 
•	THERE ARE 64 QUESTIONS.  EACH QUESTION HAS ONLY ONE CORRECT ANSWER.  CHOOSE THE ONE YOU BELIEVE TO BE BEST.  FILL IN THE CORRESPONDING CHOICE ON YOUR SCANTRON.
•	EACH QUESTION IS WORTH 2 POINTS.
•	READ EACH QUESTION FULLY AND CAREFULLY.  TAKE YOUR TIME AND THINK.
•	GOOD LUCK!

 

1.	Which of the following pairings is CORRECT?
a.	Histology -  strictly refers to the analysis of tissues as seen by the naked eye
b.	Pathology - can involve the study of situations in which the body has failed to maintain homeostasis
c.	Embryology - study restricted to analysis of zygote formation
d.	Physiology - discipline which is intimately tied to anatomy but has NO relationship to cytology
e.	All of the above are correct

2.	Which of the following pairs contain organs found in both systems?
a.	Cardiovascular - Endocrine
b.	Digestive - Endocrine
c.	Integumentary - Digestive
d.	2 of the above 
e.	All of the above


3.	In a negative feedback loop, the response to the original stimulus causes the amplitude of that stimulus to:
a.	Increase
b.	Decrease 
c.	Stay the same

4.	Which of the following is TRUE?
a.	The number of negative feedback systems in the body is much less than the number of positive feedback systems in the body
b.	Positive feedback is ALWAYS detrimental to one's health
c.	Maintenance of blood glucose concentration at homeostatic levels (90mg/100ml) is an example of a negative feedback loop.
d.	Positive feedback is NEVER detrimental to one's health
e.	A and C are both TRUE

5.	Homeostasis can be considered:
a.	The maintenance of a dynamically stable internal environment
b.	The maintenance of a static yet stable internal environment
c.	A process that is maintained only by the activities of the digestive system
d.	An internal environment that changes as the external environment changes
e.	A situation where the degree of internal change is proportional to the square of the degree of external change

6.	Which of the following are examples of extracellular fluid?
I.	Lymph
II.	Blood
III.	Cerebrospinal fluid
IV.	Intraocular fluid

a.	I,II, and III only
b.	I, II, and IV only
c.	I and II only
d.	I,II, III, and IV
e.	II, III, and IV only

7.	Which of the following is an example of NEITHER muscle nor connective tissue?
a.	Bone
b.	Cardiac muscle within the atrium of the heart
c.	Blood
d.	Hyaline cartilage
e.	None of the above


8.	Consider the following statement:
All epithelia that serve a protective function must contain goblet cells, since the mucus secreted by goblet cells helps prevent pathogens from entering the body.

a.	This statement is TRUE
b.	This statement is FALSE

9.	In which of the following might you expect to find all of the following:
1.	Nonkeratinized stratified squamous epithelium
2.	Simple columnar epithelium
3.	Simple columnar epithelium with goblet cells
4.	Simple columnar epithelium with microvilli
5.	NO pseudostratified columnar epithelium

a.	Glomerular capsule
b.	Digestive Tract
c.	Respiratory tract
d.	Sebaceous gland duct
e.	Exterior body surface

10.	What is the main function of keratinized stratified squamous epithelium?
a.	Protection and absorption of nutrients
b.	Protection 
c.	Absorption of nutrients 
d.	Protection and endocrine secretion
e.	Endocrine secretion 

11.	Endocrine and exocrine glands:
a.	Are both predominantly composed of connective tissue
b.	Are both glands that secrete substances into ducts
c.	Are both glands that secrete substances into the bloodstream 
d.	Are both always unicellular
e.	None of the above

12.	A compound alveolar exocrine gland:
a.	Has a duct which does not branch
b.	Has a secretory portion that is tubular
c.	Secretes hormones
d.	Must be a multicellular gland
e.	Is the correct classification for the thyroid gland





13.	Which of the following is NOT TRUE of epithelia?
a.	Epithelial cells typically exhibit polarity
b.	Epithelia are always supported by a layer of connective tissue
c.	Epithelia has the ability to regenerate only when it contains a sufficient amount of blood vessels
d.	Epithelia are classified based on the number of cell layers and on the shape of the cells in the apical layer
e.	Epithelial cells are often strongly connected to adjacent cells via tight junctions and/or desmosomes

14.	Why is it beneficial that the alveoli of the lungs consist of simple squamous epithelium?
a.	It decreases the rate of gas exchange
b.	It decreases the distance of diffusion for O2 while at the same time increasing the distance of diffusion for CO2
c.	It facilitates gas exchange in the lungs by decreasing the distance of diffusion for ALL gases involved
d.	It increases the ability of the lungs to undergo thermogenesis
e.	All of the above

15.	Which of the following does NOT belong?
a.	Simple squamous epithelium
b.	Small Intestine
c.	Microvilli
d.	Goblet cells
e.	Nutrient absorption

16.	In situation X, we have the amount of keratin found in a 2cm2 area of the stratified squamous epithelium of the ventral surface of the hand.
In situation Y, we have the amount of keratin found in a 2cm2 area of the stratified squamous epithelium of the lining of the oral cavity.

a.	Amount in situation X is far greater than the amount in situation Y
b.	Amount in situation X far less than the amount in situation Y
c.	Amount in situation X is approximately equal to the amount in situation Y
d.	Both A and B could be correct.  It depends on the sex of the individual.
e.	It cannot be determined which of the above answers is correct since we are not taking into account individual variation.





17.	Which of the following epithelia types undergoes drastic alterations of its morphology in response to stretch?
a.	Transitional epithelium
b.	Stratified cuboidal epithelium
c.	Stratified columnar epithelium
d.	Simple squamous epithelium
e.	Both B and C are correct

18.	Which of the following are functions of connective tissue?
I.	Support
II.	Physical protection
III.	Storage
IV.	Heat production

a.	I and III only
b.	I, II, and III only
c.	I and II only
d.	II and III only
e.	I, II, III, and IV

19.	Fibrous connective tissue (a.k.a. connective tissue proper) contains:
a.	Cells
b.	Fibers
c.	Ground substance
d.	All of the above
e.	None of the above

20.	Fibroblasts may be found in:
a.	Areolar connective tissue
b.	Loose connective tissue
c.	Dense regular connective tissue
d.	Dense irregular connective tissue
e.	All of the above












21.	Which of the following types of connective tissue exhibits these characteristics:
1.	Copious amount of blood vessels
2.	Dominated by large empty looking cells with thin margins and considerable amounts of stored lipids
3.	Often pale
4.	Performs cushioning functions for the kidneys and the posterior portions of the eyes.

a.	Areolar
b.	Dense regular connective tissue
c.	Dense irregular connective tissue
d.	Adipose tissue
e.	Reticular tissue

22.	The main function of dense regular connective tissue is:
a.	To resist stresses that are applied in all directions
b.	To resist those stresses that are applied in the same direction as the collagenous fibers within the tissue
c.	To attach epithelia to underlying organs
d.	Energy storage
e.	Energy creation

23.	Bone typically heals faster than cartilage because:
a.	Cartilage is highly vascular while bone is not
b.	Bone is highly vascular while cartilage is not
c.	Cartilage has a low H2O content
d.	Chondroblasts are actually dead cells
e.	Cartilage has a flexible, rubbery matrix while bone does not

24.	Hyaline cartilage:
a.	Forms the majority of the fetal skeleton
b.	Attaches the ribs to the sternum
c.	Forms supportive rings around the trachea which helps keep the airway patent
d.	All of above are correct
e.	Only 2 of the above are correct

25.	The external ear and the _____________ both contain ____________.
a.	Epiglottis:	Fibrocartilage
b.	Eustachian tube:	Elastic cartilage
c.	Epidermal papillae:	Elastic cartilage
d.	Glomerular membrane:	Dense regular connective tissue
e.	None of the above


26.	Fibrocartilage:
I.	Has very little extracellular matrix
II.	Can be found in the intervertebral disks
III.	Is found within the epidermis
IV.	Resists compression in certain joints

a.	II and IV are correct
b.	II and III are correct
c.	II and IV are correct
d.	I and IV are correct
e.	I and III are correct

27.	Glial cells are characteristic of:
a.	Muscle tissue
b.	Loose connective tissue
c.	Dense connective tissue
d.	Epithelial tissue
e.	Nervous tissue

28.	A stab wound that resulted in lung collapse most likely involved penetration of a:
a.	Pericardial membrane
b.	Pleural membrane
c.	Synovial membrane
d.	Cutaneous membrane ONLY
e.	Peritoneal membrane

29.	Which of the following is TRUE of mucous membranes?
a.	They always contain mucus-secreting cells
b.	They are not found in the reproductive tract
c.	Usually contain an epithelial layer, and a connective tissue layer known as the muscularis mucosae
d.	Often have absorptive, secretory, and protective functions
e.	They never contain goblet cells

30.	A type of membrane that lines a cavity which does not open to the exterior of the body is:
a.	Synovial membrane
b.	Serous membrane
c.	Pericardial membrane
d.	Pleural membrane
e.	All of the above




31.	______________ prevent fluids from seeping between epithelial cells.
a.	Desmosomes
b.	Hemi-desmosomes
c.	Glycosaminoglycans
d.	Colloid 
e.	Tight junctions

32.	The replacement of damaged tissue with scar tissue is known as:
a.	Fibrosis
b.	Regeneration
c.	Exfoliation
d.	Involution
e.	Invagination

33.	Which of the following is the greatest?
a.	Surface area covered by all the synovial membranes in the body
b.	Surface area covered by the pleural membranes
c.	Surface area covered by the pericardial membrane
d.	Surface area covered by peritoneal membrane
e.	Surface area covered by the cutaneous membranes

34.	In pseudostratified epithelium,
a.	All the cells border the lumen
b.	All the cells touch the basement membrane
c.	All the cells are squamous
d.	All the cellular nuclei are immediately adjacent to the basement membrane
e.	Cilia are never found on the apical-most cells

35.	The only example of holocrine secretion in the entire body is exhibited by:
a.	Apocrine sweat glands
b.	Holocrine sweat glands
c.	Mammary glands
d.	Endocrine glands
e.	Sebaceous glands

36.	Which of the following connective tissue types is INCORRECTLY matched with its locations?
a.	Reticular tissue:	Spleen, Lymph Nodes
b.	Adipose tissue:	Cushioning behind eyes, Hypodermis
c.	Dense Regular:	Ligaments, Tendons
d.	Hyaline cartilage:	Fetal skeleton, External ear, Epiglottis
e.	Dense Irregular:	Reticular dermis, Perichondrium



37.	Smoking causes the function of respiratory __________ to ___________.
a.	Microvilli;	Increase
b.	Microvilli;	Decrease
c.	Cilia;		Increase
d.	Cilia;		Decrease
e.	None of the above

38.	You look at some epithelial tissue under the microscope and notice its cells have a stratified cuboidal appearance.
a.	These cells could be involved in the secretion of female sex hormones
b.	These cells could be surrounding developing eggs within the ovary
c.	These cells could be found on the surface of the oral cavity
d.	All of the above are correct
e.	None of the above are correct

39.	Individuals with Marfan's syndrome cannot make a protein called fibrillin.  This protein is a significant component of elastic fibers.  Which of the following might individuals with Marfan's syndrome suffer from?
a.	Abnormally weak tendons
b.	Abnormally structured hyaline cartilage
c.	Abnormally weak ligaments
d.	Inability to store lipids 
e.	Arteries that are unable to spring back after they've been stretched 

40.	Which of the following body systems are involved in excretion of cellular wastes?
I.	Respiratory system
II.	Digestive system
III.	Urinary system

a.	I ONLY
b.	I and II ONLY
c.	I and III ONLY
d.	II and III ONLY
e.	I, II, and III

41.	Early in his career, the famous basketball player, Larry Bird, suffered a torn medial collateral ligament in his knee.  The type of tissue injured could be best classified as:
a.	Highly vascular
b.	Dense irregular connective tissue
c.	Areolar connective tissue
d.	Dense regular connective tissue
e.	Dense reticular connective tissue


 

42.	Consider the cartoon above.  If the boy succeeds in sawing the girl into an equal sized bottom and top half, he will have probably cut through which of the following:
I.	Epithelial Tissue
II.	Areolar Connective Tissue
III.	Adipose Tissue
IV.	Cutaneous Membrane

a.	I, II, and IV
b.	I, III, and IV
c.	I and IV
d.	I, II, III, and IV

43.	If the epithelium lining the intestine lacked microvilli, the amount of nutrients that could be absorbed would:
a.	Increase
b.	Decrease
c.	Not change

44.	Here’s a question about negative feedback.  Aldosterone is a hormone that causes blood pressure to increase.  In someone with low blood pressure, you would expect the level of aldosterone in the blood to be:
a.	Greater than normal
b.	Less than normal
c.	Normal

45.	Consider the following statement:
Damage to the kidneys will have no effect on the cardiovascular system since the kidneys belong to the urinary system and do not belong to the cardiovascular system.

a.	This statement is TRUE
b.	This statement is FALSE

46.	Which of the following is correctly arranged from LARGEST to SMALLEST?
a.	Organ – Cell – Tissue
b.	Organ System – Macromolecule – Cell 
c.	Organ – Macromolecule – Atom 
d.	Tissue – Organ – Organ System
e.	None of the above
47.	Cancer is abnormal, uncontrolled cell division.  What property of epithelial might (and does) make them more prone to develop cancer?
a.	Epithelia contain a lot of extracellular matrix
b.	Epithelia are quite vascular
c.	Epithelial cells can be squamous, cuboidal, or columnar
d.	Epithelial cells have a high capacity for regeneration
e.	Epithelia can be arranged in sheets 

48.	A cell of the intestinal epithelium secretes a substance into the extracellular space, where it is picked up by the blood and carried to the pancreas.  In this situation, this intestinal epithelial cell is most likely a(n):
a.	Exocrine cell
b.	Endocrine cell
c.	Squamous cell
d.	Keratinized cell
e.	A and C are both correct

49.	Which of the following is NOT a specialized type of cell found in connective tissue?
a.	Leukocyte
b.	Macrophage
c.	Goblet cell
d.	Mast cell
e.	Fibroblast 

50.	Which of the following tissues is/are important in body immunity?
a.	Blood
b.	Reticular tissue
c.	Dense regular connective tissue
d.	All of the above are important
e.	2 of the above are important

51.	Endothelium and mesothelium are both examples of ___________ epithelium.
a.	Simple cuboidal
b.	Simple columnar
c.	Simple squamous
d.	Stratified squamous
e.	Transitional 





52.	The diaphragm is the muscular sheet separating the thoracic and abdominal cavities.  It is lined by the ________ and _________ membranes.
a.	Parietal pleura:  visceral peritoneum
b.	Visceral pericardium: parietal peritoneum
c.	Spinal:  abdominopelvic
d.	Thoracic: abdominal
e.	Parietal pleura:  Parietal peritoneum

53.	Which of the following tissues pumps blood?
a.	Muscle
b.	Nervous
c.	Epithelial
d.	Connective
e.	None of the above

54.	A tissue is defined as a group of similarly specialized cells which together perform many generalized functions.
a.	This statement is TRUE
b.	This statement is FALSE

55.	 Which of the following graphs most likely represents the negative feedback regulation of blood calcium?
 





56.	In a minor skin wound, you would expect the damaged epithelium to ____________ and the damaged connective tissue to ___________.
a.	Undergo fibrosis:		Undergo fibrosis
b.	Undergo apoptosis:		Undergo regeneration
c.	Undergo regeneration:	Undergo regeneration
d.	Undergo regeneration:	Undergo fibrosis	
e.	None of the above

57.	Which of the following probably contains the most ground substance?
a.	Dense irregular connective tissue
b.	Dense elastic tissue
c.	Dense regular connective tissue
d.	Areolar connective tissue
e.	Transitional epithelium

58.	Which of the following is NOT a typical function of epithelial tissue?
a.	Absorption
b.	Secretion of hormones
c.	Secretion of mucus
d.	Filtration
e.	Contraction 

59.	Memory, decision making, and issuing commands are functions of _______ tissue.
a.	Connective
b.	Immune
c.	Muscle
d.	Nervous
e.	Epithelial

60.	The secretion of oil, tears, and milk are functions of _________ tissues.
a.	Loose connective 
b.	Dense connective
c.	Epithelial
d.	Nervous
e.	Muscle

61.	Which organ system helps maintain the volume and composition of the body fluids that bathe the body cells?
a.	Urinary
b.	Endocrine
c.	Digestive
d.	Immune
e.	Cardiovascular

62.	Which organ system uses chemical messengers to control and guide body functions?
a.	Nervous
b.	Endocrine
c.	Cardiovascular
d.	Respiratory
e.	Integumentary

63.	Which connective tissue type forms protective capsules around organs?
a.	Dense regular
b.	Dense irregular
c.	Adipose
d.	Simple cuboidal
e.	Reticular 

64.	Which of the following terms describes the portion of an epithelial cell that is closest to a free surface?
a.	Basal
b.	Basolateral
c.	Lateral
d.	Apical
e.	Proximal
BIOLOGY 205:  ANATOMY AND PHYSIOLOGY I
EXAM II – SPRING 2002


NAME ______________________________________

CIRCLE YOUR LAB TIME:   TUES/THURS 800AM	TUES/THURS 1230PM	         WED/FRI 930AM

INSTRUCTIONS AND KEY INFORMATION:
•	PLEASE READ THE ENTIRE QUESTION AND ALL ANSWER CHOICES.
•	NOTE IMPORTANT QUALIFYING WORDS SUCH AS: NEITHER, NEVER, MUST, CANNOT, ETC.
•	THINK! TAKE YOUR TIME.  ELIMINATE THE ANSWERS THAT YOU KNOW ARE WRONG.
•	AS ALWAYS, CHOOSE THE BEST ANSWER!
•	GOOD LUCK!

 

1.	The upper layer of the dermis is the ____________ and is made primarily of  ___________.
a.	Epidermis;		stratified squamous keratinized epithelium
b.	Reticular dermis;	areolar connective tissue
c.	Papillary dermis;	areolar connective tissue
d.	Reticular dermis;	dense irregular connective tissue
e.	Papillary dermis;	dense regular connective tissue


2.	As you go from the stratum spinosum to the stratum lucidum, the amount of keratin per cell will:
a.	Increase
b.	Decrease
c.	Stay the same

3.	Which of the following associations is INCORRECT?
a.	Keratinocytes:	found in the stratum spinosum
b.	Langerhans cells:	immune cells
c.	Melanocytes:		typically found in the stratum corneum
d.	Merkel cells:		sensory cells
e.	Adipocytes:		fat cells

4.	Which of the following would be the thickest in a sample of epidermis from the sole of the foot?
a.	Stratum basale
b.	Stratum germinativum
c.	Stratum lucidum
d.	Stratum spinosum
e.	Stratum actinidum

5.	The oxygen consumption of cells in the stratum basale is ________ the oxygen consumption of cells in the stratum lucidum.
a.	Typically greater than
b.	Never greater than
c.	Always less than
d.	Always the same as
e.	This question cannot be answered with the information provided

6.	The stratum corneum:
a.	Is the layer of the epidermis that contains the youngest cells
b.	Provides no protection from mechanical abrasion
c.	Is the thinnest cell layer in thin skin
d.	Can be considered an example of epithelial connective tissue
e.	None of the above

7.	Which of the following describes the pigment(s) MADE in the skin?
a.	Hemoglobin and carotene
b.	The complex carbohydrate, melanin
c.	A protein lacked by albinos
d.	A protein whose synthesis is dependent on a complete absence of ultraviolet radiation
e.	Melanin, carotene, and hemoglobin

8.	Which of the following skin color abnormalities would be least worrisome if presented by an otherwise healthy individual?
a.	Jaundice
b.	Cyanosis
c.	Erythema
d.	Both B and C
e.	Both A and B

9.	The majority of the appendages of the skin are located within the
a.	Epidermis
b.	Dermis
c.	Hyperdermis
d.	Superficial fascia
e.	Subcutaneous layer

10.	Compared to pure water, the pH of sweat is more __________.  This gives it ________ properties.
a.	Basic:		bacteriostatic
b.	Basic:		bactericidal
c.	Acidic:		bactericidal
d.	Acidic:		basic
e.	Neutral:	bacteriostatic

11.	As sebum secretion increases, the skin’s permeability to water will:
a.	Increase
b.	Decrease
c.	Not change

12.	The cells of the hair shaft have a greater demand for oxygen than do the cells of the hair follicle.
a.	This statement is TRUE
b.	This statement is FALSE

13.	Which of the following structures are often associated with hair follicles?
I.	Sebaceous glands
II.	Apocrine sweat glands
III.	Eccrine sweat glands
IV.	Merocrine sweat glands
V.	Arrector pili
VI.	Hair root plexus

a.	I, II, III, and V
b.	I, V, and VI
c.	I, II, V, and VI
d.	I, II, and VI
e.	I, II, III, IV, V, IV

14.	Which of the following associations is INCORRECT?
a.	Nail matrix:			Production of new nail cells
b.	Hyponychium:		Cuticle
c.	Nail:				Scale-like modification of the epidermis on the 
dorsal surface of the distal portion of fingers 
d.	Lunula:			Half-moon at the base of the nail plate
	e.	High capillary density:	Pinkish hue of the nail bed
15.	Subcutaneous tissue:
a.	Is also known as the deep fascia
b.	Has an equal distribution between the sexes
c.	Anchors the skin to underlying muscles
d.	Is also known as the hyperdermis
e.	Contains very little adipose tissue

16.	The most dangerous type of skin cancer discussed in class:
a.	Is also the most common type of skin cancer
b.	Arises from keratinocytes of the stratum spinosum
c.	Is NOT an example of uncontrolled cell growth
d.	Often arises from a pre-existing mole
e.	Primarily involves the cells that are also known as epidermal dendritic cells

17.	Cells capable of undergoing mitosis are found in which layer(s) of the epidermis?
a.	Stratum Basale ONLY
b.	Strata Basale and Spinosum
c.	Strata Basale, Spinosum, and Granulosum
d.	Strata Germinativum and Granulosum
e.	Stratum Corneum ONLY

18.	You pick up a piece of wood and a splinter pierces the top 3 layers of skin on the palm of your hand.  Of the following layers, which were pierced?
a.	Stratum Granulosum
b.	Stratum Spinosum
c.	Stratum Germinativum
d.	Stratum Osteum
e.	All of the above

19.	The elderly are more likely to become sunburned because….
a.	They have decreased Vitamin D production
b.	They have a decrease rate of hemoglobin synthesis
c.	They have a decreased number of active Langerhans cells in the dermis
d.	They have decreased melanocyte activity
e.	They have increased amount of keratin in the stratum basale

20.	Which of the following is NOT a function of subcutaneous tissue?
a.	Energy creation
b.	Thermal insulation
c.	Shock absorption
d.	Both A and B
e.	Both B and C


21.	Crack cocaine owes its potency to the fact that it is less hydrophilic than regular cocaine.  As a result…
a.	Regular cocaine can diffuse through the plasma membrane faster than crack cocaine.
b.	Crack cocaine is more soluble in water
c.	Crack cocaine has a greater need for a protein transporter to facilitate its passage through the cell membrane
d.	Regular cocaine is less soluble in the interior of the phospholipid bilayer
e.	All of the above

22.	The use of an oxygen mask would cause a(n) _________ in the rate of oxygen diffusion into a patient’s blood because we are ______________________ between the O2 in the air in the lungs and the O2 in the blood.
a.	Decrease:	Increasing the concentration gradient
b.	Decrease:	Increasing the polarity
c.	Increase:	Increasing the concentration gradient
d.	Increase:	Increasing the polarity
e.	None of the above

23.	Children who suffer from a severe deficiency of dietary protein have low levels of the protein albumin in the blood.  Due to this, you would expect their blood volume to be:
a.	Greater than normal
b.	Less than normal
c.	Normal 

24.	Na+ enters kidney tubule cells by moving down its concentration gradient.  This movement of Na+ provides the energy that allows for the entry of glucose into kidney tubule cells.  Considering this, which of the following must be true?
a.	Sodium entry is an example of active transport
b.	Glucose entry is an example of passive transport
c.	Glucose is in a lower concentration inside the kidney tubule cell compared to outside the kidney tubule cell
d.	The entry of glucose is directly powered by the breakdown of ATP
e.	Sodium is in a lower concentration inside the kidney tubule cell compared to outside the kidney tubule cell

25.	Drugs known as thiazide diuretics cause the concentration of sodium in the urine to INCREASE.  As a result, you would expect the urine to:
a.	Have a greater number of sodium particles for each liter of urine
b.	Have a decreased osmolarity
c.	Have a twofold increase in hemoglobin concentration
d.	Have a decreased number of sodium particles for each milliliter of urine
e.	Have an increased concentration of water

26.	You place two cells in a homogenous solution and notice that cell A shrinks while the cell B lyses.  Based on this observation, which of the following could be true?
a.	The solution could contain at least 3 different osmolarities
b.	The solution could be pure water
c.	Prior to entering the solution, the 2 cells were identical in every regard, including protein complement and DNA proscription 
d.	The initial osmolarity of the intracellular fluid of cell A was different than the initial osmolarity of the intracellular fluid of cell B
e.	All of the above are possible

27.	As one’s heart rate increases, one’s blood pressure increases.  A consequence of this is that more fluid is forced out of the blood vessels and into the interstitial space.  This is an example of:
a.	Osmosis
b.	Dialysis
c.	Emesis
d.	Aspiration
e.	Filtration 

28.	Biochemical analysis of the human plasma membrane would demonstrate the presence of:
a.	Very few phospholipids
b.	Large amounts of starch
c.	Excess cellulose if the cell comes from a female individual
d.	Cholesterol
e.	B, C, and D are all correct

29.	Consider the following diagram.  The box represents the dialysis bath.  The tube on the left (Tube 1) carries blood from the individual to the bath while the tube on the right (Tube 2) carries blood from the bath back to the individual.  Suppose this bath is being used to cleanse the blood of excess potassium (K+).  Which of the following is true?
 
a.	The concentration of K+ is likely to be greater in tube 2 than in tube 1
b.	The  concentration of white blood cells is likely to be greater in tube 2 than tube 1
c.	The concentration of K+ is likely to be greater in tube 1 than in tube 2
d.	The concentration of glucose is likely to be greater in tube 1 than in tube 2
e.	A and B both must be true

30.	Individuals with pneumonia can have a build-up of mucus on their lung alveolar membranes – the site of gas exchange.  This should cause the rate at which carbon dioxide leaves the body to:
a.	Increase
b.	Decrease
c.	Not change

31.	The process by which a neutrophil (a type of white blood cell) engulfs a bacterium is best described as:
a.	Endocytosis
b.	Pinocytosis
c.	Exocytosis
d.	Phagocytosis
e.	Leukocytosis

32.	Consider the following diagram: 
Assume the membrane between the 2 compartments is permeable to water but impermeable to solutes.  Which of the following is TRUE?
a.	Water movement will not stop unless the concentration of water is the same in each compartment
b.	Water movement will not stop unless the concentration of solutes is the same in each compartment
c.	Water movement may stop when osmotic pressure is exactly balanced by hydrostatic pressure
d.	All of the above are true
e.	None of the above are true








For questions 33-37, use the following answer choices.  Each choice may be used once, more than once, or not at all.
a.	Active transport
b.	Simple diffusion
c.	Osmosis
d.	Facilitated diffusion
e.	Aspiration

33.	Involves the hydrolysis of a high energy molecule  A

34.	The movement of water towards a solution with a higher tonicity  C

35.	The movement of a nonpolar steroid molecule through the plasma membrane  B

36.	The movement of ascorbic acid, a hydrophilic molecule, across the plasma  D membrane and down its concentration gradient

37.	The movement of oxygen into the mitochondria of a cell  B


Use the following answer choices for questions 38 through 42.  Each choice may be used once, more than once, or not at all.
a.	Haversian Canal
b.	Volkmann’s Canal
c.	Canaliculi
d.	A and B
e.	A, B, and C

38.	May contain large blood vessels  D

39.	May contain cytoplasmic extensions of osteocytes  C

40.	Run(s) along the long axis of a long bone A

41.	Run(s) perpendicular to the long axis of a long bone  B

42.	May run along with or perpendicular to the long axis of a long bone  C


43.	Which of the following is TRUE?
a.	As blood [calcium] increases, calcitonin release decreases
b.	As blood [calcium] decreases, calcitonin release increases
c.	As blood [calcium] increases, parathyroid hormone release increases
d.	As blood [calcium] decreases, parathyroid hormone release decreases
e.	None of the above

44.	The amount of damaged epithelial tissue would most likely be greatest in a:
a.	Closed fracture
b.	Compound fracture
c.	Epidermal fracture
d.	Impacted fracture
e.	Greenstick fracture

45.	Which of the following could be associated with a lack of calcitriol?
I.	Osteomyelitis
II.	Osteoporosis
III.	Rickets
IV.	Acromegaly

a.	I and II
b.	II and III
c.	III and IV
d.	I and IV
e.	II and IV

46.	Healthy bones depend heavily on all of the following nutrients EXCEPT:
a.	Vitamin C
b.	Calcium
c.	Phosphorous
d.	Vitamin D
e.	Vitamin E

47.	If this astronaut returned to earth after a 180 day stay in a weightless space station, you would probably expect him to have:
 		a.	Greatly increased bone mass
				b.	Moderately increased bone mass
				c.	Greatly increased muscle mass
				d.	Decreased bone mass
				e.	Both A and C are correct

48.	Which of the following is NOT dependent upon the skeletal system?
a.	Continuous transport of oxygen to all cells
b.	Manipulation of the external environment
c.	Locomotion
d.	Battling infection
e.	All of the above depend on the skeletal system

49.	Which of the following is NOT part of the axial skeleton?
a.	Floating ribs
b.	Sternum
c.	Clavicle
d.	Sphenoid bone
e.	Ethmoid bone

50.	Which of the following cells would you expect to be highly designed for secretion of collagen?
a.	Osteoclasts
b.	Osteocytes
c.	Osteoprogenitor cells
d.	Osteoblasts
e.	Endosteal reticulocytes


51.	In this picture, we have a lady standing next to an elephant femur.  In the living elephant, which of the following would you expect to contain the most collagen fibers?
a.	The endosteum of this bone
b.	The periosteum of this bone
c.	The reticular dermis of this bone
d.	The papillary dermis of this bone
e.	The stratum spinosum of this bone

 


52.	Which of the following is TRUE?
a.	1 cm3 of spongy bone will weigh more than 1 cm3 of compact bone
b.	Only spongy bone is found at an epiphysis
c.	Only compact bone is found in a diaphysis
d.	Spongy bone lacks haversian canals
e.	The frontal bone consists solely of compact bone


For questions 53 through 56, use the following answer choices.  Each choice may be used once, more than once, or not at all.
a.	Nutrient foramen
b.	Trabeculae
c.	Articular cartilage
d.	Epiphyseal plate
e.	Yellow bone marrow

53.	More likely to be found within the medullary cavity of the tibia than within the E diploe of the sternum

54.	Hyaline cartilage found in a normal 6 year old but not in a normal 36 year old  D

55.	Associated with the blood vessels of the periosteum A

56.	Structure associated with spongy bone but not with compact bone  B


57.	Which of the following bones grows via endochondral ossification?
a.	Parietal bone
b.	Metacarpal bone
c.	Frontal bone
d.	Clavicle
e.	Both B and D are correct

58.	Put the following events of long bone endochondral ossification in the correct chronological sequence.
1.	Formation of an ossification center in an epiphysis
2.	Hypertrophy of chondrocytes within the shaft of the developing bone
3.	Formation of an ossification center in the diaphysis
4.	Closure of the epiphyseal plate

a.	2,1,3,4
b.	3,1,2,4
c.	3,1,4,2
d.	2,3,1,4
e.	1,3,4,2

59.	Which of the following is TRUE?
a.	Osteoclasts play a role in endochondral ossification
b.	Osteocytes lack nuclei
c.	Osteoclasts are derived from osteocytes
d.	The drawback about bone growth in diameter is that any new bone will lack osteons
e.	Bone cannot modify its structure in response to external stresses

60.	Of the 5 following terms, which is NOT associated with the other 4?
a.	Collagen
b.	Bone matrix
c.	Hydroxyapatite
d.	Lacunae
e.	Avascular 

61.	Osteocytes are:
a.	Derived from osteoclasts
b.	Metabolically inactive cells
c.	Found in spongy bone
d.	Not found in the calcaneus
e.	None of the above

62.	Which of the following bones would you expect to contain the largest quantity of immature red blood cells?
a.	Tibia
b.	Fibula
c.	Rib
d.	Talus
e.	Navicular bone of the foot

63.	Gigantism could be caused by:
a.	Hyposecretion of growth hormone by the thyroid gland
b.	Hypersecretion of growth hormone by the thyroid gland
c.	Hyposecretion of growth hormone by the pituitary gland
d.	Hypersecretion of growth hormone by the pituitary gland
e.	None of the above

64.	Which of the following would you NOT expect to occur within an osteoclast?
a.	Production of CO2
b.	Utilization of O2
c.	Secretion of enzymes
d.	Secretion of collagen
e.	Breakdown of glucose
Lesson 7
BODY TEMPERATURE CONTROL

3-26. INTRODUCTION

In order to function properly, the human body must be maintained within a relatively narrow range of temperature.

3-27. SOURCES OF BODY HEAT

Body heat is derived from several sources.

Muscle Contractions. Muscle contractions produce a significant amount of heat. If muscles were very efficient, they would produce energy in the form of contractions and very little heat. Since muscles are inefficient, they produce much heat as they contract. For example, during strenuous physical exercise, the body temperature tends to rise by several degrees.

Metabolic Activity. Another source of heat in the body is certain organs such as the brain, liver, and so forth. These organs produce heat during their metabolic activity.

Solar Radiation. Another source of body heat is solar radiation. When received in excess, solar radiation can cause sunstroke.

3-28. TYPES OF BODY TEMPERATURE

Core Temperature. The core temperature is the temperature within the body proper. Normally, the core temperature is maintained within narrow limits. The core temperature of the blood is continuously monitored by special temperature detectors. These detectors are located in the hypothalamus of the brain.

Peripheral Body Temperature. The temperature of the body surface and the upper and lower members is called the peripheral body temperature. Peripheral body temperature can vary widely. Temperature receptors in the body periphery monitor the peripheral body temperature.

3-29. COUNTERCURRENT MECHANISM

In the limbs of the upper and lower members, the venous blood often has a low temperature. The return of this non-warmed blood to the core of the body might be dangerous. However, within the upper and lower members, the deep veins are generally located adjacent to the major arteries. As the venous blood flows toward the center of the body, it is gradually warmed by the arterial blood coming from the body. This condition is called the countercurrent mechanism.

3-30. REMOVAL OF HEAT

By selecting shady or cool surroundings, an individual can avoid becoming overheated. In other cases, however, the body heat may become excessive. In such cases, if the body is to remain healthy, the surplus body heat must be removed.

Sweating. Sweat (perspiration) is made up primarily of water, with various substances dissolved in it. As one of its physical characteristics, water has a relatively high heat-carrying capacity. In addition, it evaporates from the surface of the body. Another physical characteristic of water is that it removes large numbers of calories during evaporation.

Radiation. In addition, heat can be radiated directly from the surfaces of the body. This is particularly true of the surfaces of the axillae (armpit areas), the inside of the elbow areas, and the groin. These are areas where the skin tends to be thinner than average.

3-31. CONSERVATION OF HEAT

When the ambient (surrounding) temperature is cool or cold, the body must conserve heat rather than remove it.

Less Sweating. An immediate means of conserving heat is to stop sweating. This prevents heat loss by evaporation.

Less Radiation.

In cool surroundings, the superficial capillaries are shut down. Thus, circulation is limited to the deep cutaneous capillaries. Because of the insulating fatty tissues of the subcutaneous layer, these deep cutaneous capillaries radiate much less heat to the surface. 
If the exposed surface area is reduced, there will be less loss of body heat. This can even serve as a lifesaving measure. For example, if an individual has been in cold water (as in a shipwreck or other accident), his body can be folded to reduce exposure. 
Shivering. During shivering, muscles contract without synchronization. Although this produces minimal motion, it produces considerable heat.

Proper Clothing. Obviously, proper clothing is a measure for conserving body heat.

External Heat Sources. External heat sources are commonly used by humans to conserve body heat.

 
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Blood is a specialized fluid connective tissue.  It consists of formed elements (living “cells”) suspended in a non-living liquid matrix, known as plasma.  The formed elements consist of erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.

Blood’s color depends on oxygen content.  It can range from scarlet (oxygen-rich) to dark red (oxygen-poor).  Blood is 5x more viscous (in other words, 5x stickier, and more resistant to flow) than water.  This is primarily due to the presence of the formed elements.  Blood is slightly alkaline (basic) with a normal pH range between 7.35 and 7.45.  Blood’s temperature is slightly higher than body temperature.  100.4F vs. 98.6F.  The average blood volume is 5-6L in male and 4-5L in females.

The main functions of blood can be described as distributory, regulatory, and protective.  

Blood transports: nutrients from the digestive tract and body reserves to all cells; oxygen from lungs to all cells; wastes from cells to elimination sites (CO2 to the lungs, nitrogenous wastes to the kidneys); hormones from endocrine glands to target tissues.

Blood regulates body temperature by controlling the degree of blood flow to the skin’s surface and thus regulating how much heat radiates away from the body.  Blood is responsible for maintaining: normal pH of body fluids; adequate fluid volume in the body; electrolyte balance in the body.

Blood’s protective functions include: preventing blood loss by initiating clotting mechanisms when blood vessel damage occurs; preventing infection by transporting immune cells (leukocytes) and immune proteins. 

Keeping blood “homeostatically okay” keeps interstitial fluid “homeostatically okay,” which in turn keeps cells “homeostatically okay,” and therefore alive.                   
          
Blood plasma is about 55% of blood volume.  90% of plasma is water.  Water acts as a solvent and suspending medium.  Solutes dissolved in plasma include: proteins, nutrients, electrolytes, respiratory gases, and wastes.  

Albumin is the most abundant plasma protein (60%).  It’s produced by the liver and its primary function is to maintain plasma osmotic pressure.  It also acts as a buffer and is involved in the transport of steroids and bilirubin.

Globulins are another variety of plasma protein.  Many are produced in the liver and act as transport proteins for lipids, metal ions, and fat-soluble vitamins.  Other globulins, known as antibodies, are produced by plasma cells (a type of leukocyte) during the immune response.

Plasma also contains clotting proteins.  Most produced in the liver.  Two important examples are prothrombin and fibrinogen.

Other plasma proteins include enzymes, hormones, and other immune proteins.
Plasma contains nutrients – materials absorbed from the GI tract or body reserves and distributed throughout the body.  Includes amino acids, glucose, fatty acids, triglycerides, vitamins, and cholesterol.

Plasma also contains electrolytes (ions, such as Ca2+, Na+, and K+, etc.), respiratory gases (dissolved CO2, O2, and N2), wastes (byproducts of cell metabolism, e.g., urea, uric acid, ammonia, creatinine, and lactic acid), and buffers (chemicals that function to prevent fluctuations in plasma pH).

Red blood cells are small (7.5m diam.), biconcave discs.  The biconcave shape gives them more surface area (good for O2 entry/exit) and increased flexibility.  They are anucleate and lack organelles.  Basically, they are membranous bags stuffed with hemoglobin proteins.  There are normally 4-6 million RBCs per L of blood.  Their primary function is O2 transport.   They also play a minor role in CO2 transport.

Hemoglobin is the protein that is contained in abundance within RBCs.  A small amount of Hb is also found within the plasma.  It reversibly binds and releases O2.  Hb is made up of the protein globin, bound to red heme pigments.  Globin consists of four polypeptide chains, each with their own associated heme group.  Each heme group contains one iron atom that can reversibly combine with one molecule of O2.  Thus, each Hb molecule can transport four O2 molecules.  In lungs, Hb binds O2 and is referred to as oxyhemoglobin.  In tissues, Hb releases O2 and is referred to as deoxyhemoglobin or reduced hemoglobin.  About 20% of blood’s CO2 is transported by combining with the amino acids in the globin portion of Hb.

Blood cell formation is known as hemopoiesis or hematopoiesis.  All blood cells are made w/i red bone marrow. (Adult red marrow is primarily found in ribs, vertebrae, sternum, pelvis, and proximal humeri and femurs).  RBC formation is known as erythropoiesis.  All blood cells arise from the hemopoietic stem cell or hemocytoblast.  In the process of erythropoiesis, a hemocytoblast divides and differentiates.  Its nucleus and organelles are discarded while Hb stores are built up to tremendous levels.

The # of RBCs in the blood stream is remarkably constant and maintained by a negative feedback loop.  Too few RBCs compromises O2 transport, while too many RBCs causes a detrimental  in blood viscosity.  A kidney hormone, erythropoietin (EPO), controls the rate of erythropoiesis.  If blood O2 content , the kidneys release EPO.  EPO stimulates RBC synthesis to .  RBC #  and this  blood O2 content.  O2 delivery to the kidney could change due to RBC count, altitude, increased aerobic activity, lung disease, or cardiovascular disease.

A typical RBC is formed in the red bone marrow from hemocytoblasts.  It travels thru the circulatory system (arteries, capillaries, and veins) and after about 120d, it will have become old and/or damaged. The lack of a nucleus and organelles precludes replication or self-repair.  Old/damaged RBCs are engulfed by scavenger cells, known as macrophages, in the spleen, liver, and red bone marrow.  The Hb within the phagocytosed RBC will be broken down and partially recycled and partially excreted.  Hb is broken down into its globin and heme portions.  The globin is reduced to its constituent amino acids and released from the macrophage into the blood stream for reuse elsewhere.  The iron is removed from the heme and is then transported to the liver by the plasma protein transferrin.  In the liver, the iron is stored.  The remainder of the heme is converted into a pigment called bilirubin.  Bilirubin is released from the macrophage and transported to the liver by albumin.  The liver then modifies bilirubin and secretes it into the small intestine as part of bile.  In the intestine, bilirubin is metabolized by resident bacteria producing metabolites that are eventually excreted in the feces and urine.

Leukocytes are the only formed elements with nuclei and normal organelles.  They account for far less than 1% of total blood volume.  They help protect the body from pathogens, toxins, and cancerous cells.  Leukocytes are formed in red bone marrow.  Like RBCs, they also begin as hemocytoblasts.  Their normal range is 5000-10,000 WBCs per L of blood.  Only a small fraction of the body’s total WBCs are found in the blood at any one time.  Most are in lymphatic organs (e.g., lymph nodes, spleen, tonsils, and appendix) and within the loose connective tissue that underlies the reproductive, respiratory, digestive, and urinary tracts.  They use the blood as a highway to travel from place to place and have the ability to leave the blood stream (this is known as diapedesis) and enter connective or lymphatic tissue where they mount an immune response.  They are capable of flowing thru the tissue spaces with an amoeboid-like motion, and also capable of following chemical cues released by pathogens, damaged cells, or activated WBCs.  This is known as positive chemotaxis.

There are 5 types of leukocytes:  neutrophils, lymphocytes, monocytes, eosinophils, and basophils.  The mnemonic “never let monkeys eat bananas” specifies the 5 types in order of abundance.  WBCs are divided into 2 large classes:  granulocytes and agranulocytes.  Granulocytes contain membrane-bound granules that are stained with a dye known as Wright’s stain.  Agranulocytes do not contain stainable granules.

Granulocytes include neutrophils, eosinophils, and basophils.  All are spherical, larger than RBCs, have lobed nuclei, and stain specifically with Wright’s stain.  Neutrophils are the most numerous circulating WBC.  They constitute 50-70% of the circulating WBC population.  They are 2x the size of RBCs and have a lifespan of 6hrs to a few days.  They contain fine lilac colored granules that take up both acidic and basic dyes, and a nucleus can consist of 3-6 lobes - b/c of this, they are often said to be polymorphonuclear.  Neutrophil count increases during acute bacterial infections.

Eosinophils make up 2-4% of the circ. WBC pop.  They are the same size as neutrophils and have bilobed nuclei.  They take up acidic dyes, which cause granules to turn reddish orange.  Their function is attacking parasitic worms.  They’ll gather around an invading worm and release enzymes stored w/i their granules onto its surface, effectively killing it.  They also act to lessen the severity of allergies by phagocytosing the immune complexes involved in allergy attacks.  They have a typical lifespan of 8-12d.

Basophils make up <1% of the circ. WBC pop.  They take up basic dyes, which causes their granules to turn a dark purple.  Their granules contain the vasodilator histamine as well as the anticoagulant heparin.  Both are released during inflammation.  They have an unknown lifespan.

The agranulocytes lack any visible granules that take up Wright’s stain.  They are the lymphocytes and monocytes.  Lymphocytes comprise 30% of the circ. WBC pop.  They have large, round, purple nuclei taking up most of the cell volume.  They are 1-2x the size of an RBC and have a lifespan of hrs to yrs.  There are trillions of lymphocytes in the body, but only a relatively small # in the blood.  Most are found w/i lymphatic tissues (e.g., lymph nodes, spleen).  There are 2 main types of lymphocytes.  T lymphocytes defend against virus-infected and tumor cells, and control and manage the immune response.  B lymphocytes differentiate into plasma cells, which produce antibodies.

Monocytes comprise 3-8% of the circ. WBC pop.  They are the largest leukocyte – they can be more than 3x the size of an RBC.  They have a lifespan of several months.  They contain pale blue cytoplasm and a dark U or kidney-shaped nucleus.  Monocytes leave the bloodstream to become macrophages – cells specialized in phagocytosis of foreign particles and debris.

WBC synthesis is known as leukopoiesis.  It primarily occurs within the red bone marrow.  The stem cell for all WBCs is the hemocytoblast.  Lymphocytes are also produced w/i lymphatic tissues.

Platelets are fragments (2-4m diameter) of extremely large bone marrow cells that are derived from hemocytoblasts.  Platelets contain membrane-bound granules filled with chemicals important to the blood clotting process.  There are typically 150,000-400,000 platelets per L of blood.  Platelets are sometimes referred to as thrombocytes.  Platelet formation (thrombopoiesis) occurs in the bone marrow.  They remain in the bloodstream for about 10-12d.

Hemostasis is the set of processes that stop bleeding and help heal damaged blood vessel walls.  It consists of 3 events: vascular spasm, platelet plug formation, and coagulation.

Damaged vessels release chemicals that cause the smooth muscle in their walls to contract.  This  BV diameter, which will  blood loss and (by  local blood pressure) facilitate patching and repair.  This event is vascular spasm.

Platelets are activated by the exposure of the collagen that underlies the simple squamous epithelium of the wall of an intact blood vessel.  Activated platelets begin to aggregate at the site of injury.  These aggregated, activated platelets will release chemicals that: enhance vascular spasm; are involved in coagulation; and facilitate the activation and aggregation of more platelets at the injury site (a +feedback process).  The pile of aggregated platelets is known as a platelet plug and provides a temporary seal to the break in the BV wall.  The platelet plug is restricted to the injury site b/c intact endothelial cells release the chemical prostacyclin, which strongly inhibits platelet aggregation.

Coagulation is a complicated multi-step process that results in the formation of a sturdy clot that seals the tear until repairs are complete.  We’ll concentrate on only the final steps.  The final steps are:
A.	In response to a vessel damage prothrombin activator (PTA) is formed.
B.	PTA converts the inactive protein prothrombin into the active thrombin.
C.	Thrombin converts the soluble protein fibrinogen into the insoluble fibrin.  
D.	Fibrin molecules then link to one another and form a meshwork of strands on the platelet plug.  RBCs, WBCs, and plasma are trapped w/i the fibrin mesh.  This results in a blood clot.
There are 2 pathways by which prothrombin activator is formed: extrinsic and intrinsic.  The extrinsic path begins when blood is exposed to a chemical released by damaged tissue cells outside the blood vessel.  The extrinsic path has few steps and, thus, prothrombin activator can be formed quickly.  The intrinsic path begins in response to the release of certain chemicals by damaged blood vessel cells.  The intrinsic path has many steps.   This makes it slower than the extrinsic path, but it allows for amplification, which can yield the production of tremendous amounts of prothrombin activator.  In the body, both pathways typically occur in response to the same event.  Having 2 pathways allows for prothrombin activator to be formed quickly (extrinsic) as well as in large amounts (intrinsic).  Once the fibrin mesh has been created and the clot has formed, clot retraction will occur.  Platelets contain actin and myosin.  They contract.  This compacts the clot and pulls the edges of the torn vessel together (facilitating repair).

Multiple substances are involved in the coagulation process.  Many of these clotting factors are formed in the liver.  Vitamin K is required for their synthesis.  Calcium is also required for coagulation.

Another plasma protein, plasminogen, is involved in fibrinolysis – the breakdown of the clot.  Plasminogen is converted to plasmin, which begins to digest fibrin once repairs have taken place.

Coagulation can be promoted by roughened vessel lining, which can attract and activate platelets.  Also, pooling of blood w/i blood vessels can result in the activation of clotting factors and the initiation of the coagulation process.

Coagulation can be inhibited by aspirin, which inhibits platelet aggregation.  Coagulation is also impaired by vitamin K abnormalities.  This includes chemicals that block the use of vitamin K and lack of absorption of dietary vitamin K (can be due to fat malabsorption).  Broad spectrum antibiotics can impair coagulation because they can kill the resident intestinal bacteria that provide us with much of our vitamin K.  Liver disease impairs coagulation b/c the liver makes the majority of the clotting factors.  Chemicals known as calcium chelators impair blood clotting b/c they bind calcium and prevent its involvement in coagulation.  A low platelet count will also impair coagulation.

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Bone feature Definition 

articular process A projection that contacts an adjacent bone. 
articulation The region where adjacent bones contact each other—a joint. 
canal A long, tunnel-like foramen, usually a passage for notable nerves or blood vessels.
 
condyle A large, rounded articular process. 

crest A prominent ridge. 

eminence A relatively small projection or bump. 

epicondyle A projection near to a condyle but not part of the joint. 

facet A small, flattened articular surface. 

foramen An opening through a bone.
 
fossa A broad, shallow depressed area.
 
fovea A small pit on the head of a bone. 

labyrinth A cavity within a bone. 

line A long, thin projection, often with a rough surface. Also known as a ridge. 

malleolus One of two specific protuberances of bones in the ankle. 

meatus A short canal. 

process A relatively large projection or prominent bump.(gen.) 

ramus An arm-like branch off the body of a bone.
 
sinus A cavity within a cranial bone. 

spine A relatively long, thin projection or bump.
 
suture Articulation between cranial bones.
 
trochanter One of two specific tuberosities located on the femur. 

tubercle A projection or bump with a roughened surface, generally smaller than a tuberosity. 

tuberosity A projection or bump with a roughened surface. 

Several terms are used to refer to specific features of long bones:

Bone feature Definition 

Diaphysis The long, relatively straight main body of the bone; region of primary ossification. Also known as the shaft. 

epiphyses The end regions of the bone; regions of secondary ossification.
 
epiphyseal plate The thin disc of hyaline cartilage between the diaphysis and epiphyses; disappears by twenty years of age. Also known as the growth plate 

head The proximal articular end of the bone. 

neck The region of bone between the head and the shaft. 
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 Lesson 6
CAPILLARIES

10-35. INTRODUCTION

The capillary beds make up the greatest cross-sectional area of the cardiovascular system. In the capillary beds, the actual exchange of materials takes place between the blood and the cells of the body.

10-36. FILTRATION PHENOMENON

The wall of the capillary consists of a single layer of flat cells. The minute spaces surrounding the capillaries and the individual cells of the body make up the tissue space (interstitial/ extracellular space). Fluid passes from the capillary into the tissue space and carries with it various substances. Some of this fluid returns to the capillary on the venous side.

10-37. CAPILLARY SPHINCTERS

The capillary beds are provided with precapillary sphincters that can reduce or completely stop the flow of blood into the capillaries. At the other end of the capillary bed are postcapillary sphincters; when these close, there is a backpressure and more fluid flows into the tissue space.
 
CELL AND TISSUE BIOLOGY EXAM 1
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Introduction to CTB 
Basic Cellular Structures 
Epithelial Tissue 
The Cell Cycle 
Muscle Tissue 
Connective Tissue 

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INTRODUCTORY STUFF
DYES: 

Dye Structure: 
Chromophore Group: The chemical moiety of the dye that is responsible for its color. 
Auxochrome Group: The moiety on the dye that binds to the cellular components. It is usually either amino or SO42- groups. 
Amino auxochrome group = a basic dye. 
Sulfate auxochrome group = an acidic dye. 
Common types of stains: 
Hematoxylin and Eosin (H&E): Most common type of stain. 
Hematoxylin: Functionally a basic dye (despite the fact that it is anionic). It binds to basophilic (negatively charged) nuclear components like DNA and RNA. 
It stains blue 
Eosin: Acidic dye. It binds to positively charged, acidophilic components. 
It stains pink to red. 
Masson (Trichrome) Stain: 
Collagen is green. 
Elastic fibers are red. 
ACIDOPHILIC: Attracted to acidic substances, which are anionic (negatively charged) at physiologic pH. Thus acidophilic substances are positively charged. 

Proteins are acidophilic in at a pH higher (more basic) than their isoelectric point. When the environmental pH is above a protein's isoelectric point, the protein is positively charged and hence acidophilic. 
Many proteins are acidophilic at physiologic pH. 
Acidophilic Components: 
BASOPHILIC: Attracted to basic substances, which are cationic (positively charged) at physiologic pH. Thus basophilic substances are negatively charged. 

Proteins are basophilic at a pH lower (more acidic) than their isoelectric point. When the environmental pH is below a protein's isoelectric point, the protein is negatively charged and hence basophilic. 
Basophilic Components: 
DNA and RNA = basophilic due to presence of phosphate groups. 
Proteoglycans = basophilic due to sugars and esterified sulfates which are negative at physiologic pH. 
Special Types of Staining Techniques: 

Metachromasia: A substance can take on a different than expected color when the substance has two chemically reactive groups that interact due to their close proximity. 
Fat-Staining: To stain membranes and lipid-materials, you must use a fat-insoluble solvent and freeze-fracturing. You can't use paraffin because it would dissolve the substance! 
Common solvents include propylene glycol, and ethanol. 
Sudan IV is a typical fat-soluble dye. 
The Schiff Reagent -- specific for DNA and polysaccharides. 
Feulgen Reaction: This reaction uses Leucofuchsin as a dye, which selectively stains purines in DNA. 
Periodic Acid-Schiff (PAS) Reaction: Selectively stains polyhexoses and hexosamines. Tissues stained by this reaction include: 
Glycogen 
Epithelial mucins in goblet cells. 
Proteoglycans in basement membranes -- but not of the CT matrix. 
Enzymatic Staining: For example, you can visualize mitochondria by testing for the product of a mitochondrial enzyme. The important point is that the enzyme is not stained directly in these procedures. Rather, the localization of its activity is tested for. 
Immunohistochemistry: 
Fluorescent Antibody Technique: Complex a fluorescent dye with an antibody that binds to specific antigens on tissues that you want to visualize. 
Indirect Immunofluorescence: Visualization of a tissue using two antibodies, where the target structure that is actually visualized is bound to the second antibody. 
Indirect Immunocytochemistry: Similar to indirect immunofluorescence, but eliminating the need for fluorescent visualization. 
Protein-A Gold Technique: 
Autoradiography: beta-electrons interacting with silver bromide (AgBr) crystals from radioactive materials illuminates radioactive structures. 
Electron Microscopy: 
Staining is usually with osmium. 
Some sort of fixation is required -- such as Freeze Fracture, in which we cut a preparation into thin slices using a microtome. 


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PLASMA MEMBRANE AND BASIC CELLULAR STRUCTURES
FLUID MOSAIC MODEL: 

RED-BLOOD CELLS GHOSTS: Put a RBC in salt and crack the membrane (i.e. make it leaky) so that all contents leak out. Then reseal the membrane, and we are left with topography maps of the RBC-membrane, showing peripheral and integral membrane-proteins. 

Integral Proteins: 
Glycophorin: Has extensive saccharide groups on the exterior surface. 
It is a single-pass protein. 
Band-III: Peripheral anion channel, exchanging HCO3- out for Cl- in. 
It is a multi-pass integral membrane protein. 
Band-III has no lateral mobility in the membrane -- it is hooked directly to the cytoskeleton via Ankyrin ------> Spectrin ------> Actin spokes. 
Rhodopsin: The "mother" of the 7-pass alpha-helical multi-pass transmembrane protein (of the adrenergic G-protein-bound receptor family). This is a general class of integral proteins and describes a lot of different proteins. 
Peripheral Proteins 
Ankyrin is connected to the inside periphery of the RBC membrane. 
Spectrin is hooked to membrane via Ankyrin. 
Spectrin forms a lattice network composed of alpha and beta dimers. 
It hooks onto Band-III in the membrane (via ankyrin) at one end, and onto Actin at the spokes of the RBC-cytoskeleton in the RBC interior. 
Band 4.1: Another peripheral protein that helps anchor spectrin and actin to the RBC membrane. 
Hereditary Spherocytosis: Hemolytic anemia caused by a failure for RBC's to form a biconcave disc and therefore inability to squeeze through capillaries. 
It can be caused by any of a number of genetic mutations in RBC cytoskeletal proteins. 
One form is caused by a mutation in Ankyrin which results in bad splicing. There is a 2.1 and 2.2 splice out of the same precursor mRNA. 
2.1 splice: predominant in developing cells. 
2.2 splice required in mature cells. 
The 2.2 splice disappears with the missplicing mutation, hence RBC's mature but they don't function when fully developed. 
At the same time, other ankyrin isoforms of the same RNA precursor are translated normally, but they are in other cell-types. 
GLYCOSYLATION: 

N-Linked Glycosylation 
Sugar hooks onto Asparagine Residue. 
Common Sugars attached are N-Acetylglucosamine (GluNAc), and Mannose 
Glycosylation occurs cotranslationally, in the Rough ER. 
PROCESS: 
Core Glycosylation event occurs initially. It involves the linkage of the core oligosaccharide. 
The core oligosaccharide is then associated to the lipid complex, dolichol phosphate. Then it is disassociated and linked to the protein in one step. 
O-Linked Glycosylation 
Sugars hook onto Serine or Threonine residues. 
Common sugars attached are N-Acetyl Neuraminic (Sialic) Acid and N-Acetylgalactosamine. 
Glycosylation occurs posttranslationally, in the Golgi. 
Experiments to Demonstrate the Fluid-Mosaic Model: Lipids can move laterally and can wiggle their hydrophobic tails very rapidly, but they can't flip-flop without a special catalytic reaction (catalyzed by flippase). 

Heterokaryon Experiment: Showed the movement of membrane proteins within the plasma membrane of a human-mouse hybrid. 
Fluorescence Recovery After Photobleaching (FRAP): A way to show that lateral movement of membrane proteins occurs. 
You can determine a Diffusion Coefficient for Lateral Mobility. Some common coefficients: 
Phospholipids in membranes: 1 x 10-8 cm2/sec 
Most highly mobile membrane protein (Rhodopsin): 5 x 10-9 cm2/sec 
You start with 100% fluorescence in membrane, then zap with bleach a little spot on the membrane, and the fluorescence goes way down to about zero. 
Then you can watch the fluorescence recover (back up to near 100%) as adjacent lipids and/or proteins diffuse to the bleached area. 
Restricted Mobility: The cytoskeleton in red blood cells restricts the mobility of many membrane proteins on the RBC membrane. 

Cytoskeletal Elements: Filament Type Size Composition 
Microfilaments 7-8 nm Actin monomers 
Intermediate Filaments 10 nm variable 
Microtubules 25 nm alpha and beta tubulin monomers 
Myosin (Thick) Filaments variable Myosin 


Microtubules: 

Made of dimers of alpha and beta tubulin. They will self-assemble (autopolymerize) under the right conditions. 
Polarity 
(+)-End: Tubulin monomers are, on average, being added to this end. New monomers are put on at a faster rate than they fall off. 
(-)-End: Tubulin monomers are, on average, being removed from this end. Monomers fall off at a faster rate than they are put on. 
Microtubule Organizing Center (MTOC): Often found around centrioles. Microtubules hook to centrioles by their (-)-ends. 
Tread milling Effect: If you label one monomer on a microtubule, it will appear as if it magically moves from the plus to the minus end. 
That's because we keep adding new monomers to the plus end, so it gets pushed further back in the chain, until finally it is all the way toward the minus end and it falls off the chain. 
Anti-Microtubule Drugs: 
Colchicine: Binds to tubulin monomers and thereby prevents assembly of microtubules, killing the cell. 
Taxol: Controversial new anti-cancer drug that works in the exact opposite way as traditional drugs. It stabilizes the microtubule filament so that it can't disassemble. The result is the same, however: microtubule dynamics are lost and the cell dies. 
CYTOSKELETAL MOTOR PROTEINS: ATPases that cleave ATP to cause movement. The microtubules / actin don't move themselves. Rather it is the interaction of the motor proteins with the tubules that causes movement. 

Myosin: Actin-binding protein. 
Dynein: (-)-End Oriented Microtubule binding protein. 
It moves along the microtubules from the (+) to the (-) end. It therefore facilitates retrograde axonal transport. 
Tail is the region that attaches to the microtubules. The Head is the ATPase region. 
Kinesin: (+)-End Oriented Microtubule binding protein. 
It moves along the microtubules from the (-) to the (+) end. It therefore facilitates anterograde axonal transport. 
Cilia/Flagella: The minus end is toward the tip, and the (+)-end is toward the basal body, toward the plasma membrane. 
INTERMEDIATE FILAMENTS: Made of keratins, desmin, vimentin, and neurofilaments. 

NUCLEAR TARGETING of PROTEINS: 

Nuclear Pores: Have specific targeting signals for nucleus-bound proteins. Pores are formed at points where the inner and outer layers of the Nuclear bi-membrane come together. 
EXPT: The Large-T Antigen of the SP40 virus was seen in the nucleus of a host cell by immunocytochemical imaging. 
A mutation on the T-Antigen site, exchanging a Lysine for a Threonine, caused sorting to occur in the cytosol instead. 
Thus this mutation was part of the Nuclear-Targeting Sequence. 
EXPT: Frog oocytes -- the results suggested that the nuclear targeting sequence was on the tail subunit of the nucleoplasmin protein in frog oocytes. 
When the head and tail were dissociated, the tail was able to through nuclear membrane and head wasn't. 
Also, if colloidal gold particles are associated with this tail subunit, they, too, can get into the nucleus, but only if ATP is present. 
SUMMARY: 
Transport into the nucleus does not take place by passive diffusion. It takes by highly specific transport with targeting sequences. 
It appears that nuclear transport is an active process (at least in frog oocytes). It requires ATP. 
ROUGH ENDOPLASMIC RETICULUM: Cytosolic proteins can be synthesized on free ribosomes instead of the Rough ER, per se. However, the following proteins are always synthesized on the Rough ER: 

Membrane Proteins: Using Signal Peptides and Signal Recognition Particles, they are directly translated into the membrane, where they stay. 
Secreted Proteins: They are exuded into the ER lumen, and then onto Golgi and finally secreted in vesicles. They must be synthesized on ER therefore. 
MITOCHONDRIA: Proteins destined for the mitochondria are integrated into the mitochondrial membrane post-translationally. First they are synthesized, and then they go to mitochondria via a vesicle. 

GOLGI COMPLEX: 

Cis Golgi: Earliest part of Golgi, closest to the ER. 
Transition Vesicles often transport material from the ER to the Golgi. 
Middle Golgi 
Trans Golgi: Part of Golgi off of which vesicle bud. 
ENDOCYTOSIS: Clathrin associated with a receptor protein, which in turn associated with the membrane. 

There are several adapter proteins, depending on the membrane to which the vesicle will fuse. For example, there is a specific adapter protein for the Golgi. 
The difference in adapter proteins between 
LYSOSOMAL STORAGE DISEASES: Lots of diseases have at least one etiology where the mutation lies in incorrect sorting of the protein, rather than a non-functional protein itself. 

I-Cell Disease: The Mannose-6-Phosphate recognition marker is found on one of the N-Linked Oligosaccharides of a lysosomal hydrolase. It targets the protein for the lysosome. Adding the M6P is a two step process. 
One enzyme puts on N-Acetylglucosamine phosphate onto a mannose residue. 
A second enzyme then removes the N-Acetylglucosamine, leaving Mannose-6-Phosphate in its wake. 
It is the first step, addition of N-Acetylglucosamine phosphate, that goes wrong in I-Cell disease. 
Cystic Fibrosis: The CFTR protein is mostly getting made, but it is not getting transported to the Golgi. The primary etiology of the disease is a sorting problem, not a defective protein. 
Tay-Sach's Disease: Again, one of the causes is a missorting of the protein beta-Hexosaminidase, where it can't get from ER to Golgi. 
Emphysema and Familial Hypercholesterolemia are two more examples. 
Sucrase-Isomaltase Deficiency: 
The Sucrase-Isomaltase enzyme is normally targeted to the apical epithelial membrane and is involved with disaccharide / glycogen breakdown. 
Individuals with the defect can't metabolize long-chain sugars. 
Again it seems that the secretory pathway for the enzyme is blocked. 


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EPITHELIA
EPITHELIAL CELL TYPES: 

Simple Squamous Epithelium: Kidney Bowman's Capsule 
Resemble fried eggs in shape. 
Simple Cuboidal Epithelium: Kidney Collecting Tubule 
Kidney tubules cells are specialized for absorbing salt and water in an apical to basal direction. 
Simple Columnar Epithelium: GI Tract (Stomach, Jejunum, Duodenum, Ileum) 
Other Tissues: Gall Bladder and Uterine Gland. 
Simple Columnar Cells are specialized for one or all of three things: 
Secretion 
Protection 
Absorption: This is especially true in Duodenum and Jejunum. 
They have oval nuclei toward the basal side. 
SIMPLE COLUMNAR EPITHELIUM CELL TYPES: There are four basic cell types of simple columnar epithelia 
Columnar 
Fusiform 
Basal 
Goblet: = Modified columnar cells that synthesize and secrete mucous. 
Stereocilia are "cilia" that don't move, but they are actually very long microvilli specialized for absorption, and only visible at EM level. 
Pseudostratified Columnar Epithelium: Trachea and Upper Respiratory Tract 
The trachea is actually ciliated, but there are also non-ciliated pseudostratified columnar epithelia. 
Example of Pseudostratified Non-Ciliated Columnar Epithelium: Male Urethra 
Stratified Squamous Epithelium: Salivary Glands, Skin, Vaginal Wall 
There was no example of this in the carousels but only final testing slide. 
Stratified Squamous Keratinized: Layer of Keratin on top, as in Skin. 
Stratified Squamous Non-Keratinized (Mucosal): No Keratin on apical surface, as in Vagina and Mouth. 
Stratified cells form the following layers: 
Basal End: Cuboidal Cells that are proliferative. 
Middle: Polygonal cells held together by desmosomes. 
Apical End: Squamous Cells that are non-proliferative. 
Stratified Cuboidal Epithelium: Sweat Duct of Skin 
Transitional Epithelium: Urinary Bladder 
The tissue appears to transform from 5-8 layers when empty, to 2-4 layers when the bladder is filled. The cells can squish together. 
EPITHELIAL General Characteristics 

AVASCULAR: Epithelial Tissue is generally avascular. 
POLARITY: Epithelial cell have polarity. 
The apical side often contains microvilli and faces the lumen of whatever surface the epithelium lines. 
Microvilli are characteristically found on apical domain. Actin filaments are associated with the microvilli, forming the terminal web. 
Cilia are found on apical membrane, in ciliated cells. 
The basal side is opposite that. A basement membrane, consisting of a basal lamina and reticular lamina, often underlies that. 
The Na+/K+-ATPase pump is characteristically only found on the basolateral membrane. 
BASEMENT MEMBRANE: The basal lamina is visible only at the EM level. The Basement Membrane, on the basal surface, is available at the LM level and consists of the basal lamina plus the underlying connective tissue. 
MESOTHELIUM: Mesodermally derived epithelium that lines body cavities. 
TERMINAL WEB: Visible network of actin filament on the apical end of an epithelial cell. 

JUNCTIONAL COMPLEX: The junctional complex keeps the apical and basal sides of the epithelium separate from each other. 

Zonula Occludens: Tight Junctions. They allow for selective passage of particles, and they prevent particles from getting stuck between cells or getting into the lumen. 
Zonula Adherens: Also present at the junctional complex. 
Macula Adherens: Desmosome. It goes all the way around the circumference of the cell, like a belt or a spotweld. 
TERMINAL BAR: Zonula Occludens + Zonula Adherens. 
Gap Junction: Believed to mediate electronic coupling between cells. Dye can squeeze through a gap junction to get one from cell to the neighbor. 
POLARITY EXPT: Cells lost their polarity by disassociating and then reassociating cells such that they lose their intercellular contacts. 

The Na/K ATPase pump occurs only on the basal membrane of the cell. 
Viral EXPTs: You can also study the distribution of viral proteins to study the host-cell's machinery, since the virus uses the host-cell's machinery. 
People have watched where viral capsid proteins went when they associated with the host plasma membrane. 
The Influenza Virus only distributed proteins to the apical end of an epithelial cell. 
PATHWAYS for Explaining Polarity: Two alternative methods have been figured out. 
Targeting Mechanism where a class of vesicles specifically recognize proteins on the apical domain. Hence some proteins will only merge with membrane on the apical domain. 
Transcytosis: Some evidence also suggests that proteins are initially sorted in the basal domain, and then later transferred to the apical domain via transcytosis. 
EPITHELIAL EXOCRINE GLANDS: 

Unicellular: Goblet Cells are unicellular exocrine glands. 
Simple Tubular 
Simple Branched Tubular 
Simple Alveolar 
Simple Branched Alveolar 
Compound Tubular 
Compound Alveolar 
Compound Branched Tubular 
Compound Branched Alveolar 


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THE CELL CYCLE
Types of Cells Cycles: 

Chromosomal Cycle 
Centrosomal Cycle: The Centrioles duplicate themselves prior to mitosis, and move to opposite poles. 
Cytoplasmic Cycle: Refers to cytokinesis. Distribution and redistribution of cytoplasm. 
Phosphorylation Cycle: Phosphorylation promotes mitosis, as discussed later. 
Nuclear Membrane Cycle: Nuclear Lamins are phosphorylated during Prophase, which causes them to dissociate and results in breakdown the nuclear membrane. 
Nuclear lamins are a form of intermediate filament. 
Nuclear Lamins are dephosphorylated during telophase, so they reassociate and membrane reforms. 
CENTROSOMES: They divide into two before mitosis. 

They form the Microtubule Organizing Center, out of which the mitotic spindle grows, during mitosis. 
MITOSIS: 

Prophase: 
Nucleoli disappear 
Centrosomes split and each daughter forms an aster. 
Prometaphase 
The Nuclear Envelope breaks down. 
Microtubules from each centrosome start interacting with the chromosomes. 
Kinetochore Microtubules from the centromere of each chromosome mature and attach to some of the spindle microtubules. 
Metaphase 
The Kinetochore microtubules align the chromosomes along the metaphase plate. 
The chromosomes are held in place by the opposed kinetochores and their associated microtubules. 
Anaphase 
Kinetochores on each chromosome separate, allowing each chromatid to be pulled toward the poles. 
Anaphase-A: Kinetochore Microtubules shorten. Since the plus end of these microtubules is right at the centromere, this shortening causes the chromosomes to be pulled toward the poles. 
Anaphase-B: Polar Microtubules elongate. The plus end of the polar microtubules face the equator too, but this elongation somehow aids in pulling (or pushing) the poles apart. 
Ca+2 seems to play a role in promoting anaphase. There is high Ca+2 concentration during anaphase. 
Telophase: 
Daughter chromatids reach the poles. 
Kinetochore microtubules disappear. 
Nuclear envelope reforms as nuclear lamins reassociate, condensed chromatin expands, and nucleoli reappear. 
Involves dephosphorylation of many proteins. 
Cytokinesis. 
Actin and Myosin pinch the cell and form a contractile ring. 
Organelles and cytoplasm are distributed evenly. 
KINETOCHORES: Protein masses that form at the centromeres during mitosis, and to which kinetochore microtubules attach. 

SCLERODERMA: These patients produce auto-antibodies that react specifically with kinetochores. 
The Kinetochore Microtubules elongate toward the chromosome! They have their plus-end facing the chromosome, hence they shorten during chromosome separation. 
Both Kinetochores must be attached for the separation to occur. This is a biological safeguard to assure that nondisjunction does not occur. 
CELL FUSION EXPERIMENTS: They provided evidence for activators that promoted mitosis and DNA Synthesis. Cells in different stages of the cell cycle were fused together to see what would happen. 

G1 Cell + S Cell: G1 Cell immediately goes into DNA-Synthesis. 
This is because the S-Cell had S-Phase Activator, which promoted theG1 cell to go into S-Phase. 
G1 Cell + G2 Cell: G1 will go through S-Phase as normal until it reaches G2, then the two cells will go through mitosis together. 
So, the G2 cell waits for the G1 cell to catch up with it. 
This suggests that S-Phase Activator present in the S-Phase is no longer functional in the G2 phase. This is important -- it prevents polyploidy by not allowing cells to synthesize DNA twice! 
G2 Cell + S Cell: Again, S-Phase cell catches up to G2 cell, then they proceed through mitosis together. 
This expt demonstrated that their was no S-Phase Inhibitor in the G2 cell, or else the S-cell wouldn't have completed mitosis. 
Thus there must be some other explanation for why the G2 cell doesn't undergo replication in presence of S-Phase Activator. 
Any Interphase Cell + M-Phase Cell: The interphase cell will prematurely enter mitosis, from any stage, resulting in an abnormal cell. 
This is mediated by M-Phase Promoting Factor (MPF), as below. 
DNA-DAMAGE: When G2 cells are irradiated, their entry into M phase is delayed. They don't enter mitosis until their DNA-repair processes are complete! 
CELIAC DISEASE: Intestinal disease results from abnormalities in intestinal epithelial cell division. 

Cells normally divide at the crypt (basal) region of the cell -- not the apical end. 
For each dividing cell, one daughter will become an epithelial cell and migrate toward apical surface, while the other will remain a crypt cell. 
In Celiac Disease, this process does not occur normally. 
M-PHASE PROMOTING FACTOR (MPF): 

Xenopus Oocyte MPF Levels: 
Oocyte: MPF level is low, in order to freeze egg in prophase, and to prevent mitosis. 
Mature Newly Laid Egg: MPF Level is high 
Early Embryo: MPF levels alternatively high in M-Phase and low in Interphase. 
STRUCTURE: It has two subunits 
CYCLIN: The regulatory subunit. It is produced at a constant rate in the cytoplasm. 
CDC2: The kinase subunit. It phosphorylates targets to induce mitosis. 
CELL DIVISION CYCLE: 
Pre-MPF is an inactive form of Cyclin + CDC2 is sitting around in cytoplasm. 
Active-MPF is made by a combination of two things: 
Kinase Cascade from signal transducers modifies the Pre-MPF in complex reactions (multiple phosphorylations) to active MPF. 
Cyclin levels accumulate in the cytoplasm, as cyclin is continually made in many cell types. 
Mitosis is induced by Active MPF, via the catalytic activity of the cdc-2 subunit. 
Active MPF also produces cyclinases -- cyclin degradation enzymes that lower the levels of cyclin. 
This inactivates MPF, until cyclin is resynthesized or until it accumulates again in the cytoplasm. 


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MUSCLE
SARCOMERE COMPONENTS: 

Z-Disk: The union of two actin heads. 
It demarcates the sarcomere. 
At the Z-Disk, there is no myosin. 
A-Band: The distance of one thick filament, consisting of two myosin filaments. 
I-Band: The distance from the end of one thick filament to the beginning of the next thick filament. 
During contraction, the I-Band becomes shorter. 
The I-Band consists entirely of actin. 
The I-Band marks the margins of two adjacent sarcomeres. Each I-Band technically lies within two sarcomeres. 
H-Zone: The distance from the end of one thin filament to the beginning of the next thin filament. 
During contraction, the H-Zone becomes shorter. 
The H-Zone consists entirely of myosin. 
The H-Zone lies completely within the sarcomere, near the center of the sarcomere. 
ACTIN MYOSIN INTERACTION: In a myofibril, in cross section: 

Six actins can interact with each myosin. Actins are in a hexagonal array. 
Three Myosins can interact, in triangular fashion, with each actin. 
SKELETAL MUSCLE CONTRACTION: Myosin plays the role of an ATPase Actin-Binding Motor Protein. 

We will start with myosin bound to actin. When Myosin is bound to Actin, ATP is bound to the myosin head. 
With ATP bound, Myosin can then detach from the actin thin filament. 
Once detached, the myosin is free to hydrolyze the bound ATP to ADP + Pi. It hydrolyzes the ATP, and the ADP + Pi remain attached to the myosin head. 
The myosin then reattaches to the thin filament. 
Reattachment leads to the release of the Pi group, which in turn strengthens the interaction between the actin and myosin. 
Power Stroke: With the ATP gone, the myosin head undergoes a conformational change, causing the actin and myosin to move relative to each other. 
Then the myosin head releases the ADP. 
Then Another ATP must bind to the myosin, in order for the myosin to release from the Actin to start another cross-bridge. 
If there is no more ATP, Rigor Mortis results, in which the muscle is stuck in the contractile state, with myosin bound to actin. 
REGULATION OF THE CROSS-BRIDGE CYCLE: Regulation is according to intracellular levels of Calcium and is mediated by Troponin Complex and Tropomyosin. 

RELAXED STATE: 
Tropomyosin is bound to the thin filament around its major groove, in the absence of calcium. 
The Troponin Complex is periodically bound to the thin filament such that it blocks the interaction between Actin and Myosin. 
CONTRACTED STATE 
Calcium binds to the Troponin Complex, causing a conformational change in Troponin-C. 
Troponin Complex (Troponin plus tropomyosin) removes itself from the thin filament as a result, such that Myosin can bind. 
ORGANIZATION OF MUSCLE: 

MUSCLE: A whole muscle is surrounded by an epimysium membrane. 
It is composed of a bundle of fasciculi. 
FASCICULUS: Each fasciculus is surrounded by a perimysium membrane. 
It is composed of a bundle of myofibers. 
MYOFIBER (MUSCLE FIBER): Each muscle fiber is surrounded by an endomysium membrane. 
It is composed of a bundle of myofibrils. 
It is a very long and thin single muscle cell. 
It has a sarcolemma plasma membrane, with an endomysium basement membrane beyond that. 
MYOFIBRIL: A bundle of myofilaments, stacked neatly next to each other such that the Z-Disc is lined up. 
Every Thin filament in a myofibril can interact with 3 thick filaments. 
Every thick filament in a myofibril can interact with 6 thin filaments. 
Each Myofibril is bathed in sarcoplasm and surrounded by a sarcoplasmic reticulum from whence it gets it calcium supply. 
MYOFILAMENT: A very long, continuous series of sarcomeres, consisting of actin and myosin. 
Thin Filament: Actin 
Thick Filament: Myosin 
Intermediate Filament: Some muscle fibrils also have some intermediate filaments. 
SKELETAL MUSCLE CROSS-SECTION (Location of Nuclei): The nuclei are all pushed to the periphery, because the actin/myosin fibers take up the central part. 

Compare this to cardiac muscle, whose nuclei are in the center. 
CARDIAC -VS- SMOOTH MUSCLE: Cardiac muscle has nuclei centrally located and relatively more cytoplasm than smooth muscle. 

T-TUBULES: They run in the triad, with sarcoplasmic reticulum on either side, in between each of the individual myofibrils. They transmit the Ca+2 depolarization from the plasma membrane to the SR, which in turn transmits it to all the fibers. 

Ca+2 release from the SR initiates the muscle contraction. 
Ca+2 is pumped back into SR to restore resting, by a Ca+2-ATPase. 
NEUROMUSCULAR JUNCTION: 

Active Zone: Electron-dense (dark in EM scan) patch of membrane at the end of a nerve, right at the neuromuscular junction. 
Note that vesicles are found right at the membrane, while mitochondria are found more proximal, away from the active zone. 
Junctional Fold is right opposite the active zone. 
Ach Receptors on the muscle membrane are highly concentrated right at the nerve terminal. 
MUSCLE DEVELOPMENT: 

Mesenchymal cells form myoblasts. 
Myoblasts proliferate and form myotubes by fusing together, resulting in a large multinucleate cell. 
So, muscle becomes multinucleated by the fusing together of primitive myoblasts. 
SATELLITE CELLS: These cells lie squeezed in-between the endomysium (basement membrane) of a myofibril and the fibers themselves. 

Developmentally they have the same origin as myotubes. They are myoblasts that did not fuse with other myoblasts during development. 
FUNCTION = Muscle Repair. They proliferate to repair damaged muscle tissue. 
They will divide to regenerate muscle, but the regeneration may be incomplete. 
MUSCLE REGENERATION: 
When the muscle fibers are gone, all that is left is the basal lamina and reticular formation of the endomysium. 
The satellite cells then migrate into the empty endomysium. 
Macrophages come in to remove necrotic remnants (debris) 
Muscle regeneration may be incomplete (muscle atrophy or weakness). 
Fiber Splitting can occur, where the satellite cell can generate smaller duplicated myofibril sections from one original myofiber. 
DUCHENNE MUSCULAR DYSTROPHY: Poor function and structure of skeletal muscle. 

Symptoms / Prognosis: 
Hypertrophy of lateral thigh and calf, except that it is not muscle -- it is fatty tissue. 
Death by respiratory failure, usually due to infection and or regurgitation. 
Esophagus malfunction: The skeletal muscle portion of the esophagu1s doesn't function right, leading to problems with swallowing and regurgitation. 
Upper third of esophagus: skeletal muscle 
Middle third of esophagus: Transition of half skeletal and half smooth muscle. 
Lower third of esophagus: Smooth muscle. 
Gower's Sign: Diagnostic test of ability to squat down and stand back up. 
Histopathology: You see necrotic muscle fibers, that ultimately fill with fat infiltrates, giving the pseudohypertrophic appearance to the muscle. 
Pathology: Faulty Dystrophin Gene, resulting focal lesions on the muscle membrane ------> Calcium leaks in the cell ------> perpetual contraction ------> necrosis 
You get contracted myofibers. 
You get swollen mitochondria. 
The fibers remaining (that are not necrotic) are spheroid. 
GENETICS: X-Linked recessive disorder. It is passed from Mother to Son (hemizygous) on the X-chromosome. 
DMD Gene, coding for Dystrophin, is very large. Many of the mutations are new mutations. 
There are brain and cardiac isoforms of the Dystrophin protein. 
Werdnig Hoffman Muscular Dystrophy: Variant wherein a small portion of the dystrophin is missing. In DMD, a large portion is missing. 
DYSTROPHIN: Function is to link the muscle fibers with the extracellular matrix. It function in a spectrin-like fashion, to connect the extracellular matrix with muscle actin. This provides muscle membrane stability. Beyond that function is unclear. 
TREATMENT METHODS: 
Satellite Cell Replacement 
They tried to inject donor satellites to provide donor dystrophin, but the dystrophin couldn't get past the basement membrane barrier to get to the membrane. Using collagenase for this purpose helped but didn't increase muscle strength. 
Viral Infection with the Correct Gene -- severe limitation here was the huge size of the DMD gene. 
Repair Point Mutations on mRNA -- Novel approach where they repair the mRNA to get past the stop codon point, suppling an artificial amino acid at that point. 
In-Vitro Screening: Extract cells from the embryo and test for a particular exon on the DMD gene 
If the embryo had the DMD gene, then a positive PCR product would be obtained (i.e. some of the exons were not there). 
If the embryo did not have the DMD gene, then a negative PCR product was obtained, and they could reimplant the embryo for development. 
PENNIFORM MUSCLE: Muscles with a central tendon, used for strength and stability. Example = Transversus Abdominis. 

FUSIFORM MUSCLE: Muscles with a tendon on either side longitudinally, used for speed. Example = Biceps Brachii. 

Ways of Distinguishing CARDIAC MUSCLE -vs- Smooth Muscle: 

Cross-Section: Cardiac Muscle has a centrally placed nucleus, whereas the nucleus is around the periphery in skeletal muscle. 
Longitudinal Section: Cardiac muscle appears striated, but with branches. 
The cardiac cells are branched in longitudinal section. 
The cardiac cells have the same structural units as skeletal muscle, although SR and T-Tubules won't be as regular. 
In Cardiac Cells you get a diad instead of a triad -- one SR membrane will adhere with one T-Tubule. 
INTERCALATED DISK: The junctional complex that separates cardiac muscle cells. They always coincide with the Z-Line of muscle fibers. 

Fascia Adherens is the basic structural connections between the two cells. 
They are similar to desmosomes but are only found in cardiac cells. 
The Fascia Adherens apparently binds thin filaments in adjacent I-bands to the plasma membrane of cardiac cells. 
Desmosomes: The tightest point of connection between two cardiac cells. 
Gap Junctions: Allows fast electrical conduction between two cardiac cells. 
CARDIAC ISCHEMIA: 

Structural changes in ischemia: 
15 minutes: Structure changes occur. 
30-60 minutes: The cell can still recover. 
> 60 minutes: The cell dies, necrosis. 
Reperfusion Injury: Occurs when oxygen is suddenly replenished after extended deprivation. It can cause mitochondria to swell up and explode. 
Histopathology of Cardiac Ischemia: 
Chromatin is more condensed than normal. 
Mitochondria swell 
Glycogen stores are absent. 
Unlike skeletal muscle, cardiac muscle cannot regenerate. 
SMOOTH MUSCLE: 

Histological Characteristics 
Single central nucleus, but the amount of cytoplasm is less as compared to cardiac muscle, i.e. the nucleus takes up a great space in the cell in smooth muscle. 
Cell is not striated, as actin and myosin are not arranged in linear fashion. 
The amount of actin is greater than that of myosin. Actin is bound to dense bodies in the cytoplasm, which are held in place by intermediate filaments. 
CONTRACTION: 
RELAXED STATE: 
Myosin thick filaments are sparse, i.e. they are not polymerized. 
Myosin is dephosphorylated when relaxed. 
CONTRACTED STATE: 
Myosin Light Chain is phosphorylated. 
Myosin forms more thick filaments 
This allows the dense bodies to move toward each other. 
PROCESS OF CONTRACTION / REGULATION 
Calcium activates Calmodulin Complex. 
Calmodulin Complex then activates the Myosin Light Chain Kinase (MLCK). 
Myosin Light Chain Kinase then phosphorylates the myosin light chains 
DOWN-REGULATION: Here are ways of inducing relaxation or lessening contractile tonicity. 
beta-Adrenergic transduction can phosphorylate the Light Chain Kinase, thus deactivating it ------> No Phosphorylation of Myosin Light chains ------> Less contraction. 
Phosphatases remove the phosphate from the myosin light chain to induce relaxation. 
ACTIN-BASED MOTILITY: 

Pseudopod Movement: Cytoplasmic streaming as mediated by actin polymerization and depolymerization. No myosin is involved. 
Cytokinesis: Once again involves interaction of actin and myosin to pinch the cell. 
MICROTUBULE BASED MOTILITY: Dynein and Kinesin 

Dynein is a minus-end protein. It travels from plus to minus and thus aids in retrograde axonal transport. 
Kinesin is a plus-end protein. It travels from minus to plus and thus aids in anterograde axonal transport. 


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CONNECTIVE TISSUE
COMPONENTS OF CONNECTIVE TISSUE: 

Fibers 
Collagens 
Elastic Fibers 
Ground Substance (Proteoglycans) 
Cells 
Macrophages 
Mast Cells 
Fibroblasts 
COLLAGEN: The primary fiber found in connective tissue. Although other elastic fibers are also found. 

Tropocollagen is the basic structural unit, consisting of three alpha-chains arranged in a helix. 
Tropocollagen shows a typical banding pattern on EM, due to the staggered helices. Procollagen doesn't show the banding pattern. 
Chemistry: 
Every third residue is glycine. 
Hydroxyproline and Hydroxylysine are also prevalent. 
Synthesis: 
Registration Peptide: The registration peptide, distinct from the signal peptide, accomplishes two things. 
It keeps the collagen helix soluble in the cell. 
It allows the alpha-strands to align properly in the cell, in order to form the helix. 
alpha-strands are synthesized in the ER as usual. The signal peptide is cleaved but the registration peptide, as above, remains. 
Post-Translation Modifications: 
Lysyl Hydroxylase and Prolyl Hydroxylase hydroxylate lysine and proline residues. 
Various glycosylations are done. 
Procollagen is formed intracellularly. It is the soluble, spontaneously formed helix that results from the individual strands, after post-translation modifications are made: 
Procollagen still has the registration peptides intact. 
Procollagen is secreted. 
Procollagen Peptidases then cleave the registration peptide extracellularly, to result in Tropocollagen. 
Tropocollagen then forms fibrils spontaneously, stabilized by cross-links. 
Lysyl Oxidase turns on Hydro lysine residues into aldehydes, to stabilize cross-link formation. 
Fibers form by the association of fibrils. 
Collagen Types: 
Collagen I: Skin + Bone 
Collagen II: Cartilage 
Collagen III: Aorta (Reticular Fibers) 
These are also associated with elastic fibers 
A silver stain will only stain reticular fibers, so they can be identified. 
Collagen IV: Basement Membrane 
Basement membranes retain the registration peptide. 
As a result they don't form fibers but instead form sheets. 
COLLAGENASE: Breakdown of Collagen 
Process of Collagen Degradation: 
Collagenase is secreted as a proenzyme and is activated by other proteases. 
It cleaves at a specific site -- about 25% of the way down the molecule. 
The specific cleavage results in the spontaneous denaturation of the collagen helix. The smaller pieces have a lower melting point and are more volatile. 
Other proteases then finish off the job. 
Collagenase activity is temperature and fluid-dependant 
REGULATION of COLLAGENASE: 
Tissue Inhibitors of Metalloproteases (TIMPs): They bind only to activated collagenases, thus moderating their activity through negative feedback. 
Extracellular Proteases: Three types of extracellular proteases aid in the degradation of collagen: 
Metalloproteases. Collagenase is a metalloprotease 
Serine Proteases. For example -- elastase and thrombin 
Cathepsins. 
Collagen-related disorders 
Ehlers-Danlos Syndromes: Hyperextensibility of skin and joints. 
Osteogenesis Imperfecta 
Recessive Dystrophic Epidermolysis Bullosa: Too much collagenase. 
Scurvy: Vitamin-C deficiency leads to malfunctioning prolyl hydroxylase. 
ELASTIC FIBERS: 

Arrangements of elastic fibers: They can be arranged in three different ways 
Fibers / Fiber Bundles -- as in skin 
Lamellae (sheets) -- as in vasculature 
Fine Networks -- as in the lung 
Protein Composition: 
Microfibrillar Protein: Forms the underlying "scaffolding" over which the elastin is laid. 
Elastin: The amorphous, elastic material. 
Elastin is resistant to degradation, except by elastase. 
Desmosine and Isodesmosine: Cross-link elastin, forming a network, and stabilizing the elastin during stretching and compressing. 
Synthesis: 
First, microfibrillar protein lays down the scaffolding. 
Then, elastins get laid down on top. 
AGING: Wrinkles occur as microfibrillar structure is lost 
Emphysema: Loss of elasticity in lung. Rare form = congenital malfunction of elastase in lung. 
GROUND SUBSTANCE: Proteoglycans. They consists of a core protein + Glucosaminoglycans 

Glycosaminoglycans (GAGs): Linear polymers of repeating disaccharides of hexosamine plus a uronic acid such as glucuronic acid. 
GAG-residues are often sulfated. 
SIGNALING FUNCTION: 
GAGs have a high negative charge and are highly hydrophilic. 
Basic Fibroblast Growth Factor (BFGF) can bind to proteoglycans to promote the growth of fibroblasts. 
In this capacity proteoglycans also act as a sieve controlling passage of materials through the ECM. This property is especially important in the kidney. 
Aggrecan: Found in Hyaline Cartilage. 
Perlecan: Found in Basement Membrane 
Syndecan: Found in Epithelial Tissue. It remains attached to the plasma membrane. 
Hyaluronic Acid: Not associated with a core protein itself, but other proteoglycans can associate with it. 
Tissue Distribution: 
Vitreous humor of eye. 
Synovial Fluid of joints. 
It facilitates cell migration during growth and repair. 
Hyaluronidase is secreted when hyaluronic acid is no longer needed. 
BASEMENT MEMBRANES: Made of the Basal Lamina + Reticular Lamina, or two layers of basal lamina. It is visible at the light microscope level, while basal lamina by itself is not. 

Basal Lamina: It provides a substrate for epithelial cells. It consists of different components: 
Lamina Rara: Primary constituent of the basal lamina, composed of two proteins -- laminin and fibronectin. It is directly adjacent to the epithelial cells. 
It is electron lucent in the electron-microscope. 
Laminin: Very large protein it three chains. There are specific binding domains for collagen and heparin. 
Entactin is often associated with Laminin. 
CANCER: Laminin will hook to integrin receptors. In addition it may have its own receptor, which acts in tumor metastasis. 
Fibronectin: Two chains. It is important for wound healing and cell migration. 
There are three forms of fibronectin: 
Plasma Fibronectin: Binds fibrin and fibrinogen, and plays a role in blood clots. 
Cell Surface Fibronectin 
Matrix Fibronectin -- insoluble matrix fibrils. 
Again, it has specific binding domains for heparin and collagen, and it will hook into cellular integrin receptors. 
Lamina Densa: The next layer, underneath the Lamina Rara. Composed mainly of Collagen IV (basement membrane collagen) and Heparin. 
It is electron-dense in the EM microscope. 
Again, Collagen IV still has its globular registration peptide, so it forms meshworks instead of fibers. 
Heparin Sulfate interacts electrostatically with the Collagen IV. 
Lamina Reticularis: The next layer down. Composed of Collagen III and Collagen VII. This makes up the Reticular (elastic) fibers in some basement membranes. 
Collagen III is the main reticular collagen. 
Collagen VII acts as an anchor, to hold the reticular fibers to the basal lamina. 
FNXN: The reticular lamina connects the basal lamina to the underlying stroma. 
Basement Membrane: The very bottom layer of the epithelial layer. 
Integrins: Epithelial Cellular receptors that allow the cells to interact with the basement membrane. 
STRUCTURE: Integral membrane heterodimeric proteins, with alpha and beta subunits non-covalently linked. 
Ligand-binding Domain: Binds to a specific sequence on laminin and fibronectin in the extracellular matrix. 
The specific sequence is Arg-Gly-Asp (RGD) 
Intracellular Attachment: The protein is attached to the actin cytoskeleton, via the following anchor proteins: 
Talin 
Vinculin 
alpha-Actinin 
FUNCTION: Integrins mediate cellular adhesion and migration through the ECM. 
LEUKOCYTE MIGRATION: Part of the inflammatory response. 

Selectins: Specialized glycoproteins on endothelial cells, that serve to attract leucocytes to that location when activated. 
They allow for stronger interaction of the ECM with the leucocyte integrins. 
Cell Adhesion Molecules (CAMs): After being attracted by selectins, the leucocytes interact with CAMs on the endothelial surface. 
The leucocytes binds to the endothelial cell CAMs. 
Activated leucocytes must then secrete proteases and collagenases to migrate through the vessel wall and go to the site of infection. 
WOUND HEALING: 

Plasma Fibronectin binds to the blood clot, thus causing Platelet Derived Growth Factor to be released by the platelets. 
PDGF, along with C5a, then attract neutrophils and macrophages. 
Macrophages then secrete proteolytic enzymes for fibroblasts and smooth muscle cells, so they can get through the debris. 
Then the matrix is restored by fibroblasts, then the endothelial cells are restored. 
TUMOR METASTASIS: Some tumor cells secrete collagenase, thus breaking down basement membranes and allowing the metastatic cells to penetrate the blood vessels. 

FIBROBLASTS: RESIDENT (always present) Connective tissue cells that synthesize collagen, elastin, and basal lamina. 

Fibroblasts are not the only cells that synthesize this stuff. Epithelial tissues and smooth muscle cells can make their own ECM, too! 
Histology: 
They have little cytoplasm and lots of ER and Golgi, which is what we'd expect for their synthetic roles. 
Fibroblast Activating Factor up regulates ECM production in fibroblasts. 
Lymphocytes and monocytes can secrete fibroblast activating factor toward this end. 
ADIPOCYTES: A RESIDENT CELL in connective tissue -- i.e. it is always present. 

White Adipose Tissue: Efficient, low-density storage form for energy. 
It is highly vascularized and innervated. 
HISTOLOGY: Big lipid droplet with nucleus plus minimal cytoplasmic components all off to one side. 
Lipid Deposition (Anabolic): Lipoprotein Lipase frees two of the three fats from triacylglycerols from chylomicrons in the blood. 
The lipoprotein lipase is located in the vascular endothelium. 
The remaining monoacylglycerol stays in the blood and goes back to liver. 
The two freed fatty acids diffuse through the capillary endothelium ------> basal lamina ------> connective tissue ------> adipose basal lamina ------> adipocyte ------> and into the adipose tissue. 
Lipid Mobilization (Catabolic): Hormone Sensitive Lipase is activated via the beta-adrenergic pathway. It frees fatty acids from triacylglycerols in the adipose tissue. 
beta-Adrenergic Pathway means that Hormone Sensitive Lipase is phosphorylated to be activated (via cAMP ------> Protein Kinase, etc.) 
Brown Adipose Tissue: Specialized for thermoregulation. 
It is present in hibernating and newborn humans, but not in human adults. 
Uncoupling Protein uncouples the oxidation of Acetyl-CoA in adipocyte mitochondria, such that no ATP is produced. Instead, the generated electrochemical gradient is dissipated as heat. 
OBESITY: 

Hyperplasia of adipocytes occurs after birth, but the adult doesn't gain or lose adipocytes appreciably. Obesity occurs by hypertrophy of adipocytes. 
Body Mass Index = (Weight (kg)) / (Height (m))2 
Healthy BMI is 23-28. 
Two forms of obesity: 
Android Obesity, weight in upper body and abdomen, is correlated with risks for CHD. 
Gynecoid Obesity, weight in hips and thighs, is not correlated with risks for CHD. 
"Reduced Obese": When an individual gains weight and then loses it again, several things change physiologically which make it difficult to keep off the weight: 
Metabolic needs go down from the original baseline level -- i.e. total daily caloric requirements go down after having lost weight. 
Upregulation of adrenoreceptors occurs -- making it easier to mobilize fatty acids from adipose tissue (that is actually good news). 
BUT, there is a decreased response to hypoglycemia -- catecholamines aren't released as readily. 
LEPTIN: A protein made by adipocytes that correlates with obesity in laboratory mice 
EXPTs in mice suggested that obesity might be due to a lack of leptin. Mice that were obese had no leptin. 
Unfortunately this did not hold the same for humans. Obese humans actually had more leptin, so there was a positive correlation. 
There appears to be Leptin receptors in the hypothalamus, which will be involved with hunger regulation. 
They have also found leptin receptors in the choroid plexus of ventricles. 
ADIPSIN: It forms Acyl-Stimulating Protein (ASP) which generally promotes the building of triacylglycerols. 
Many obese patients have elevated adipsin levels, meaning that they can make fats readily but they have normal or subnormal rates of mobilizing them. 
Tumor Necrosis Factor: Obese patients also seem to have elevated levels of this factor. This is related to development of insulin resistance. 
MAST CELLS: TRANSIENT Connective Tissue Cell. They function in allergic reactions. 

They respond to IgE from plasma cells. 
Histology: 
They characteristically have cytoplasm full of dark-staining granules. 
Mast Cell Granules are released in an allergic reaction. They contain: 
Heparin, an anticoagulant. 
Histamine, vasodilates small vessels, causing increased microperfusion of the tissue (i.e. redness) 
Serotonin 
Leukotrienes 
MACROPHAGES: TRANSIENT Connective Tissue Cell. They are derived from monocytes circulating in the blood. 

Phagocytosis is often mediated by IgG 
Histology: 
Can be distinguished from other transient cells because they usually have foreign materials ingested. 
They have numerous small lipid droplets (vacuoles) 
PLASMA CELLS: TRANSIENT Connective Tissue Cell. They secrete antibodies. 

Morphology / Histology: 
They have a clock-face nucleus. 
They have a perinuclear clear area. 

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CELL and TISSUE BIOLOGY EXAM 3
Download a copy of this study guide 

The Ear 
The Respiratory System 
The Integumentary System 
Gastrointestinal System 
Principles of Development / Development of Eye and Ear 

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THE EAR
EXTERNAL EAR: 

External Auditory Canal: Serve to amplify the original sound wave coming in. 
Cerumen (ear wax) is produced by modified sweat glands in the canal. 
MIDDLE EAR: The middle ear is an air-filled cavity. 

TYMPANIC MEMBRANE: Barrier between external and middle ear. It attaches to the Malleus Bone. 
OSSICLES: Pathway is Tympanic Membrane ------> Malleus ------> Incus ------> Stapes ------> Oval Window. This serves to amplify and focus the sound. 
Middle Ear muscles: 
Tensor Tympani: Muscle attaches to the tympanic membrane, to dampen repeated vibrations and loud sounds, and thus to protect middle ear. 
Stapedius attaches to Stapes and serves same purpose. 
Eustachian Tube: Equilibrates air pressure in middle ear with nasopharynx. 
Otitis Media: Middle Ear Infection with fluid buildup in middle ear. Occurs readily in children due to anatomic immaturity. 
Chronic otitis media can lead to speech problems, due to lost or impaired incoming sound stimuli, which are necessary for speech development. 
INNER EAR: General structure 

Compartmental Divisions: By location 
COCHLEA: Medial and inferior 
Scala Media: Contains endolymph. It divides the Scala Tympani from the Scala Vestibuli. 
Scala Vestibuli: It contains perilymph and is continuous with the vestibule. 
Scala Tympani: The lower section of cochlea, through which "spent" vibrations pass. It contains perilymph, below which exits the round window 
VESTIBULE: Central part of inner ear, containing 
UTRICLE + SACCULE: Detect linear acceleration. 
The Utricle is connected to the Semicircular Canals 
The Saccule is connected to the Cochlea 
SEMICIRCULAR CANALS: Superior part of inner ear; detect angular acceleration. 
Compartmental Divisions: By layer 
Bony Labyrinth: 
PERILYMPH: Fluid between the bony labyrinth and membranous labyrinth, it is continuous with the subarachnoid space and therefore contains Cerebrospinal Fluid. 
High Na+ 
Low K+ 
Membranous Labyrinth: Fits into the bony labyrinth like a sock in a shoe. 
ENDOLYMPH: The Membranous Labyrinth contains Endolymph, which is like intracellular fluid. 
High in K+, low in Na+ 
HAIR CELLS: Both semicircular canals and Organ of Corti contain hair cells as sensory receptors. 

There are two types of hair cells. 
TYPE I HAIR CELLS: Synapses with only one large VIIIth nerve calyx. 
TYPE II HAIR CELLS: Can synapse with multiple VIIIth nerve calices. 
STRUCTURE: Hair cells are bipolar, sort of like epithelial cells (but they aren't epithelia). 
Stereocilia are on the apex of the bipolar neuron. They are the sensory apparatus. 
VIIIth Afferents are at the base (basal end) of cell. 
FNXN: Hair cells have a resting level of activity, which is up-regulated or down-regulated according to which direction the stereocilia move. 
UTRICLE + SACCULE MACULAE: The part of the Utricle and Saccule containing the sensory apparatus. 

STRUCTURE: 
Stereocilia stick up into a gelatinous area, on top of which lie Otolith Crystals (CaCO3). 
Stereocilia lie on top of a hardened Cuticular Plate, which keeps them in place at the base. 
FNXN: Otolith crystals shift and come to rest as you move around ------> deform gelatinous layer ------> move the stereocilia ------> change in membrane potential. 
UTRICLE is adjacent to the Semicircular Canals. 
SACCULE is adjacent to the Cochlea and continuous with the Scala Vestibuli compartment. 
SEMICIRCULAR CANALS CRISTA AMPULLARES: The sensory part of each semicircular canal. 

CUPULA: Stereocilia stick up into a little dome shaped structure in the Crista Ampullares. 
FNXN: The Cupula deflects according to the movement of the Endolymph Fluid inside the semicircular canals ------> move the stereocilia. 
Stereocilia move toward kinocilium ------> depolarization 
Stereocilia move away from kinocilium ------> hyperpolarization 
COCHLEA: 

MODIOLUS: The central "shaft" of the Cochlea, around which it screws. 
The modiolus contains the Cochlear Nerve (VIII) 
SPIRAL GANGLION: The starting point of the VIIIth nerve, it is in the Modiolus at the base of the Spiral Lamina. 
STRUCTURE: Each turn of the Cochlea has three compartments. 
SCALA MEDIA: Endolymph. The Scala Media contains the sensory hair cells and the Organ of Corti 
TECTORIAL MEMBRANE is inside the scala media, right on top of the hair cells. 
FNXN: Shearing Force is created by movement of the Tectorial Membrane across the hair cells. Sound waves cause the tectorial membrane to move. 
The Tectorial Membrane tends to move in an opposite direction as Basilar Membrane. This aids in the shearing force. 
This shearing force transduces the mechanical sound wave into an electrical stimulus. 
Interdental Cells secrete the glycoprotein substance that makes up the Tectorial Membrane. 
STRIA VASCULARIS: Highly vascular epithelium forming one wall of the Scala Media. 
FNXN: It secretes endolymphatic fluid. 
SCALA TYMPANI: In cross section, it is the section below each Scala Media, below the Basilar Membrane. 
BASILAR MEMBRANE: It separates the Scala Media from the Scala Tympani. It forms the base of the Scala Media. 
The Organ of Corti, containing sensory hair cells, lies on the basilar membrane. 
The Basilar Membrane is kept in place by the OSSEUS SPIRAL LAMINA on one end (nearest the spiral ganglion), and by the Spiral Ligament on the other end (nearest the lateral bony wall). 
SCALA VESTIBULI: In cross section, it is the section above each Scala Media, above the Vestibular Membrane. 
VESTIBULAR (REISSNER'S) MEMBRANE: Very delicate membrane separating the Scala Media from the Scala Vestibuli. 
The Scala Vestibuli is continuous with the Oval Window. It therefore conducts sound waves, through perilymph, toward the apex of the Cochlea. 
ORGAN OF CORTI: It is located in the Scala Media, atop the Basilar Membrane. 
INNER HAIR CELLS: Nearer the middle, adjacent to Tectorial Membrane. They are closer to the Modiolus. 
There is usually only one single row of inner hair cells. 
FNXN: These cells are the primary sound receptors. They respond to shearing movements of the Tectorial Membrane. 
Inner Hair Cells send primary VIIIth Afferents into the CNS, via the Spiral Ganglion. 
OUTER HAIR CELLS: There are more of them, located laterally, away from the tectorial membrane. They are closer to the Stria Vascularis. 
They are in multiple rows. 
FNXN: These cells can move the basilar membrane and can "tune" the frequencies of the basilar membrane. 
Outer Hair Cells get input from primary VIIIth Efferents coming from the CNS. These efferents will act on the outer hair cells, causing them to modify the shape of the basilar membrane. 
SUPPORT CELLS: There are lots of support cells besides the ones listed below. 
PHALANGEAL CELLS: Cochlear support cells, both Outer and Inner, corresponding to the Outer and Inner hair cells. 
PILLAR CELLS (RODS OF CORTI): Cochlear support cells. 
DAMAGE to hair cells can occur with loud sounds. This is due to too much movement of the Basilar Membrane. 
FREQUENCY SELECTIVITY: Sound is mapped to different parts of the Cochlea according to frequency. 
Outer part (base) of Cochlea transduces high frequency waves 
Inner part (apex) of Cochlea transduces low frequency waves. 
BENIGN PAROXYSMAL POSITIONAL VERTIGO (BPPV): 

PATHOPHYSIOLOGY: In the semicircular canals, otoliths become dislodged and filter down on top of the Cupula. 
This causes the Semicircular Canals to behave as though they were gravity (linear acceleration) detectors when in fact they are angular acceleration detectors. 
Misplacement of otoliths thus results in Vertigo. 
ETIOLOGY: Idiopathic, by head trauma, or by viral disease 
SYMPTOMS: Vertigo, and no associated hearing loss. 
DIAGNOSIS 
Dix-Hallpike Maneuver is a test for vertigo. Have patient rapidly place one ear down with head hanging off a table. Resultant vertigo makes for a positive test. 
Nystagmus is a sign of dizziness. It should come o, after some latency period, when patient changes head-position. Then, it should go away after a while. 
Electronystagmography (ENG) is a way to quantify Nystagmus. 
TREATMENT 
Physical Therapy do repetitive exercise to fatigue the vertigo response out and desensitize it. Fairly high success rate. 
SURGERY: 
Canal Procedures: Block off membranous portion of inner ear so that cupula cannot move. 
Nerve Section is dangerous procedure 
MENIERE'S DISEASE: 

TRIAD OF SYMPTOMS: Patient will get ringing in ear, then a "fullness" in ear, then hearing loss will drop off, then vertigo. 
Tinnitus (ringing in ear) 
Fluctuating Hearing Loss 
Episodic Vertigo 
ETIOLOGY: Idiopathic, Traumatic, Post-Syphilis, Viral 
PATHOPHYSIOLOGY: 
TRAUMA: Damage to the Endolymphatic Sac; you can't absorb endolymph fluid ------> fluid overload. 
Vestibular Membrane ruptures from buildup of inner fluid and pressure. 
Hair Cell Toxicity then occurs from mixing of endolymph and perilymph fluids. Some cell death. They think the membrane can heal itself, hence resultant hearing loss is only temporary. 
TREATMENT: Most common treatment is medicine designed to decrease the amount of inner ear fluid. 
Salt balance / diuretics play a big role in treatment. 
Meclizine-Antivert, Valium, and Compazine can all be used as Vestibular suppressants. 
SURGICAL: Only if they don't respond well to medicine. 
Endolymphatic Shunt:: A surgical method that enhances the fluid-resorption of endolymphatic fluid. 
Vestibular Nerve Section (not preferred) in the case of severe Vertigo. The problem is that this treatment is only symptomatic. 
Labyrinthectomy: Removal of semicircular canals, resulting in complete destruction of all of VIII -- both Vestibular and Cochlear. 
Oscillopsia is a terrible visual side-effect where people bounce up and down. 
PROGNOSIS: Progressive, untreated Meniere's disease leads to irreversible hearing loss. Early treatment is therefore essential. 
SENSORINEURAL HEARING LOSS: Congenital hearing loss. 

ETIOLOGY: Sometimes the problem is with CN VIII, but more often the problem is with the sensory hair cells. 
MICHEL HEARING LOSS: The worst congenital deafness. No development of cochlea. 
MONDINI HEARING LOSS: Cochlea develops only about 1 turns. 
The resultant hearing-level varies greatly, from nearly normal to virtually deaf. 
SCHEIBE HEARING LOSS: Normal cochlea and vestibule. Problem is strictly with the hair cells. 
NEURAL DAMAGE?: If the nerve is normal, than corrective surgery can be done of some form or another. If the nerve (including the hair cells, which are considered part of the nerve) did not develop or are abnormal, then nothing can currently be done, although some experimental things are being worked on. 
INFECTIOUS HEARING LOSS: Hearing loss from infection. 

TORCH: Toxoplasmosis, Rubella, Cytomegalovirus, Herpes, can all result in hearing loss. 
Meningitis -- probably most common cause of acquired hearing less. 
Syphilis results in endolymphatic hydrops which causes a variety of problems in the inner ear. 


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RESPIRATORY SYSTEM
UPPER AIRWAY EPITHELIA: Pseudostratified Columnar Ciliated Epithelium is throughout the upper airways, with five exceptions. 

EXCEPTIONS: 
Nasal Vestibule 
Olfactory Mucosa 
Nasopharynx 
Epiglottis 
True Vocal Cords 
As we progress down the airways, epithelia gradually change shape: Pseudostratified Columnar ------> Simple Columnar ------> Cuboidal ------> Simple Squamous 
OLFACTORY MUCOSA: Olfactory receptors are located on Superior Concha, adjacent Nasal Septum, and roof of nasal cavity. 

BIPOLAR CELLS: Their nuclei approximately form the middle layer of the mucosa. These are the olfactory nerves. 
Olfactory Cilia: The apical part of the Bipolar Cell. Proximal part forms typical cilia, but the distal parts are the olfactory receptors. 
BASAL POLE: Basal parts of the bipolar cells will go through cribriform plate ------> olfactory bulb 
OLFACTION PATHWAY (proposed): Odorant molecule binds to transmembrane receptor ------> GTP hooks to G-Protein and cAMP is released ------> open ligand-gated cation channels to change membrane potential. 
SUSTENTACULAR CELLS: Their nuclei approximately form the outer layer of the mucosa. 
They are supportive cells with cilia. Function is poorly understood. 
BASAL CELLS: Their nuclei approximately form the lower layer of the mucosa. Supportive cells. Some of them serve as Bipolar-Cell precursors. 
BOWMAN'S GLANDS: Serous glands secrete substance that bathes the odorant chemicals and continuously removes them from nasal mucosa. 
This secretion is necessary for olfaction. You can't smell without it. 
The olfactory mucosa contain no goblet cells and no motile cilia. 
LARYNX: 

TRUE VOCAL CORDS contain Stratified Squamous Epithelium on the anterior aspect. 
FALSE VOCAL CORDS: Normally pseudostratified columnar. Metaplastic epithelia will develop with laryngeal cancer. 
TRACHEA: 

TRACHEAL LAYERS 
Epithelium: Pseudostratified Columnar Ciliated. 
Goblet Cells are found in the epithelium. 
Lamina Propria forms extended, highly vascular basement membrane. 
Submucosa contains numerous mixed (sero-mucous) glands that secrete mucous into respiratory lining. 
Cartilage Rings: Hyaline cartilage forms the outer layer of the trachea, interspersed with fibro-elastic tissue between the cartilage rings. 
BRONCHI: Next several generations 

LAYERS: PRIMARY BRONCHI 
Epithelia: Pseudostratified Columnar, but less tall and with fewer goblet cells than trachea. 
Lamina Propria contains lots of elastins and mast cells 
Histamine / ACh will both cause bronchoconstriction and vasodilation, leading to mucosal swelling and asthma. 
Epinephrine / Atropine will both cause bronchodilation. 
Smooth Muscle layer beneath the lamina propria 
Submucosa which also sort of intermixes with the smooth muscle 
Cartilage: flattened, interconnected plates, rather than C-Shaped rings. 
SEGMENTAL BRONCHI: Epithelia continue to shrink. 
SMALLER BRONCHI: The next few generations, I guess. 
MUCOUS: Functions 

Glycoproteins trap particles in the airways, which are then cleared by epithelial cilia. 
ANTIBACTERIAL: Mucous has several antibacterial agents: 
Peroxidase 
Lysozyme 
Immunoglobulins (not sure which one) 
Lactoferrin 
BRONCHIOLES: At about the 19th generation, you first begin to see small isolated alveoli attaching to the airway. 

LAYERS: 
Epithelia: Simple columnar (shorter) or cuboidal; ciliated. Few or no goblet cells. 
Lamina Propria is much smaller than before 
Smooth Muscle layer is prominent, in highest relative proportion at this level. 
No cartilages. 
CLARA CELLS: Non-ciliated bronchiole cells. 
Prominent SER, possibly related to cholesterol synthesis. 
SURFACTANT PROTEIN A synthesis has been localized to these cells. Of course, no surfactant is found at this level. 
SENSORY CELLS: 
Brush Cells: Non-Ciliated cells in the Bronchioles. They have well-defined microvilli. Sensory function is unknown but proposed. 
Granulated Cells: Contains serotonin, calcitonin, enkephalins, + other neuropeptides. Nerve terminals. 
FNXNS: 
They are proposed to have a sensory function because of nerve terminals: recognition of hypoxia (such as with high altitude) ------> bronchodilation 
They also cause (induce) the differentiation of lung epithelia, via bombesins 
ENDOCRINE CELLS: They aggregate into Neuroepithelial Bodies; they have nerve fibers terminating in the area, and again have proposed sensory features. 
ALVEOLAR DUCTS, ALVEOLI: 

ALVEOLAR CELL TYPES: 
Endothelial Cells (42%): Endothelial cells of pulmonary capillaries are the most prevalent cells 
Interstitial Cells (35%) 
Type II Pneumocytes (13%): Surfactant-secreting 
Type I Pneumocytes (11%): Gas-exchange pneumocytes 
TYPE-I PNEUMOCYTES: Squamous cells that cover about 97% of surface area, because they wrap around the endothelial cells. 
The gas-exchange wall is called the Alveolar Septum 
IDENTIFY: Type-I Pneumocytes won't be typical cellular shape because they are wrapped around. If you can see a cellular shape, then it is either a Tpe-II cell or a Macrophage. 
FNXNS: Primary function is gas exchange 
Reuptake of old surfactant through constitutive pinocytosis. 
REGULATION: In the adult, surfactant secretion is stimulated by hyperventilation and beta-adrenergic agonists. 
TYPE-II PNEUMOCYTES: Surfactant factories; cuboidal epithelia 
LAMELLAR BODIES are released via exocytosis, containing surfactant. Once inside, they unravel and form surface film surfactant. 
Type II pneumocytes are progenitors of Type I Pneumocytes, developmentally. 
PULMONARY CAPILLARY ENDOTHELIAL CELLS: 
FNXNS: 
They make Angiotensin Converting Enzyme (ACE): Which converts Angiotensin I to Angiotensin II ------> potent vasoconstriction. 
ALVEOLAR MACROPHAGES: They're there. Reuptake of surfactant, debris, etc. 
They are carried up to pharynx by ciliary action and swallowed. 
FIBROBLASTS: They're there. They will cause contraction following injury or insult to lung tissue. 
ALVEOLAR PORES of KOHN: Openings in alveolar wall. They serve to equalize intra-alveolar pressure, for communication, and to provide collateral routes for ventilation. 
NERVOUS REGULATION: 
PARASYMPATHETIC STIMULATION: 
Secretomotor to all pulmonary glands except individual goblet cells (which respond to local factors) 
Bronchoconstriction 
SYMPATHETIC STIMULATION: Is bronchodilatory via inhibition of parasympathetics. 
Sympathetics have little effect on pulmonary blood vessels. 
IMMOTILE CILIA SYNDROME (ICS): Congenital impaired ciliary function, not only in lungs but in other places where cilia are required. 

Pulmonary Symptoms: Productive Cough, Sinusitis, Nasal Polyps, Airway Obstruction Other Abnormal Symptoms that often appear with lung disease: 
Non-Pulmonary Symptoms that often also appear: 
Otitis Media 
Situs Inversus -- reversal of location of organs 
Digital Clubbing 
Infertility 
ETIOLOGY: Several structural defects in microtubules can occur. Many of these defects are also common to male infertility. 
STRUCTURAL DEFECTS: 
Dynein defects: Lack of dynein arms in microtubules seems to be most common problem. 
Defects in Nexin links 
Radial Spoke defects 
Microtubular Transposition defects. 
NON-SYNCHRONOUS BEATING: Defects can also occur due to mis-orientation of the direction of the cilia with respect to the basal membrane. 
Basal Foot extends away from basal body in a random fashion rather than an ordered fashion resulting in non-synchronous beating. 
SURFACTANT: Yeah that sexy soapy suds -- surfactant. 

FNXN: Reduce surface tension of alveoli. 
COMPONENTS: 
Dipalmitoylphosphatidylcholine (DPPC): 40% 
Unsaturated Phosphatidylcholine: 25% 
Other phospholipids 15% 
Surfactant-Associated Proteins 10% 
SURFACTANT-ASSOCIATED PROTEINS: 
SURFACTANT-ASSOCIATED PROTEIN A (SAP-A): 
FNXNS: 
Participates in tubulomyelin formation, thus it directly helps reduce surface tension. 
Involved in Receptor-Mediated endocytosis (reuptake) of surfactant 
Activates lung macrophages 
Regulates surfactant secretion 
SAP-A helps prevent bacteria overgrowth in IRDS. 
SURFACTANT-ASSOCIATED PROTEIN B (SAP-B) 
FNXN: 
Inhibits surfactant phospholipid synthesis. 
Aids in reduction of surface tension. 
They are lipophilic and remain in lipid-soluble extracts used for IRDS drug-therapy. 
SURFACTANT-ASSOCIATED PROTEIN C (SAP-C) 
FNXN: 
Inhibits surfactant phospholipid synthesis. 
Aids in reduction of surface tension. 
They are lipophilic and remain in lipid-soluble extracts used for IRDS drug-therapy. 
TURNOVER: Surfactant turns over every few hours. 
Type-I Pneumocytes and macrophages reuptake surfactant. Type-II cells may reuptake some, too. 
REGULATION OF SURFACTANT SECRETION 
MAIN PATHWAY: Glucocorticoids cause fibroblasts to make Fibroblast Pneumocyte Factor (FPF) ------> stimulates Type II Pneumocytes to synthesize surfactant. 
INHIBITORY to pathway: 
Testosterone inhibits Type-II pneumocytes and fibroblasts in this pathway. 
Insulin inhibits the pathway through one or the other cell; thus diabetic mother's fetuses are at higher risk for IRDS. 
STIMULATORY to pathway: 
Estrogen stimulates both Type-II pneumocytes directly, and fibroblasts in this pathway. 
Thyroid Hormone stimulates Type-II cells directly but does not affect fibroblasts. 
INFANT RESPIRATORY DISTRESS SYNDROME (IRDS): Also called Hyaline Membrane Disease 

ETIOLOGY: Premature birth, or delayed or absent surfactant production. 
36-37 weeks (slight premie): surfactant is usually OK. 
28-31 weeks: You see a lot of IRDS babies. 
PATHOPHYSIOLOGY: 
Lack of surfactant causes the lungs to collapse with each breath. 
SYMPTOMS: Look for the following symptoms in the baby 
Tachypnea 
Flaring of the nose 
Cyanosis 
Grunting (to create positive pressure) 
INFANTILE CONSEQUENCES: Cranial Hemorrhage can occur with IRDS, but I'm unsure why. 
ADULT CONSEQUENCES of IRDS: Three classic adult consequences with severe cases 
Chronic Lung Disease 
Neurologic Impairment 
Visual Impairment / Retinal Disease 
TREATMENT: 
HISTORICAL TREATMENTS: 
Continuous Positive Airway Pressure (CPAP): 1970's, increases pressure in lungs and expands them. However, continuous pressure can damage the lungs. 
AEROSOL: Early aerosol contained DPPC but no protein component. 
Bovine Surfactant was developed, containing a protein component which they found was necessary for effective treatment. PROBLEMS: 
There was a risk of contracting infectious disease using it (that's why its no longer used anymore). 
There were antigen problem in interacting with the babies lungs. 
EXOSURF: Synthetic surfactant with no protein component, but with a synthetic substitute. 
It contains DPPC as the detergent, plus Tyloxapol as an agent to replace the protein. 
This drug acts a lot more slowly than agents containing SAP proteins. 
The drug also appears to help prevent bacterial overgrowth (such as pneumonia) that comes with IRDS. SP-A will do the same thing, but Exosurf appears to be a suitable substitute for this function. 
Glucocorticoids are administered before birth, when IRDS is suspect. 
EXOSURF CLINICAL TRIALS were performed with fetal rabbits: 
Experiment Groups: Placebo was plain air. 
Prophylactic Treatment: exosurf -vs- placebo, given to at-risk infants before their first breath. 
Prophylactic Treatment: Three doses exosurf -vs- one placebo 
Rescue Treatment: Exosurf -vs- Placebo, only given once IRDS symptoms set in. 
MEASUREMENTS: If one of the below proved to be true, then prophylactic treatment was not indicated and subject was excluded. 
Lecithin/Sphingomyelin (L/S) Ratio: If it is high enough, it indicates that there is no IRDS. 
Phosphatidylglycerol presence indicates no IRDS. 
RESULTS showed decreased mortality, but residual effects from IRDS. 
Rescue Trials showed that exosurf decreased intracranial hemorrhaging. 
EXOSURF SIDE EFFECTS: 4% adverse side-effects in the trial; generally the drug was considered to be safe. 
LUNG DEVELOPMENT: The lung develops as a lung bud derived from developing foregut. 

ENDODERM: Airway epithelia + alveoli derive from endoderm. 
MESODERM: Cartilages, muscle, blood vessel, pleura derive from mesoderm. 
EMBRYOLOGY STAGES: 
Pseudoglandular Stage: First 16 weeks; all major branches of conducting airways are formed. 
Epithelia are in the form of non-differentiated columnar cells. 
Canalicular Stage: Up to 24 weeks; primitive pneumocytes appear at this stage. 
(Type II) Epithelia are now cuboidal, with lamellar bodies intact. 
Terminal Sac (Saccular) Stage: 24 weeks to term. 
Fully differentiated epithelia. 
LUNG CELL LINEAGE: 
Basal Cell ------> Basal Cell 
Mucous Progenitor ------> Goblet Cell, Clara Cell, Serous Cell ------> Ciliated Epithelia 
Type II Pneumocyte ------> Type II Pneumocyte ------> Type I Pneumocyte 
Type I Pneumocytes develop from Type-II Pneumocytes! 
Endoderm ------> Endocrine Cell 
Monocyte ------> Macrophage 


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INTEGUMENTARY SYSTEM
EPIDERMAL LAYERS: The following layers constitute the EPIDERMIS 

STRATUS BASALE: Contains Stem Cells. Some minimal cell division occurs in this layer. 
HEMIDESMOSOMES: They hook the stratum basale cells to the underlying basal lamina. 
TONOFILAMENTS are through the cells, connected to the hemidesmosomes, forming cytoskeletons. 
Desmosomal Junctions, as well as hemidesmosomes, are prominent between cells. 
STRATUM SPINOSUM: This is the main proliferative layer. Some synthesis begins in this level too. 
Membrane-Coating Granules (MCG) begin formation in this layer, near the top. 
STRATUM GRANULOSUM: This is the mature synthetic layer, where cells are synthesizing the granular components (Keratin, MCG) of skin. 
KERATOHYALIN GRANULES are formed in this layer. 
FILAGGRIN (F) GRANULES: Filaggrin granules will ultimately be released into the stratum corneum. 
Rich in Histidine 
FNXN: Filaggrin causes tonofilaments to clump together. It serves to pack tonofilaments together in cell in the stratum corneum. 
LORICRIN (L) GRANULES: Another Keratin granule. It coats the inner surface of the cell envelope in the stratum corneum. 
Rich in Cysteine 
MEMBRANE-COATING GRANULES (MCG): MCG's are discharged into the granular layer, in the intracellular spaces. 
FNXN: They help make the skin impermeable to water. 
(STRATUM LUCIDUM): Only thick skin, a thin layer of flat cells marking the uppermost border of the Stratum Granulosum. They aren't apparent in thin skin. 
STRATUM CORNEUM: 15-20 layers of dehydrated, non-nucleated keratinocytes, packed with tonofilaments containing filaggrin. 
The cell membrane in the Stratum Corneum is thickened because it is lined with Membrane Coating Vesicles. 
DERMIS: Highly vascular layer underlying the epidermis. 

Cell-Types Found in the Dermis: 
Langerhorn's Cells 
The base of hair follicles 
PAPILLARY LAYER: Immediately underlying epidermis. 
RETICULAR LAYER: Forms the extracellular bulk of the dermis, with lots of capillaries interspersed. 
HYPODERMIS: Below the dermis. Pale-staining because of fat cells. 

This layer is equivalent to gross-anatomy superficial fascia. 
THIN SKIN: Overlies most of the body and contains no stratum lucidum. 

THICK SKIN: Has a prominent (i.e. large) stratum corneum and an identifiable stratum lucidum. 

DISTRIBUTION: Thick skin is primarily found on palms of hand and soles of feet. 
MEISSNER'S CORPUSCLE'S are found in thick skin, in the papillary layer of the dermis. 
It is surrounded by epidermal pegs on both sides. 
They are tactile receptors 
MELANOCYTES: 

DEVELOPMENT: 
They are of neural crest origin. 
Early in development they migrate to the dermis. 
Later in development they migrate to the basal layer of the epidermis, where they remain. 
RACIAL DIFFERENCES: 
The number and nature of melanocytes is relatively constant across races. 
Skin color is determined by the size, number and aggregation-pattern of melanosomes (melanin pigments) present in epithelial cells. 
BLACK SKIN: Large melanosomes, greater in number, and evenly distributed. 
WHITE SKIN: Smaller melanosomes, fewer in number, and aggregated into groups. 
In white skin, many of the pigment granules will be degraded in epithelial cells. 
STRUCTURE: Melanocytes have dendritic processes. 
MELANIN PIGMENT: Multiple types all derive from Tyrosine 
Premelanosomes are assembled from Tyrosinase (from RER) and structural proteins / granules from SER. 
Tyrosinase then transforms Premelanosomes into melanosomes. In this process DOPA is oxidized by tyrosinase. 
EPIDERMAL MELANIN UNIT: Functional unit of one melanocyte, plus around 36 keratinocytes (i.e. skin cells) that it serves. The mature keratinocytes will all have endocytosed melanin from the one melanocyte in the basal layer. 
Cytocrine Secretion is the process by which melanin pigment is exocytosed through the dendritic processes of melanocytes. 
MELANOCYTES -VS- KERATINOCYTES: 
Keratinocytes have extensive desmosomes and hemidesmosomes. Melanocytes don't. 
You can see tonofilaments in keratinocyte cytoplasm. Melanocytes don't have tonofilaments. 
MELANOCYTE STIMULATING HORMONE (MSH): It stimulates (1) melanocyte synthesis and (2) melanocyte cytocrine secretion into epidermal cells. 
ADDISON'S DISEASE: Hyperpigmentation from deficient cortisol ------> increased ACTH (Adrenal Corticotropin Hormone) ------> increased MSH ------> increased melanosomes. 
Addison's Disease is a pathological deficiency of Cortisol, leading to chronically high ACTH. 
LANGERHORN'S CELLS: Antigen-Presenting Cells in the Dermis and Epidermis, derived from bone-marrow. 

DISTRIBUTION: 
Stratum Spinosum of Epidermis 
Dermis 
Hair follicles 
Sweat glands: Apocrine and Sebaceous 
They contain Granules of Birbeck which look like two tennis racquets with handles facing opposite each other (yeah right??) 
MERKEL CELLS: Forms Merkel's DIsk in the stratum basale of the epidermis. 

Neuroendocrine cell; it is considered to be a sensory receptor. 
PACINIAN CORPUSCLE: Located in the dermal-hypodermal junction -- very deep. They are mechanoreceptors. 

HAIR: 

Three hair types: 
Lanugo Hair: Prenatal hair; very fine and unpigmented. 
Vellus Hair: Pre-pubescent, non-pigmented hair; peach fuzz. 
Terminal Hair: Hair on scalp; and adult pubic and axillary hair. 
DEVELOPMENT: Pilosebaceous Apparatus grows as a downgrowth of the epidermis that pokes into the dermis. 
Apocrine Sweat Glands, Arrector Pili, and sebaceous glands grow in association with this downgrowth, surrounding the hair follicle. 
CELL-TYPES: 
Inner Root-Sheath Cells grow in the same fashion as epidermal cells. 
Cuticle Cells accumulate large granules but no tonofilaments. 
Cortical Cells have tonofilaments but no granules. 
Medullary Cells have huge granules but no tonofilaments. 
HAIR GROWTH CYCLE: 
ANAGEN PHASE: Growth period extends for 2 - 6 years. 
80-90% of hair is in this phase at any point in time. 
CATAGEN PHASE: Regression period takes 2 - 3 weeks. 
TELOGEN PHASE: Resting period takes 3 - 4 months. 
10-20% of hair is in this phase, and is thus shedding. 
After Telogen phase, the old hair shaft is shed and a new one appears. 
SWEAT GLANDS: 

SEBACEOUS GLANDS: 
SECRETION: HOLOCRINE The entire cell is lysed and secreted as sebum. 
FNXN of sebum may be water-barrier or bacteriocidal. It is not clear. 
Sebaceous glands begin secretion at puberty. 
MEROCRINE (ECCRINE) GLANDS: 
SECRETION: Glands open into sweat ducts that carry sweat to skin. 
MUCOUS and SEROUS glands are both present in merocrine glands. 
DISTRIBUTION; Virtually everywhere on body except genitals. High concentration in thick skin of palms of hand and sole of foot. 
SWEAT composition: Hypotonic, with active ion resorption in the ducts. 
STIMULATION of eccrine sweat glands is cholinergic 
STIMULATED by heat primarily (thermoregulation) but also by anxiety (as in sweaty palms). 
APOCRINE GLANDS: 
DISTRIBUTION 
Axilla 
Anogenital Region 
Eyelid 
External Auditory Meatus 
STIMULUS is both adrenergic and cholinergic. 
STRUCTURE: The sweat ducts open into hair follicles, and myoepithelial cells help secretion. 
SECRETION: Odorless when excreted, but smells like body odor once it has undergone bacterial decomposition and fatty acids are created. 
NAIL: 

Nail Bed underlies the nail. 
Nail Bed Epithelium looks like skin but has no granulosum layer. 
Hyponychium: skin underlying the tip (distal edge) of the nail. 
Paronychium: Lateral nail folds; skin around the lateral edge of the nail. 


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GASTROINTESTINAL
LAYERS OF THE GI TRACT: 

MUCOSA: Composed of three layers 
EPITHELIUM 
LAMINA PROPRIA: 
MUSCULARIS MUCOSA: Smooth muscle intermixed with the lamina propria. 
FNXN: Contraction of the muscularis mucosa allows for epithelial motility; mixing, propulsion, etc. 
SUBMUCOSA: Collagenous connective tissue; vascular tissue; glands 
SUBMUCOSAL PLEXUS: Enteric nerves in the submucosa. 
MUSCULARIS EXTERNA: 
MUSCULARIS CIRCULARIS: Circular Layer 
MYENTERIC PLEXUS: Enteric nerves between the two layers of external muscle. 
MUSCULARIS LONGITUDINALIS: Longitudinal Layer 
ADVENTITIA (SEROSA): Several layers of loose connective tissue; the mesentery. 
ESOPHAGUS: 

MUSCULATURE: 
Upper 1/3 SKELETAL 
Middle 1/3 is Skeletal + Smooth 
Lower 1/3 SMOOTH 
EPITHELIUM: The esophagus has stratified squamous epithelia. 
So does the oral cavity and anus. The rest of GI has simple columnar epithelium. 
STOMACH: 

STRUCTURE: It has a thick muscularis layer and thin submucosa. 
CELL TYPES: 
PARIETAL (OXYNTIC) CELLS: 
RESTING: Parietal cell has TUBULOVESICLES and abundant mitochondria. Tubulovesicles are the acidic vesicles that are later exocytosed. Three ion channels create the acid: 
H+/K+-ATPase pumps H+ into lumen of vesicle. 
Carbonic Anhydrase provides the source of H+ (and HCO3- which exits as alkaline tide) 
Cl--Channel ejects Cl- into lumen (to form HCl) 
Na+/K+-ATPase maintains concentration gradient. 
ACTIVE: Tubulovesicles fuse with the apical plasma membrane to exocytose the H+. This forms INTRACELLULAR CANALICULI near the apical membrane. 
Tubulovesicles are no longer present in active parietal cells. 
Active parietal cells have long, secreting microvilli on the apical surface. These microvilli essentially were the former tubulovesicles. 
Tubulovesicles can be distinguished from microvilli because microvilli have actin in them and tubulovesicles don't. 
MUCOUS NECK CELLS: Are located along the villi of the stomach. 
MUCOUS is made of proteoglycan which forms a slippery film that protects stomach epithelium from acid. Functions in the stomach and intestine: 
Protection from digestive enzymes 
Provides HCO3- pH buffer from acidic chyme 
Provides a sticky environment for IgA to stick to 
Lubricant 
CHIEF (ZYMOGENIC) CELLS: Secrete pepsinogen. From cuboidal to pyramidal in shape. 
ENTEROENDOCRINE CELLS: Secrete a variety of hormones into GI-System. 
They have reversed polarity, as they secrete the hormones into the blood space rather than GI-Lumen. 
G-CELLS secrete gastrin. 
E-CELLS secrete somatostatin. 
HELICOBACTER PYLORI: Implicated in lots of diseases. 
Gastric Ulcers; Gastric Cancer; Duodenal Ulcers; Gastritis 
MECHANISM: Proposed is that bacteria are ingested and get into stomach epithelium ------> cause inflammation which increases permeability of gastric mucosa ------> acid invades and you get gastritis symptoms and ulcers. 
OMEPRAZOLE: H+/K+-ATPase blocker for ulcers. 
ANTIBIOTICS are employed to fight H. Pylori. 
GASTRIC RESTITUTION: Acid-damaged gastric epithelia are replaced by new tissue. 
Epithelia extend lamellipodia which stretch out over to cover the denuded area. 
Lamellipodia mechanism involves actin and cytoskeleton reorganization. 
PYLORUS: We must be able to distinguish Pylorus from Body of Stomach: 
The Pylorus has very shallow gastric pits or none at all. 
The Pylorus mas more highly branched glands -- almost exclusively mucous. 
SMALL INTESTINE: 

CELL-TYPES: 
ENTEROCYTE: The principle absorptive cell, simple columnar epithelium. 
ULTRASTRUCTURE: 
It contains brush-border disaccharidases and peptidases which complete luminal digestion before absorbing nutrients. 
BASAL MEMBRANE: Facilitated diffusion occurs to transport the nutrients into the blood. Concentration gradient for this diffusion is maintained by constant influx of new nutrients. 
Glycocalyx: Rich carbohydrate layer on apical membrane that serves as protection from the digestional lumen, yet it allows for absorption. 
Terminal Web provides cytoskeleton; the cell is a polar epithelial cell. 
CARBOHYDRATE ABSORPTION: 
GLUCOSE / GALACTOSE: Na+-Cotransport 
FRUCTOSE: Facilitated transport 
PENTOSES (RIBOSE): Passive diffusion 
AMINO ACID ABSORPTION: Generally also Na+-Cotransport. 
FAT ABSORPTION: 
EMULSIFICATION by micelles. Bile salts facilitate the attachment of Pancreatic Lipase to the lipids. 
There is an unstirred water layer right at the villus border. Due to its detergent properties, micelles can penetrate that border. 
DIGESTION: PANCREATIC LIPASE then breaks down the triglyceride ------> monoglyceride + free fatty acids. 
Fatty Acids diffuse through enterocytes by simple diffusion. 
RE-ESTERIFICATION: Fatty acids are re-esterified to triglycerides inside the enterocytes. 
CHYLOMICRON FORMATION: Chylomicrons are formed as protein coats + cholesterol is added to the triglyceride. 
LYMPH: Chylomicrons enter circulation through lacteals ------> lymphatic system. 
Short Chain fats go directly into the portal blood -- not into lymph. 
GOBLET CELL: Secretes mucin in the small intestine. Unicellular exocrine glands distributed all along the villus. 
MUCOUS NECK-CELLS: See stomach. 
PANETH CELL: Protective, bacteriocidal cells that secrete lysozyme to break down bacterial cell walls. 
CRYPTS: Paneth cells are located strictly in Crypts of the villi. 
M-CELL: Overlies Peyer's Patches. Samples the gut lumen and transports it to the submucosa for sampling by Peyer's Patches. 
M-CELL do this by transcytosis of materials. 
Orally administered vaccines have promise to fight several diseases by this mechanism: Orally ingest antigen ------> M-Cell uptake ------> Peyer's Patches ------> Antibody production. 
ENTEROENDOCRINE CELLS: 
BRUNNER'S GLANDS: Produces alkaline fluid (HCO3-) which neutralizes stomach acid. Brunner's glands are localized to the crypt. 
CELL-RENEWAL / MIGRATION: Enterocyte lifespan is 4-6 days. 
CRYPT: Contains small population of self-renewing stem-cells that divide infrequently. 
These stem cells are the progenitors for nearly all 
VILLUS: Contains proliferative, migrating cells that divide frequently. 
Most cell types migrate upward toward the villus: 
Enterocytes 
Enteroendocrine Cells 
Paneth cells migrate downward toward the base of the crypt. 
PLICAE CIRCULARIS: Grossly visible folds in the small intestinal lining. 
This, coupled with villi and microvilli, make for a 600-fold increase in total absorptive surface area. 
VILLI: 
VILLUS CELLS: They are primarily absorptive -- i.e. enterocytes. 
CRYPT CELLS: They are primarily secretory. Small intestinal secretion occurs in the crypt. 
PEYER'S PATCHES: Lymphoid tissue in submucosa. The ileum has the highest concentration of Peyer's Patches. 
There is a flattened epithelium over Peyer's patches in the ileum, instead of columnar. 
Crypts of Lieberkühn: Deep crypts in small intestine that contain many goblet cells and few absorptive cells. Just another term for the villous crypts found in the small intestine. 
CHOLERA: 

CHOLERA TOXIN STRUCTURE: 
BINDING SUBUNIT: Binds to the sugar portion of Ganglioside, GM1. 
ACTIVE SUBUNIT: It is inserted into membrane once other subunit is bound. 
It ADP-Ribosylates Apical Cl- channels, blocking them OPEN ------> continual cAMP 
HIGH cAMP LEVELS result in severe secretory diarrhea by two pathways: 
Phosphorylates apical Cl- channels ------> keeps them OPEN ------> secretory diarrhea 
Phosphorylates apical Na+/Cl- Cotransporters ------> keeps them CLOSED ------> prevents Na+ from reentering. 
ORAL REHYDRATION THERAPY: Administer glucose solution, to facilitate Na+ resorption (and hence water) via Na+-Glucose reuptake. 
STARCH is even more effective than glucose, because it is equivalent in terms of its tonicity yet it provides a lot more glucose to the enterocytes for more water resorption. 
LARGE INTESTINE: 

The large intestine has no villi or lamina propria, and the majority of Large Intestinal cells are goblet cells. 
FNXN: Water resorption by active Na+ transport. 
Acetylcholine will stimulate cell Goblet Cell secretion. Lost membrane is continually replaced by constitutive pinocytosis. 
SMALL INTESTINE -VS- LARGE INTESTINE: The Small Intestine has a lamina propria and villus, while the large intestine does not. This is the distinguishing feature between the two. 
SALIVARY GLANDS: 

SALIVA: 
Salivary Amylase: Secreted primarily by Parotid gland. 
Amylase normally operates at pH 7-8 and is therefore inactivated once in the stomach. However, if it is inside a bolus of food and protected on all sides then it can still be active even in stomach. 
Mucus: Secreted by the other glands (Mandibular and sublingual). 
FNXN: Lubrication of food and it serves as a buffer. 
Lactoferrin: Binds Fe in mouth, preventing bacteria from getting it. It thereby serves as an antibacterial role. 
Lingual Lipase: Released from tongue itself, allows easy movement of fats on the tongue. 
It can serve a backup function in case pancreatic lipase is lacking. 
Secretory IgA: Antibacterial secretions. 
Lysozymes: Antibacterial secretions. 
SALIVARY DUCTS: 
CELL TYPES: 
ACINAR CELLS: Secretory cell secretes saliva into ducts. 
MYOEPITHELIAL CELLS: Contractile cells extend over the acinar cells and ductal cells. 
(SEROUS CELLS): Secrete clear substance containing protein. 
Their cytoplasm stains well. 
Indistinct cell boundaries. 
Parotid Gland is strictly serous; primary secretory of amylase. 
(MUCOUS CELLS): Secrete mucous. 
STRUCTURE: Larger, triangular with apex of triangle projecting toward the lumen of the salivary duct. 
SALIVARY DUCTS: Membrane is water-impermeable ------> hypotonic saliva. 
INTERCALATED DUCTS: They have low cuboidal epithelium and associated myoepithelium. 
STRIATED DUCTS: Contain Striated Ductal Cells: simple columnar. 
They are specifically responsible for resorbing Na+ to aid in hypotonic solution. They have characteristic basal infoldings associated with this function. 
INTERLOBULAR DUCTS: Join the main excretory duct that leads to oral cavity; stratified cuboidal or stratified columnar 
PATHWAY of SALIVATION: Acinus ------> Intercalated Ducts ------> Striated Ducts ------> Interlobular Ducts ------> Oral Cavity. 
Parotid Gland: Strictly Serous 
Submandibular Gland: Mixed Seromucous 
Sublingual Gland: Mixed seromucous, but mucous predominates. 
SECRETORY IgA: An immobilizing antibody that "traps" pathogens to stop their activity. 

STRUCTURE: 
Two monomeric IgA molecules attached by a J-Chain. This structure is assembled by the antibody cell. 
J-Chain gives protease resistance to the molecule so it is not so rapidly degraded. 
Secretory Component is made by the enterocyte epithelial cell. 
PROCESS: 
Secretory component starts off as an enterocyte membrane receptor. 
Receptor-Mediated Endocytosis of the IgA from the blood space. 
The IgA-Receptor Complex is then cleaved, leaving part of the secretory component on the IgA. This is now called Secretory IgA. 
The secretory IgA is then exocytosed into lumen. 
ORAL TISSUES: 

Filiform Papillae: Anterior 2/3 of tongue, covering most of surface; no taste buds. 
Conical in shape. 
Fungiform Papillae: Scattered among the filiform papillae. Taste buds may be found on them. They are larger and more vascular. 
VON EBNER'S GLANDS in tongue secrete lingual lipase. 
Circumvallate Papillae: Posterior 1/3 of tongue, along V-Shaped dividing line between anterior-and posterior of tongue. They have lots of taste buds. 
PANCREAS: 

EXOCRINE PANCREAS: PANCREATIC ACINAR CELLS 
GRANULE MATURATION: Secretory proteins "mature" as they progress through the RER and Golgi, and form into granules. 
Condensing Vacuoles are the names of the early secretory granules (containing digestive zymogens) that bud off from the trans-Golgi. 
MATURATION at that point serves two purposes: 
Maturation allows the granules to become relatively anhydrous so that they don't become proteolytically active intracellularly. 
Maturation also allows for compact, efficient storage of zymogens 
Mature Granule is stored in apical part of cell until stimulated for secretion. This is different than hepatocytes which do not store granular material. 
Junctional Complexes create polarized cells; exocytosis only occurs at the apical pole of the cell in pancreatic acinar cells. 
This is again different than hepatocytes, where exocytosis occurs at both ends. 
PANCREATIC SECRETION: 
TANNIC ACID EXPTS: Exocytosis in Pancreas is constitutively balanced by endocytosis. 
Tannic Acid causes proteins to precipitate so that we can "capture" exocytosis in action. 
Tannic also inhibits endocytosis. 
Thus under the influence of Tannic Acid, the pancreas will exocytose all of its membrane! 
SECRETOMOTOR STIMULATION: The pancreas undergoes regulated secretion, via CCK, Secretin and ACh 
Secretin, VIP: beta-Adrenergic secretion (cAMP ------> PROTEIN KINASE A) 
CCK, ACh: alpha-Adrenergic secretion (IP3 ------> Ca+2 ------> PROTEIN KINASE C) 
Both act synergistically, i.e. the whole is greater than the sum of the parts 
CONSTITUTIVE EXOCYTOSIS of fluid occurs at the same time as exocytosis of zymogens. Fluid is required to put the zymogens in aqueous environment and thus make them enzymatically active. 
PANCREATIC DUCTS: They modify the acinar secretion by exchanging HCO3- for Cl-, yielding an alkaline secretion. 
Pancreatic Ducts are interlobular ducts. 
ENDOCRINE PANCREAS: ISLET CELLS (Insulin, Somatostatin, Glucagon) 
Endocrine Secretion is less regulated in the pancreas. Secretion is constitutive into the extracellular space, and then hormones are simply absorbed by plentiful capillaries in the region. 
PANCREATITIS: Digestive enzymes wind up getting activated intracellularly and thus destroy pancreatic acinar cells from the insides out. 
Mostly associated with chronic alcoholism 
DIAGNOSIS: Pancreatitis will be shown by high serum levels of digestive enzymes, which shouldn't be in the blood! Pancreatic Amylase is usually tested for. 
CYSTIC FIBROSIS: Pancreatic duct can get clogged, because bicarbonate secretion fails and HCO3-/Cl- channel is faulty. 
CF patients often have little or no pancreatic function remaining. They can take enzyme tablets along with a modified diet to overcome the deficiency. 
PANCREATIC INSUFFICIENCY: It takes 95% insufficiency of the pancreas before severe malnutrition results. There is great redundancy in digestive capacity of enzymes and amount of enzymes secreted. 
ZYMOGEN ACTIVATION CASCADE: Enterokinase is expressed on the brush border of intestinal enterocytes -- not in the pancreas. It starts the activation cascade. 
LIVER: The liver is both an endocrine (liver enzymes) and exocrine (bile) gland, performing both secretory and absorptive functions. 

HEPATOCYTE: Epithelial cells with distinct domains 
APICAL POLE faces Bile Canaliculi. 
BASAL POLE faces Liver Sinusoids 
LATERAL MEMBRANE: Gap junctions allows intracellular communication. 
SINUSOIDS: Liver discontinuous and fenestrated endothelial cells. 
SPACE OF DISSE: The extensive space between the sinusoid and hepatocyte, through which rather large particles can traverse. 
The Space of Disse is filled with microvilli from the hepatocytes. These microvilli will perform both absorptive and secretory functions in interacting with the blood. 
ABSORPTIVE: Absorb digested nutrients from portal blood. 
SECRETORY: Secrete liver enzymes 
KUPFFER CELLS: Hepatic Macrophages found in the sinusoidal space. 
They degrade senescent erythrocytes ( ------> spleen), as well as typical immunological functions. 
SECRETIONS: 
ENDOCRINE SECRETIONS: Albumin plus tons of others are secreted into the Liver Sinusoids. 
Liver enzymes are secreted by unregulated constitutive exocytosis. The process of secretion is not regulated. Regulation of liver enzymes occurs only at the synthetic level. 
Apoprotein is also made in SER. Hepatocytes use it to make VLDL particles from chylomicrons that arrive to the liver from the blood. (The chylomicrons first travel from lymph into general blood circulation before reaching the liver). 
BILE SECRETION / RESORPTION: Bile is secreted into the Bile Canaliculi and resorbed into the bile canaliculi. 
Bile Ducts add HCO3-, making the bile alkaline. 
Bile Canaliculi are lined with microvilli. 
BILE SECRETION is via facilitated diffusion through apical pole. 
BILE ABSORPTION: Bile absorption is done via Na+-Cotransport on the sinusoidal membrane. They think that bile salts are hooked into apoproteins. 
DETOXIFICATION: Occurs at the Smooth ER. Excessive toxicity will lead to proliferation of the Smooth ER, as sign of liver pathology. 
Conjugation of bilirubin to bilirubin glucuronide. 
Addition of glucuronides and sulfates to other toxins and/or drugs 
LIVER ORGANIZATION SCHEMES: 
COUNTERCURRENT FLOW: Blood travels in the opposite direction as bile, making it energetically more efficient for both. 
BLOOD: Portal Vein + Hepatic Artery ------> Sinusoids ------> Central Vein ------> IVC 
BILE: Hepatocytes ------> Bile Canaliculi ------> Hepatic Duct ------> Common Bile Duct 
Incoming (resorbed) bile acids are most concentrated in the most proximal (nearest portal triad) section of each lobule. They will travel down their concentration gradient to reach the bile canaliculi and be resecreted. 
LIVER LOBULE: Classic organization 
CENTRAL VEIN: Carries blood away from the liver. Each lobule has a central vein. 
PORTAL TRIADS (Hepatic Artery branches, Portal Venules, Bile Canaliculi) carry blood to the liver. 
SINUSOIDS are throughout the middle of the lobule, interspersed with HEPATOCYTES. 
Again, blood flows from the portal triad, through the center of the lobule, to the central vein. 
PORTAL LOBULE: The triangle formed by the Central Veins of liver lobules at each vertex, and a Portal Triad in the center. 
This organization emphasizes the functional properties of the liver: All blood within the Portal Lobule Triangle originates from the Portal Triad in the center. 
Thus this organization is an approximate "map" of the blood flow pattern of each section of the liver. 
PROXIMITY to BLOOD TOXINS: The hepatocytes nearest the center of this triangle will be closest to toxins in the blood; hepatocytes nearer the central veins (the edges) are less subject to damage from blood toxins. 
JAUNDICE: Buildup of bilirubin in blood. Indication of liver pathology. Most common causes: 
Bile duct obstruction 
Hemolytic anemia: huge overflow of heme metabolites. 
The liver itself is damaged. 
HEPATITIS-C: It is a very common risk factor for liver disease associated with Alcoholism. Something like 95% of people with Cirrhosis from Alcoholism also had Hepatitis-C infection. 
GALLBLADDER: Reservoir for concentrated bile, released under the influence of CCK. 

Gallbladder epithelium absorbs NaCl from the bile, along with water, making the bile concentrated. 
CCK: Two effects 
Gallbladder contraction (of myoepithelial cells) to squeeze out the good stuff. 
Concurrent relaxation of Sphincter of Oddi which holds in bile. 
GASTRO-ESOPHAGEAL REFLUX DISEASE (GERD): 

MAJOR CAUSE: Transient inappropriate opening of the LES. 
SYMPTOMS: 
Heartburn 
Regurgitation 
Dysphagia (difficulty swallowing) 
Odynophagia (painful swallowing) 
PEPTIC ULCER DISEASE: 

Helicobacter Pylori is responsible for 95% of duodenal ulcer diseases. 


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DEVELOPMENT
DEVELOPMENT OF THE EYE: 

EARLY DEVELOPMENT: 
OPTIC SULCI: Located on Neural Folds of the neural groove. 
OPTIC VESICLE: Will be formed from the Optic Sulci. 
INDUCTION: OPTIC VESICLE then induces then Surface Ectoderm: Surface Ectoderm ------> Primordium of Lens. 
The lens is formed from surface ectoderm -- not neuroectoderm. 
Len then buds off to form Lens Vesicle. 
CROSS-INDUCTION: THE LENS then induces a change in the Optic Vesicle: Optic Vesicle ------> Optic Cup 
OPTIC CUP: It then forms two layers which are essentially fused together. 
OUTER LAYER will become the Retinal Pigmented Epithelium 
INNER LAYER will become the Neural Retina 
HYALOID ARTERY + HYALOID VEINS: Developmental vessels will become the Central Artery and Vein of the Retina. They perfuse both the lens primordium and optic cup in development. 
OPTIC STALK: Forms from the Optic Cup. It is the primordial optic nerve, with Hyaline Vessels in the middle. 
BIRTH: Optic Nerve is fully formed but myelination is not complete. 
Complete myelination requires light stimuli and O2 from the external environment. 
DEVELOPMENT OF RETINA: 
Retinal Pigmented Epithelium forms from Outer Layer of Optic Cup 
Neural Retina forms from Inner Layer of Optic Cup. 
Inner Retinal Space: Primitive space between outer and inner layers of optic cups. Trauma can cause the space to reopen in the adult, resulting in RETINAL DETACHMENT. 
DEVELOPMENT OF LENS: It forms from Surface Ectoderm 
Tunica Vasculosa Lentis: Posterior vascular portion of lens in development, originating from Hyaloid vessels. 
PUPILLARY MEMBRANE = clinical condition resulting from developmental failure of the anterior hyaloid vessels to degenerate and retract from the lens. 
CORNEA: Both mesodermal and ectodermal. 
PUPILLARY MUSCLES: They form from neuroectoderm which quite unusual for muscle. 
EYE MALFORMATIONS: 
COLOBOMA: Keyhole life defect in eye. 
Persistence of the Choroidal Fissure during development. 
PERSISTENT PUPILLARY MEMBRANE: Maintenance of Tunica Vasculosa (anterior lens) in adult. 
Congenital Glaucoma: Can be caused by Rubella virus. 
Cataracts can be caused by Congenital Galactosemia, resulting in buildup of galactose on lens. 
EAR DEVELOPMENT: 

BRANCHIAL ARCH DERIVATIVES: 
FIRST BRANCHIAL CLEFT: External Auditory Meatus 
FIRST BRANCHIAL ARCH: Malleus and Incus 
SECOND BRANCHIAL ARCH: Stapes 
INTERNAL EAR: It is derived from surface ectoderm in the region of the hindbrain. 
Otic Placode: thickening of surface ectoderm in hindbrain region. 
Otic Vesicle form from this: It will be responsible for all structures associated with Utricle and Saccule, and Vestibular apparatus 
Dorsal Otic Vesicle ------> Utricle 
Ventral Otic Vesicle ------> Saccule 
Endolymphatic Sac will form as extension of dorsal otic vesicle 
DIVERTICULA: Also forms from Otic Vesicle. The middle of each of three diverticular will get eaten away, forming the Semicircular Canals. 
TYMPANIC MEMBRANE: It forms as a meeting together of endoderm and ectoderm: ingrowth of ectoderm and outgrowth of endoderm. 
COCHLEA: It forms. 
PINNA: The hillocks of the pinna are derived from the first two branchial arches. 
FIRST ARCH SYNDROME: Failure of the pinna hillocks to form is a sign of severe congenital abnormalities involving failure of neural crest migration. 
PRIMARY INDUCTION: The key induction in development, in which dorsal mesoderm induces ectoderm to form neural structures. 

SECONDARY INDUCTIONS: All other inductions in development. 

INSTRUCTIVE: Message-specific. The responding cell will express a specific set of gene in response to the inductive signal from the inducer. 
The optic vesicle instructively induces the lens vesicle to form the lens. Without the adjacent presence of optic vesicle, the lens will not form. 
PERMISSIVE: Non-specific. The responding cell will express the genes it was going to express anyway in the presence of the inducer. The inducer is simply required to allow the differentiation. 
INTEGRINS: Regulate interaction of cell with extracellular matrix, and mediate cellular migration through the ECM. Migrating cells will interact with laminin and fibronectin in the ECM. These interactions are essential to development. 

CELL ADHESION: Like-cells will adhere to like-cells. 

EXPTS: Mix cells of different germinal layers from different tissues. They will reassociate spontaneously into germinal layers (i.e. endoderm / mesoderm / ectoderm), regardless of the species or tissue from which they came. 
CELL ADHESION MOLECULES (CAM): Surface molecules that mediate adhesion between similar cells. 
NEURAL-CAM (N-CAM): It is highly expressed during the neural tube stage. 
NEURAL CREST MIGRATION: N-CAM expression is ceased so that neural crest cells can dissociate and migrate. 
The presence of Fibronectin, indicating a migratory path, seems to mediate this downregulation. 
When the neural cells reach destination (such as Ganglion cells), N-CAM expression is resumed. 
Again, Fibronectin absence seems to mediate this expression. 
LAMININ: It is similar to fibronectin in that it mediates cell migration. It is specific to migration of nerves. 


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Lesson 2-1
CELLS

 

2-1. THE CELLULAR LEVEL

a. The individual cell is the unit of structure of all living things. An entire organism may consist of a single cell (unicellular) or many cells (multicellular).

b. In human beings and other multicellular organisms, the cells tend to be organized in specific ways. A group of like cells performing a particular function is referred to as a tissue. An organ is a discrete structure composed of several different tissues together. An organ system is a group of organs together performing an overall function. (An example of an organ system is the digestive system.) The individual organism is the combination of all of these things as a discrete and separate entity.

c. Although all living matter is composed of cells, animal cells and plant cells are significantly different from each other. Not only do plant cells contain chlorophyll, a green coloring matter; plant cells also have a cell wall around them which is made up of a very complex carbohydrate known as cellulose. Neither chlorophyll nor a cell wall is present in connection with animal cells.

 

2-2. THE MAJOR COMPONENTS OF A "TYPICAL" ANIMAL CELL 

A "typical" animal cell is illustrated in Figure 2-1.

a. Cell Membrane. As its outer boundary, the animal cell has a special structure called the cell or plasma membrane. All of the substances that enter or leave the cell must in some way pass through this membrane.

b. Protoplasm. The major substance of the cell is known as protoplasm. It is a combination of water and a variety of materials dissolved in the water. Outside the cell nucleus (see below), protoplasm is called cytoplasm. Inside the cell nucleus, protoplasm is called nucleoplasm.

c. Organelles. Within the cytoplasm, certain structures are called organelles. These organelles include structures such as the endoplasmic reticulum, ribosomes, various kinds of vacuoles, the Golgi apparatus, mitochondria, and centrioles.

(1) The endoplasmic reticulum resembles a circulatory system for the individual cell. It is a network composed of unit (single-thickness) membranes.

 

 



 [img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0201.jpg]]
Figure 2-1. A "typical" animal cell.

(2) The ribosomes are granular particles concerned with protein synthesis. They may be found free, clustered, or attached to the endoplasmic reticulum.

(3) The vacuoles are small spaces or cavities within the cytoplasm. These serve functions at the cellular level such as digestion, respiration, excretion, and storage.

(4) The Golgi complex is a portion of the endoplasmic reticulum that aids in the final preparation of certain proteins and mucus-like substances and in the movement of these substances. It is best-developed in secretory cells.

(5) The mitochondria are the "powerhouses" of the cell. They "recharge" ADP molecules to form ATP molecules.

(6) There are ordinarily two centrioles. These organelles play a major role in cell division.

 d. Nucleus. Within the cell is the nucleus. This structure has a nuclear membrane separating it from the cytoplasm. Within the nucleus is the chromatin material, made up of the protein deoxyribonucleic acid (DNA). At the time of cell division, this chromatin material is aggregated into individual structures known as chromosomes. Each chromosome has a set of specific genes, which determine all of the physical and chemical characteristics of the body, which represent its structure and function.

 

2-3. ENERGY

a. We mentioned in lesson 1 that the human body depended upon external sources for energy. Plants use solar radiation to make glucose and other nutrients. The human body takes glucose and other nutrients directly or indirectly from plants. The body receives oxygen from the air. The energy that was once derived by plants from solar radiation is released within human cells by the process of metabolic oxidation. This involves the combination of glucose and other nutrients with oxygen, releasing the stored energy.

b. The mitochondria of the cells use this released energy to form ATP molecules from ADP molecules. Adenosine diphosphate is converted to ATP by the addition of a "part of a molecule" called a phosphate radical. The binding of this phosphate radical requires a large quantity of energy, which can be released later when the phosphate radical is separated off. Adenosine triphosphate provides energy for cellular processes such as active transport of substances across membranes, synthesis of chemical compounds for the body, and mechanical work (such as muscle contraction). When an Adenosine triphosphate molecule provides energy for such a process, it loses a phosphate radical and becomes ADP. Then, the cycle begins again as ADP is converted into ATP within the mitochondria.

c. Certain cells, such as muscle cells and nerve cells, require great amounts of energy. Such cells have well-developed mitochondria.
What does complex mean?
 Lesson 3
COSTAL ("THORACIC") BREATHING

7-10. DEFINITION

Costal breathing is breathing accomplished by moving of the rib cage as a whole. 

7-11. ANATOMY OF THE HUMAN RIB CAGE

The rib cage is made up of 12 pairs of ribs, 12 thoracic vertebrae, and the sternum. 

Ribs. 
(1)  Structure of a "typical" rib. Each rib is a flat-type bone that is curved laterally. Along its inferior margin is a subcostal groove. 
(2)  Attachments. 
(a) All 12 pairs of ribs are attached posteriorly to the thoracic vertebrae.
(b)Anteriorly, the upper 10 pairs of ribs are attached directly or indirectly to the sternum. The indirect attachments are made through costal cartilages to the ribs above.
(c) It is important to note that both the posterior and anterior articulations are located essentially in the midline of the body, back and front.

(3) Costal cartilages. The costal cartilages are bars of cartilage of varying lengths. Since costal cartilages are elastic, they can be twisted (deformed) and returned to their original shape.

Sternum. . The sternum is located in the midline anteriorly, immediately beneath the skin. (Since the sternum is a flat bone with hematopoietic (blood-forming) red marrow and is so close to the surface of the body, it is a convenient location for taking a sample of hematopoietic tissue for clinical examination--the sternal punch.) 
(1) The sternum is made up of three parts--the manubrium above, the body as the main portion, and the xiphoid process below. 
(2) Where the manubrium articulates with the top of the body of the sternum is a sternal angle (Louis' angle). The sternal angle is important in costal breathing, since it allows for greater expansion of the rib cage. (In the clinic, the sternal angle is important as a landmark. It marks the site of the second rib and is used to identify locations on the chest wall.) 
Thoracic Vertebrae. Posteriorly, there are 12 thoracic vertebrae, joined by intervertebral discs. Their curvature, the thoracic curvature, is concave anteriorly. During breathing, this curvature straightens and thus increases the expansion of the rib cage. 
Segmentation. The segmentation of the thorax is produced by both the intervertebral discs and the intercostal spaces between adjacent ribs. Such segmentation of the rib cage allows motion to take place, especially bending to the right or left. 
Intercostal Muscles. The intercostal spaces are filled by two layers of intercostal muscles. The intercostal muscles extend from the vertebrae behind to the sternum in front. A strengthening "plywood effect" is created by the arrangement of the two layers at a right angle to each other. Therefore, these muscles help to maintain the "solid-wall" condition of the thorax. For this reason, a pressure gradient can be maintained between the inside and outside of the thorax. 
Skeletal Muscles Attached to the Rib Cage. Various skeletal muscles are attached to the rib cage. Some extend from above and draw the rib cage upward. Others extend from below and draw the cage downward. 
7-12. COSTAL INHALATION

In costal inhalation, the lungs are expanded and inflated with air because of upward movement of the rib cage. The expansion of the rib cage is sufficient to allow the needed volume of air to enter the lungs. There are two different types of movements of the ribs that produce this expansion of the rib cage. 

One type of movement involves the so-called "bucket handle" effect. As each rib swings upon its ends, like a bucket handle swinging up from the sides of the bucket, the rib moves upward and outward laterally. As this type of movement occurs on both sides of the rib cage, the transverse diameter of the rib cage increases from side to side. 
The second type of movement is described as follows: The lowest points of the ribs are their front ends at the sternum. During inhalation, these front ends move upward and forward along with the sternum. This increases the diameter of the thoracic cavity from front to back (anterior-posterior (A-P) diameter). 
The increases in the transverse and A-P diameters enlarge the volume of the thoracic cavity and thus decrease the pressure of the air inside (Boyle's law). Thus, there is a relatively higher atmospheric pressure outside. This pushes air into the respiratory passageways and into the alveoli of the lungs. The alveoli are inflated by this inflowing air. 
7-13. COSTAL EXHALATION 

The lungs empty during costal exhalation, a process that is essentially the reverse of costal inhalation. The rib cage moves downward as a whole. 
(1)        In small-volume exchanges, the costal cartilages are sufficiently resilient (elastic or springy) to pull the rib cage downward. 
(2)        With greater-volume exchanges, musculature can be recruited to aid in lowering the rib cage. 
(3)        Gravity may also play a role. 
As the transverse and A-P diameters decrease, the volume of the thoracic cavity also decreases. This increases the pressure of the air inside (Boyle's law). Thus, there is a relatively lower atmospheric pressure outside, and air is forced out of the lungs. (The elasticity (springiness) of tissues within the thoracic cavity also helps to push the air out.) 
 
n many ways, the cell body is similar to other types of cells. It has a nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles. It lacks centrioles, however. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell
http://mysite.verizon.net/vzepz6a9/biorefweb/cells.html

Cells and Cellular Processes
 
Animal and plant cells 

CELL - Smallest living unit of which all organisms are composed 

Cell structures and functions 

structure
 main functions
 present in animal or plant cell or both
 
centriole (1) aids in cell reproduction animal cells 
vacuole(2) storage both 
lysosomes (3) contain enzymes, break down old worn out cell parts animal cells 
mitochondria (4) cellular respiration { makes energy (ATP) } both 
cytoplasm (5) site of most metabolism, Jelly like substance both 
golgi complex (6) packaging of proteins both 
nucleolus (7) production of ribosomes, contains RNA both 
nucleus (8) control; heredity: contains DNA in chromosomes (9) both 
ribosome (10) protein synthesis both 
endoplasmic reticulum (11) transport of proteins throughout cell both 
cell wall (12) support; protection; made of cellulose plant cells 
cell membrane (13) boundary "gate keeper" regulates entry and exit of materials: semipermeable both 
chloroplast (14) site of photosynthesis, contains chlorophyll plant cells 

Animal Cell 

 

Plant Cell 

 

cells drawn by Heather Ott 

What are the major differences between a plant and animal cell? 

1. animal cells don't have any chloroplasts and plant cells do. 

2. plant cells don't have any centrioles and animal cells do. 

3. plant cells have few large vacuoles, animal cells have many small vacuoles. 

4. plant cells have a cell wall and animal cells don't. 

What type of environments are cells found in? 

aqueous (water based) 

What are some special structures involved with cellular locomotion? 

1. pseudopodia (false feet)- like throwing a grappling hook and pulling yourself along, accomplished by cytoplasmic streaming. 

  

2. cilia- tiny beating hairs that act like oars 

  

3. flagella- whip like tail (sperm cell) 

 

illustrations drawn by Jennifer Olivio 


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Cell Theory: 

1. cells are the unit of structure of life, all living things are made of cells. 

2. cells are the unit of function of life 

3. cells come from other cells 

exceptions to the cell theory 

a. viruses- perform all the life functions, but they are not cells. 

b. mitochondria and chloroplasts- can reproduce on their own 


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Cellular Processes 

Cellular transport 

-movement of materials (nutrients and wastes) into, throughout, and out of cells 

1. Active TransPort- transport that requires "energy,"(ATP) "movement that is up hill" 

movement from an area of low concentration to an area of higher conc. 

2. passive transport- transport that does not require energy," movement that is down hill". 

movement from an area of higher conc. to an area of lower conc. 

Types of passive transport 

diffusion- passive transport 

osmosis- passive transport of water 

 



 

 

Cellular Respiration- 

The production of ATP (energy)*NOT BREATHING (GAS EXCHANGE)* 

Two types of respiration 

1. Anaerobic respiration - The production of ATP without the use of oxygen 

glucose --->Lactic Acid + 2ATP (bacteria) 

glucose --->Alcohol + Carbon Dioxide + 2ATP (Yeast) 

2.Aerobic Respiration- 

the production of ATP utilizing oxygen 

Glucose + oxygen----->6 carbon dioxide + 6 water + 36 ATP 

true equation 

1.Anaerobic phase - 

glucose ----> pyruvic acid + 2ATP 

2. Aerobic phase- 

pyruvic acid + oxygen -----> 6 carbon dioxide + 6 water + 34 ATP 

  

RESPIRATION OCCURS IN THE MITOCHONDRIA  

TO HAVE RESPIRATION OCCUR IT INVOLVES THE DIGESTIVE SYSTEM, GAS EXCHANGE (RESPIRATORY ) SYSTEM, AND THE CIRCULATORY SYSTEM. 
  

How do we get energy from ATP 

By hydrolysis: 

ATP + H2O------ATP-ase------->ADP + P + energy.  

This occurs in the cytoplasm of cells 

Photosynthesis 
The process by which glucose is produced from carbon dioxide and water by plants and other photosynthetic organisms 

equation: 

H2O+ CO2 ------sunlight----> glucose + O2 

Building processes (biochemistry) 

Organic Compounds (nutrients) and their building blocks 

1. Protein - Amino acids 

2. Lipid - Fatty acids + Glycerol 

3. Carbohydrates - monosaccharides 

  

What each Organic Compound (nutrient) is needed for 

Carbohydrates are needed to produce energy 
lipids are needed to make lipids(fats) which help to protect body tissue, cushioning, insulation, energy storage and production 
Proteins are needed to make muscle(protein) 
"put it together" 

1. Dehydration Synthesis - Making a larger compound from smaller building blocks through the loss of water  

building block + building block -----> compound + water 

This is represented by an equation: 

Amino Acid + Amino Acid ---> Protein + water 

Monosacc. + Monosacc.---> Carbos. + water 

Fatty Acids + Glycerol ---> Lipids + water 

"take it apart"  

2. Hydrolysis - Breaking apart a larger compound into it's building blocks through the addition of water 

 compound + water ----- > building block + building block 

This is represented by an equation: 

Protein + water ----> Amino Acids 

Carbohydrate + water ---> Monosacc. 

Lipid + water --> Fatty Acids+Glycerol 

These processes are allowed to occur at body conditions by ENZYMES AND COENEZYMES (VITAMINS) 

These enzymes are shown in the equation by writing the word "enzymes" or the name of the enzyme used above the arrow:  

Protein + water -----enzymes-----> Amino Acids 

to name an enzyme drop the ending of the organic compound being dealt with and add the ending "ase" 

ex. fructose 

fructose -ose  = fruct +ase = fructase 

 



 


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Cellular Reproduction

Reproduction is the process in which new organisms of the same species are produced 

 

-MITOTIC CELL DIVISION - 

a process where the nuclear material of a cell reproduces and divides, then the cytoplasm of the cell divides creating two genetically identical daughter cells with the same number of chromosomes as the parent cell. 

 

Steps in mitosis 

interphase - the stage where a cell grows in size and performs all normal cell activities 

prophase - nuclear membrane disappears, chromatids become visible, centrioles start to migrate, spindle fibers start to form 

metaphase - chromatids align along the equator, centrioles are at the poles 

anaphase - chromatids are pulled apart by spindle fibers and start to move towards the poles 

telophase - chromosomes are each pole, nuclear membrane reforms and the cell starts to "pinch in" 

Cytokinesis now occurs and divides the cytoplasm creating two new genetically identical cells 

*Cancer is uncontrolled cellular reproduction 

 

Gamete(sex cell) production is accomplished by Meiosis. All gametes produced have ONE HALF the original chromosome number 

 

Two specific types of meiosis are Oogenesis and Spermatogenesis. 

Spermatogenesis - produces four sperm cells from one primary sex cell (parent cell) 

Oogenesis - produce one egg cell and three polar bodies from one primary sex cell ( parent),  Polar bodies generally become food for a developing embryo (ex. yolk of egg) 

DIFFERENCES BETWEEN MITOSIS AND MEIOSIS 

1. Mitosis produces daughter cells with a full set of chromosomes equal in number to that of the parent, whereas meiosis produces gametes with one half the chromosome number of the primary sex cell(parent) 

2. Meiosis would take place in ovaries or testes, whereas mitosis occurs in all body tissues( growth is a result of mitosis) 

Both Mitosis and Meiosis rely upon DNA Replication 


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HOMEWORK:

Cell unit homework

 


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LABS:

Investigating cells and cell structures lab - Food poisioning lab - Tissue comparison lab


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Related Links: 

dictionary of cell biology / www Cell Biology Course / Virtual Cell / Cells Alive 

Photosynthesis / Photosynthesis directory 


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Connective tissues bind structures together, form a framework and support for organs and the body as a whole, store fat, transport substances, protect against disease, and help repair tissue damage. They occur throughout the body. Connective tissues are characterized by an abundance of intercellular matrix with relatively few cells. Connective tissue cells are able to reproduce but not as rapidly as epithelial cells. Most connective tissues have a good blood supply but some do not. 


 

Numerous cell types are found in connective tissue. Three of the most common are the fibroblast, macrophage, and mast cell. The types of connective tissue include loose connective tissue, adipose tissue, dense fibrous connective tissue, elastic connective tissue, cartilage, osseous tissue (bone), and blood.

 
Muscle tissue is composed of cells that have the special ability to shorten or contract in order to produce movement of the body parts. 
Cellular respiration
From Wikipedia, the free encyclopedia
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Cellular respiration describes the metabolic reactions and processes that take place in a cell or across the cell membrane to obtain biochemical energy from fuel molecules and the release of the cells' waste products. Energy is released by the oxidation of fuel molecules and is stored as "high-energy" carriers. The reactions involved in respiration are catabolic reactions in metabolism.

Fuel molecules commonly used by cells in respiration include glucose, amino acids and fatty acids, and a common oxidizing agent (electron acceptor) is molecular oxygen (O2). There are organisms, however, that can respire using other organic molecules as electron acceptors instead of oxygen. Organisms that use oxygen as a final electron acceptor in respiration are described as aerobic, while those that do not are referred to as anaerobic.

The energy released in respiration is used to synthesize molecules that act as a chemical storage of this energy. One of the most widely used compounds in a cell is adenosine triphosphate (ATP) and its stored chemical energy can be used for many processes requiring energy, including biosynthesis, locomotion or transportation of molecules across cell membranes. Because of its ubiquitous nature, ATP is also known as the "universal energy currency", since the amount of it in a cell indicates how much energy is available for energy-consuming processes.

Contents [hide]
1 Aerobic respiration 
1.1 Glycolysis 
1.2 Oxidative decarboxylation of pyruvate 
1.3 Citric Acid cycle/Krebs cycle 
1.4 Oxidative phosphorylation 
2 Theoretical yields 
3 Anaerobic respiration 
4 See also 
5 References 
6 External links 
 


[edit] Aerobic respiration
Aerobic respiration requires oxygen in order to generate energy (ATP). It is the preferred method of pyruvate breakdown from glycolysis and requires that pyruvate enter the mitochondrion to be fully oxidized by the Krebs cycle. The product of this process is energy in the form of ATP (Adenosine Triphosphate), by substrate-level phosphorylation, NADH and FADH2.

Simplified Reaction: C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l) ΔHc -2880 kJ

The reducing potential of NADH and FADH2 is converted to more ATP through an electron transport chain with oxygen as the "terminal electron acceptor". Most of the ATP produced by aerobic cellular respiration is made by oxidative phosphorylation. This works by the energy released in the consumption of pyruvate being used to create a chemiosmotic potential by pumping protons across a membrane. This potential is then used to drive ATP synthase and produce ATP from ADP. Biology text books often say that between 36-38 ATP molecules can be made per oxidised glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 32-34 from the electron transport system). However, this maximum yield is never quite reached due to losses (leaky membranes) as well as the cost of moving pyruvate and ADP into the mitochondrial matrix.

Aerobic metabolism is more efficient than anaerobic metabolism (which yields 2 mol ATP per 1 mol glucose). They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation. The post glycolytic reactions take place in the mitochondria in eukaryotic cells, and in the cytoplasm in prokaryotic cells.


[edit] Glycolysis
Main article: Glycolysis
Glycolysis is a metabolic pathway that is found in the cytoplasm of cells in all living organisms and does not require oxygen. The process converts one molecule of glucose into two molecules of pyruvate, and makes energy in the form of two net molecules of ATP. Four molecules of ATP per glucose are actually produced; however, two are consumed for the preparatory phase. The initial phosphorylation of glucose is required to destabilize the molecule for cleavage into two triose sugars. During the pay-off phase of glycolysis four phosphate groups are transferred to ADP by substrate-level phosphorylation to make four ATP and two NADH are produced when the triose sugars are oxidized. Glycolysis takes place in the cytoplasm of the cell. The overall reaction can be expressed this way:

Glucose + 2 ATP + 2 NAD+ + 2 Pi + 4 ADP → 2 pyruvate + 2 ADP + 2 NADH + 4 ATP + 2 H2O 

[edit] Oxidative decarboxylation of pyruvate
Main article: Pyruvate decarboxylation
The pyruvate produced in glycolysis is transported across the mitochondrial membranes by a membrane transport protein called the pyruvate carrier.[1] The pyruvate decarboxylase then produces acetyl-CoA from pyruvate inside the mitochondrial matrix. This oxidation reaction also releases carbon dioxide as a product. In the process one molecule of NADH is formed per pyruvate oxidized.


[edit] Citric Acid cycle/Krebs cycle
Main article: Citric acid cycle
When oxygen is present, acetyl-CoA is produced from pyruvate. If oxygen is not present the cell undergoes fermentation of the pyruvate molecule. If acetyl-CoA is produced the molecule then enters the citric acid cycle (Krebs cycle) inside the mitochondrial matrix, and gets oxidized to CO2 while at the same time reducing NAD to NADH. NADH can be used by the electron transport chain to create further ATP as part of oxidative phosphorylation. To fully oxidize the equivalent of one glucose molecule two acetyl-CoA must be metabolized by the Krebs cycle. Two waste products, H2O and CO2 are created during this cycle.


[edit] Oxidative phosphorylation
Main articles: Oxidative phosphorylation, Electron transport chain, Electrochemical gradient, and ATP synthase
In eukaryotes, oxidative phosphorylation occurs in the mitochondrial cristae. It comprises the electron transport chain that establishes a proton gradient (chemiosmotic potential) across the inner membrane by oxidizing the NADH produced from the Krebs cycle. ATP is synthesised by the ATP synthase enzyme when the chemiosmotic gradient is used to drive the phosphorylation of ADP.


[edit] Theoretical yields
The yields in the table below are for one glucose molecule being fully oxidized into carbon dioxide. It is assumed that all the reduced coenzymes are oxidized by the electron transport chain and used for oxidative phosphorylation.

Step coenzyme yield ATP yield Source of ATP 
Glycolysis preparatory phase  -2 Phosphorylation of glucose and fructose 6-phosphate uses two ATP from the cytoplasm. 
Glycolysis pay-off phase  4 Substrate-level phosphorylation 
2 NADH 4 (6) Oxidative phosphorylation. Only 2 ATP per NADH since the coenzyme must feed into the electron transport chain from the cytoplasm rather than the mitochondrial matrix. If the malate shuttle is used to move NADH into the mitochondria this might count as 3 ATP per NADH. 
Oxidative decarboxylation 2 NADH 6 Oxidative phosphorylation 
Krebs cycle  2 Substrate-level phosphorylation 
6 NADH 18 Oxidative phosphorylation 
2 FADH2 4 Oxidative phosphorylation 
Total yield 36 (38) ATP From the complete oxidation of one glucose molecule to carbon dioxide and oxidation of all the reduced coenzymes. 

Although there is a theoretical yield of 36-38 ATP molecules per glucose during cellular respiration, such conditions are generally not realized due to losses such as the cost of moving pyruvate (from glycolysis), phosphate and ADP (substrates for ATP synthesis) into the mitochondria. All are actively transported using carriers that utilise the stored energy in the proton electrochemical gradient.

The pyruvate carrier is a symporter and the driving force for moving pyruvate into the mitochondria is the movement of protons from the intermembrane space to the matrix. 
The phosphate carrier is an antiporter and the driving force for moving phosphate ions into the mitochondria is the movement of hydroxyls ions from the matrix to the intermembrane space. 
The adenine nucleotide carrier is an antiporter and exchanges ADP and ATP across the inner membrane. The driving force is due to the ATP (-4) having a more negative charge than the ADP (-3) and thus it dissipates some of the electrical component of the proton electrochemical gradient. 
The outcome of these transport processes using the proton electrochemical gradient is that more than 3 H+ are needed to make 1 ATP. Obviously this reduces the theoretical efficiency of the whole process and the likely maximum is closer to 28-30 ATP molecules.[2] In practice the efficiency may be even lower due to the inner membrane of the mitochondria being slightly leaky to protons.[3] Other factors may also dissipate the proton gradient creating an apparently leaky mitochondria. An uncoupling protein known as thermogenin is expressed in some cell types and is a channel that can transport protons. When this protein is active in the inner membrane it short circuits the coupling between the electron transport chain and ATP synthesis. The potential energy from the proton gradient is not used to make ATP but generates heat. This is particularly important in a baby's brown fat, for thermogenesis, and hibernating animals.


[edit] Anaerobic respiration
Main article: Anaerobic respiration 
Without oxygen, pyruvate is not metabolized by cellular respiration but undergoes a process of fermentation. The pyruvate is not transported into the mitochondrion, but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. This serves the purpose of oxidizing the hydrogen carriers so that they can perform glycolysis again and removing the excess pyruvate. This waste product varies depending on the organism. In skeletal muscles, the waste product is lactic acid. This type of fermentation is called lactic acid fermentation. In yeast, the waste products are ethanol and carbon dioxide. This type of fermentation is known as alcoholic or ethanol fermentation.

Anaerobic respiration is less efficient at using the energy from glucose since 2 ATP are produced during anaerobic respiration per glucose, compared to the 30 ATP per glucose produced by aerobic respiration. This is because the waste products of anaerobic respiration still contain plenty of energy. Ethanol, for example, can be used in gasoline (petrol) solutions. Glycolytic ATP, however, is created more quickly. For prokaryotes to continue a rapid growth rate when they are shifted from an aerobic environment to an anaerobic environment, they must increase the rate of the glycolytic reactions. Thus, during short bursts of strenuous activity, muscle cells use anaerobic respiration to supplement the ATP production from the slower aerobic respiration, so anaerobic respiration may be used by a cell even before the oxygen levels are depleted, as is the case in sports that do not require athletes to pace themselves, such as sprinting.


[edit] See also
Tetrazolium chloride: cellular respiration indicator 

[edit] References
^ Sugden MC, Holness MJ (2003). "Trials, tribulations and finally, a transporter: the identification of the mitochondrial pyruvate transporter". Biochem. J. 374 (Pt 3): e1–2. PMID 12954079.  
^ Rich PR (2003). "The molecular machinery of Keilin's respiratory chain". Biochem. Soc. Trans. 31 (Pt 6): 1095-105. PMID 14641005.  
^ Porter RK, Brand MD (1995). "Mitochondrial proton conductance and H+/O ratio are independent of electron transport rate in isolated hepatocytes". Biochem. J. 310 ( Pt 2): 379-82. PMID 7654171.  
[hide]v • d • eMetabolism 
Catabolism - Anabolism 
Metabolic pathway - Metabolic network - Cellular respiration (Anaerobic/Aerobic)

Protein metabolism - Carbohydrate metabolism - Lipid metabolism - Iron metabolism 


[edit] External links
Chart of Important Metabolic Products 
A detailed description of respiration vs. fermentation 
Kimball's online resource to cellular respiration 
Cellular Respiration and Fermentation at Clermont College 
Retrieved from "http://en.wikipedia.org/wiki/Cellular_respiration"
Categories: Cellular respiration | Metabolism | Plant physiology
Cellular Respiration Vocabulary Quiz
1.	Cellular Respiration
2.	ATP
3.	ADP
4.	Oxidation
5.	Reduction
6.	Reaction
7.	Aerobic Respiration
8.	Anaerobic Respiration
9.	Glycolysis
10.	Fermentation
11.	Acetyl Co A
12.	Krebs Cycle
13.	Electron Transport Chain
Cellular Respiration Vocabulary Quiz
1.	[[Cellular Respiration]]
2.	[[ATP]]
3.	[[ADP]]
4.	[[Oxidation]]
5.	[[Reduction]]
6.	[[Reaction]]
7.	[[Aerobic Respiration]]
8.	[[Anaerobic Respiration]]
9.	[[Glycolysis]]
10.	[[Fermentation]]
11.	[[Acetyl Co A]]
12.	[[Krebs Cycle]]
13.	[[Electron Transport Chain]]
Central Nervous System

The brain is located within the cranial cavity of the skull and consists of the cerebral hemispheres (forebrain), diencephalon, brain stem structures, and cerebellum (Figure 7.7). 

The two cerebral hemispheres form the largest part of the brain. Their surface, or cortex, is gray matter and their interior is white matter. The cortex is convoluted and has gyri, suici, and fissures. The cerebral hemispheres are involved in logical reasoning, moral conduct, emotional responses, sensory interpretation, and the initiation of voluntary muscle activity. Several functional areas of the cerebral lobes have been identified. The basal nuclei, regions of gray matter deep within the white matter of the cerebral hemispheres, modify voluntary motor activity. Parkinson's disease and Huntington's chorea are disorders of the basal nuclei. 

The diencephalon is superior to the brain stem and is enclosed by the cerebral hemispheres. The major structures include the following: 

The thalamus encloses the third ventricle and is the relay station for sensory impulses passing to the sensory cortex for interpretation. 

The hypothalamus makes up the "floor" of the third ventricle and is the most important regulatory center of the autonomic nervous system (regulates water balance, metabolism, thirst, temperature, and the like). 

The epithalamus includes the pineal body (an endocrine gland) and the choroid plexus of the third ventricle. 

The brain stem is the short region inferior to the hypothalamus that merges with the spinal cord. 

The midbrain is most superior and is primarily fiber tracts. 

The pons is inferior to the midbrain and has fiber tracts and nuclei involved in respiration. 

The medulla oblongata is the most inferior part of the brain stem. In addition to fiber tracts, it contains autonomic nuclei involved in the regulation of vital life activities (breathing, heart rate, blood pressure, etc.). 

The cerebellum is a large, cauliflower-like part of the brain posterior to the fourth ventricle. It coordinates muscle activity and body balance. 
Return to top 



Protection of the CNS 

Bones of the skull and vertebral column are the most external protective structures. 

Meninges are three connective tissue membranes: dura mater (tough outermost), arachnoid mater (middle weblike), and pia mater (innermost delicate) (Figure 7.8). The meninges extend beyond the end of the spinal cord. 

Cerebrospinal fluid (CSF) provides a watery cushion around the brain and cord. CSF is formed by the choroid plexuses of the brain. It is found in the subarachnoid space, ventricles, and central canal (Figure 7.9). CSF is continually formed and drained. 

The blood-brain barrier is composed of relatively impermeable capillaries. 

Brain dysfunctions 

Head trauma may cause concussions (reversible damage) or contusions (nonreversible damage). When the brain stem is affected, unconsciousness (temporary or permanent) occurs. Trauma-induced brain injuries may be aggravated by intracranial hemorrhage or cerebral edema, both of which compress brain tissue- 

Cerebrovascular accidents (CVAs, or strokes) result when blood circulation to brain neurons is blocked and brain tissue dies. The result may be visual impairment, paralysis, and aphasias. 

Alzheimer's disease is a degenerative brain disease in which abnormal protein deposits and other structural changes appear. It results in slow, progressive loss of memory and motor control plus increasing dementia. 

Techniques used to diagnose brain dysfunctions include the EEG, simple reflex tests, pneumo-encephalography, angiography, and CT, PET, and MRI scans. 

The spinal cord is a reflex center and conduction pathway. Found within the vertebral canal, the cord extends from the foramen magnum to L1 or L2. The cord has a central bat-shaped area of gray matter surrounded by columns of white matter, which carry motor and sensory tracts from and to the brain. 
Protection of the CNS 

Bones of the skull and vertebral column are the most external protective structures. 

Meninges are three connective tissue membranes: dura mater (tough outermost), arachnoid mater (middle weblike), and pia mater (innermost delicate) (Figure 7.8). The meninges extend beyond the end of the spinal cord. 

Cerebrospinal fluid (CSF) provides a watery cushion around the brain and cord. CSF is formed by the choroid plexuses of the brain. It is found in the subarachnoid space, ventricles, and central canal (Figure 7.9). CSF is continually formed and drained. 

The blood-brain barrier is composed of relatively impermeable capillaries. 

Brain dysfunctions 

Head trauma may cause concussions (reversible damage) or contusions (nonreversible damage). When the brain stem is affected, unconsciousness (temporary or permanent) occurs. Trauma-induced brain injuries may be aggravated by intracranial hemorrhage or cerebral edema, both of which compress brain tissue- 

Cerebrovascular accidents (CVAs, or strokes) result when blood circulation to brain neurons is blocked and brain tissue dies. The result may be visual impairment, paralysis, and aphasias. 

Alzheimer's disease is a degenerative brain disease in which abnormal protein deposits and other structural changes appear. It results in slow, progressive loss of memory and motor control plus increasing dementia. 

Techniques used to diagnose brain dysfunctions include the EEG, simple reflex tests, pneumo-encephalography, angiography, and CT, PET, and MRI scans. 

The spinal cord is a reflex center and conduction pathway. Found within the vertebral canal, the cord extends from the foramen magnum to L1 or L2. The cord has a central bat-shaped area of gray matter surrounded by columns of white matter, which carry motor and sensory tracts from and to the brain. 
[img[http://upload.wikimedia.org/wikipedia/commons/2/2b/Illu_cerebrum_lobes.jpg]]
http://en.wikipedia.org/wiki/Connective_tissue

Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue.) It is largely a category of exclusion rather than one with a precise definition, but all or most tissues in this category are similarly:

Involved in structure and support. 
Derived from mesoderm, usually. 
Characterized largely by the traits of non-living tissue. 
Blood, cartilage, and bone are usually considered connective tissue, but because they differ so substantially from the other tissues in this class, the phrase "connective tissue proper" is commonly used to exclude those three. There is also variation in the classification of embryonic connective tissues; on this page they will be treated as a third and separate category.

When heated to 190 degrees Fahrenheit, connective tissue emits a "Vinegar Like Stench"[citation needed].

Contents [hide]
1 Classification 
1.1 Connective tissue proper 
1.2 Specialized connective tissues 
1.3 Embryonic connective tissues 
2 Fiber types 
3 Disorders of connective tissue 
4 Staining of connective tissue 
5 See also 
6 External links 
 


[edit] Classification

[edit] Connective tissue proper
 
Connective tissue properAreolar (or loose) connective tissue holds organs and epithelia in place, and has a variety of proteinaceous fibres, including collagen and elastin. 
Dense connective tissue (or, less commonly, fibrous connective tissue) forms ligaments and tendons. Its densely packed collagen fibers have great tensile strength. 

[edit] Specialized connective tissues
 
Specialized connective tissuesBlood functions in transport. Its extracellular matrix is blood plasma, which transports dissolved nutrients, hormones, and carbon dioxide in the form of bicarbonate. The main cellular component is red blood cells. 
Bone makes up virtually the entire skeleton in adult vertebrates. 
Cartilage makes up virtually the entire skeleton in chondrichthyes. In most other vertebrates, it is found primarily in joints, where it provides cushioning. The extracellular matrix of cartilage is composed primarily of collagen. 
Adipose tissue contains adipocytes, used for cushioning, thermal insulation, lubrication (primarily in the pericardium) and energy storage. [fat] 
Reticular connective tissue is a network of reticular fibres (fine collagen, type III) that form a soft skeleton to support the lymphoid organs (lymph nodes, bone marrow, and spleen.) 

[edit] Embryonic connective tissues
Mesenchymal connective tissue 
Mucous connective tissue 

[edit] Fiber types
Fiber types as follows:

collagenous fibers 
elastic fibers 
reticular fibers 

[edit] Disorders of connective tissue
Various connective tissue conditions have been identified; these can be both inherited and environmental.

Marfan syndrome - a genetic disease causing abnormal fibrillin. 
Scurvy - caused by a dietary deficiency in vitamin C, leading to abnormal collagen. 
Ehlers-Danlos syndrome - deficient type III collagen- a genetic disease causing progressive deterioration of collagens, with different EDS types affecting different sites in the body, such as joints, heart valves, organ walls, arterial walls, etc. 
Loeys-Dietz syndrome - a genetic disease related to Marfan syndrome, with an emphasis on vascular deterioration. 
Pseudoxanthoma elasticum - an autosomal recessive hereditary disease, caused by calcification and fragmentation of elastic fibres, affecting the skin, the eyes and the cardiovascular system. 
Systemic lupus erythematosus - a chronic, multisystem, inflammatory disorder of probable autoimmune etiology, occurring predominantly in young women. 
Osteogenesis imperfecta (brittle bone disease) - caused by insufficient production of good quality collagen to produce healthy, strong bones. 
Fibrodysplasia ossificans progressiva - disease of the connective tissue, caused by a defective gene which turns connective tissue into bone. 
Spontaneous pneumothorax - collapsed lung, believed to be related to subtle abnormalities in connective tissue. 
Sarcoma - a neoplastic process originating within connective tissue. 

[edit] Staining of connective tissue
For microscopic viewing, the majority of the connective tissue staining techniques color tissue fibers in contrasting shades. Collagen may be differentially stained by any of the following techniques:

Van Gieson's stain 
Masson's Trichrome stain 
Mallory's Aniline Blue stain 
Azocarmine stain 
Krajian's Aniline Blue stain 

[edit] See also
Zootomy 

[edit] External links
connective+tissue at eMedicine Dictionary 
t_12/12810256 at Dorland's Medical Dictionary 
Overview at kumc.edu 
UIUC Histology Subject 230 
Connective tissue atlas at uiowa.edu 
[show]v • d • eBiological tissue 
Animals Epithelium - Connective - Muscular - Nervous 
Plants Dermal - Vascular - Ground 
[show]v • d • eHistology: connective tissue 
http://en.wikipedia.org/wiki/Connective_tissue
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5119523329589723250"><img src="http://lh6.google.com/cardwell.bob/RwwzWAeFQHI/AAAAAAAABY4/TyS8auOZ2H8/s400/bonemade.gif.jpg" /></a></html>
 Lesson 3
DEFINITION AND TYPES OF BONES

4-6. DEFINITION

Bones are those individual organs that are elements of the skeletal system. 

4-7. TYPES

The individual bones of the skeleton can be categorized into three major groups according to their general shapes: 

a.      Long. 
b.      Flat. 
c.      Irregular. 
 Lesson 7
DEFINITION AND TYPES OF JOINTS

4-15. INTRODUCTION

a.      Where two bones meet each other, this junction is referred to as a joint or articulation.

b.      The joints of the human skeleton may be characterized, in general, in three different ways.

4-16. MATERIAL HOLDING JOINT TOGETHER

First, they are characterized by the type of material that holds the bones together at the joint.

a.        If the bones are fused together with bony tissue, the articulation is called a synosteosis.

b.        Thus, in a synchondrosis, the bones are held together by cartilage tissue.

c.         In a syndesmosis, the bones are held together by FCT.

NOTE: A synovial articulation is somewhat different and will be described in detail in the next section.

4-17. RELATIVE MOBILITY

A second way of categorizing joints of the human skeleton is according to relative mobility.

a.      The junctions of some bones are nonmobile, such as a synosteosis.

b.      Others are semimobile, as seen with some syndesmoses.

c.      Being structured to facilitate motion, synovial articulations (see the next section) are mobile to various degrees.

4-18. DEGREES OF FREEDOM

The term degrees of freedom refers to the number of planes in which movement is permitted. This also equals the number of axes around which motion can take place at a particular joint.

a.        One Degree of Freedom. One degree of freedom means that the joint is uniaxial. Motion can take place in a single plane around one axis only. An example is a "hinge" joint.

b.        Two Degrees of Freedom. Two degrees of freedom mean that the joint is biaxial. Motion can take place around two different axes.

c.         Three Degrees of Freedom. With three degrees of freedom, we say that the joint is multiaxial. Motion can take place around the three axes in all three planes. An example is "ball and socket" type joints.
 
 Lesson 4
DIAPHRAGMATIC ("ABDOMINAL") BREATHING

7-14. PHYSICAL CHARACTERISTICS OF THE ABDOMINOPELVIC CAVITY 

The abdominopelvic cavity is a closed system filled with a fluid (water) continuum. 
The abdominopelvic cavity is inclosed by essentially muscular barriers. 
(1)  The inferior end is closed off by the pelvic diaphragm. 
(2)  The cylindrical walls of the abdomen are composed of three muscular sheets. Their orientation is similar to plywood. These muscles are kept taut by their intrinsic tone, but they are capable of additional contraction. 
(3)  Forming the top of the abdominopelvic cavity is the thoracic diaphragm. We discuss the thoracic diaphragm in the next paragraph. 
7-15. THORACIC DIAPHRAGM

The thoracic diaphragm is attached to the inferior margin of the rib cage and to the bodies of the lumbar vertebrae behind. As a muscular membrane, it domes upward into the thoracic cavity. Upon contraction, the fibers of the thoracic diaphragm shorten and pull downward. This downward motion produces a piston-like pressure on the contents of the abdominopelvic cavity.

7-16. DIAPHRAGMATIC INHALATION 

As the thoracic diaphragm contracts and lowers, the vertical diameter of the thoracic cavity is increased. This increases the volume of the thoracic cavity. Thus, according to Boyle's law, the pressure of the air in the lungs decreases. The relatively higher atmospheric pressure outside pushes the air into the lungs, and the alveoli are inflated. 
At the same time, the thoracic diaphragm produces a pistol-like pressure upon the noncompressible fluid continuum in the abdominopelvic cavity. By Pascal's law, the resulting pressure is distributed equally to the elastic walls of the cavity. As these walls are stretched by the added pressure, they "store" potential energy. 
7-17. DIAPHRAGMATIC EXHALATION 

When the thoracic diaphragm relaxes, it no longer pushes down upon the contents of the abdominopelvic cavity. The potential energy stored in the stretched muscular walls becomes kinetic energy, and the walls rebound. This energy is sufficient for exhalation during quiet breathing. 
However, during forced breathing, the muscles of the abdominal wall will contract in accordance with the amount of air to be pushed out. 
As the muscles in the abdominal wall rebound (and contract in forced breathing), pressure is applied to the fluid continuum in the abdominopelvic cavity. By Pascal's law, this pressure is transferred to the underside of the thoracic diaphragm. The relaxed thoracic diaphragm is thus pushed up into the thoracic cavity. This decreases the vertical diameter and the volume of the thoracic cavity. The decreased volume results in increased pressure within the lungs (Boyle's law). Since the air pressure in the lungs is relatively greater than the outside atmospheric pressure, air is forced out through the respiratory passageways. (This is aided by the elastic rebound of tissues in the thoracic cavity.) 
 
 Lesson 5
DIGESTION AND ABSORPTION

6-15. INTRODUCTION

The small intestines are the primary area of the body for digestion of foodstuffs. Digestion occurs through the action of enzymes. The results of the digestion are the end-products. These end-products (molecules or particles) are of such size that they can be absorbed through the walls of the small intestines. The end-products are then distributed throughout the body by the body's circulatory systems.

6-16. DIGESTION AS A CHEMICAL PROCESS

a.      Digestion is the chemical process that breaks foodstuffs down into their basic constituents. In general, chemical processes are expected to occur at a rate proportional to the temperature. However, in the human body, the temperature is not high enough for the chemical process of digestion to produce a sufficient quantity of the materials needed.

b.      Therefore, digestive enzymes are present to maintain the appropriate rates of reaction. Digestive enzymes are catalysts. A catalyst is a substance that improves the rate of a reaction without being consumed itself. Because of digestive enzymes, digestion proceeds at a pace fast enough to provide the materials needed by the body.

c. The majority of digestion in humans takes place in the small intestines. The small intestines are located in the central part of the abdomen, immediately beneath the abdominal wall. In healthy individuals, a flap called the greater omentum is draped over the small intestines (between them and the anterior abdominal wall). The greater omentum has a great deal of fat for insulation. It is richly supplied with blood vessels for heat. Some might compare the greater omentum to an "electric blanket" for the small intestines.

FOODSTUFF ENZYME CLASS END PRODUCTS 
Carbohydrates Amylases Simple Sugars 
Lipids  Lipases Fatty Acids and Glycerol 
Proteins  Proteases Amino Acids 

Table 6-1. Foodstuffs, enzyme classes, and end-products of digestion. 

6-17. DIGESTIVE ENZYMES

a.      The digestive process begins in the oral cavity. The saliva contains enzymes which initiate the digestion of complex carbohydrates.

b.      In the stomach, the gastric glands produce enzymes that initiate the digestion of proteins.

c.      In the small intestines, there are digestive enzymes for all three classes of foodstuffs--carbohydrates, lipids, and proteins. Enzymes for completing the digestion of these three classes are found in the fluids produced by the pancreas and glands in the mucosa of the small intestines. Moreover, there is a fluid called bile that is produced by the liver and stored in the gallbladder for release into the small intestines. Bile helps in the digestion of lipids.

d.      The presence or absence of certain enzymes is genetically determined. Therefore, some individuals may have difficulty digesting certain foods.

6-18. TIME AND LENGTH

The length of the small intestines appears to be just right. The time it takes for material to travel from beginning to end is just about right for the completion of digestion.

6-19. ABSORPTION

The end-products of digestion are absorbed primarily through the walls of the small intestines.

a. Surface Area. The amount of absorption is proportional to the surface area of the walls which contact the contents. Two anatomical specializations serve to increase this surface area:

(1)     There are permanent circular folds (plicae circulares) in the mucosal lining of the small intestines. 
(2)     The entire inner surface of the mucosa is covered with villi. Villi are minute, fingerlike processes that extend into the lumen (cavity) of the small intestines. 
b. Capillaries. The simple sugars and amino acids are absorbed into the blood capillaries. Most of the fatty acids and glycerol are absorbed into the lymphatic capillaries.

6-20. HEPATIC VENOUS PORTAL SYSTEM

All of the blood capillaries in the absorptive areas of the digestive tract join to form the hepatic portal venous system. A venous portal system is a system that begins in capillaries, which join to form veins, which in turn end in another group of capillaries. The hepatic portal vein carries the blood from the absorptive areas of the digestive system to the liver.

6-21. THE LIVER

In the liver, a number of actions are performed on the blood. Excess materials are removed and stored. For example, some glucose is stored as glycogen. Toxic materials are degraded, microorganisms are removed, and so forth. The "treated" blood is then routed from the liver to the heart and then throughout the body.

6-22. UTILIZATION OF THE LIPIDS

The lipid materials, such as fatty acids and glycerol, are carried to the venous system beyond the liver. 

a.      Lipid materials are a high-energy item. They are stored as fat throughout the body so that they will be available when needed for energy. 
b.      Body fat also serves as insulation in the subcutaneous tissues. It gives buoyancy to the body in water. 
c.      Cholesterol is a very important substance in the body. It participates in the functioning of the liver and in other activities of the body. 
d.      However, there are certain medical conditions in which physicians prescribe a low-cholesterol and/or low-fat diet.  
 Lesson 5
MOTIVE FORCES INVOLVED IN DRIVING THE BLOOD THROUGH THE SYSTEM

10-32. INTRODUCTION

The blood (vehicle for transporting material) is driven through the blood vessels (conduits) by a variety of motive forces.

10-33. ARTERIAL BLOOD FLOW

Blood is driven through the arteries by a combination of forces. First, there is the force produced by the contraction of the ventricular walls. Second, there is the elastic recoil of the arterial walls. 

Systole. When the left ventricle contracts (systole), it forces the blood into the aortic arch. Above the base cylinder, the wall of the aortic arch is mainly elastic FCT. As the blood fills the aortic arch, the walls are stretched. 
Diastole. When the ventricle relaxes (diastole), the wall of the arch recoils and presses against the blood. With the closing of the aortic semilunar valve, the blood is forced to move out along the arteries in a pressure pulse. Since the elasticity of the arterial walls produces a continuous pressure, the blood moves continuously throughout the system. 
Arterial Pressures. The highest pressure is called the systolic pressure, and the lowest pressure is the diastolic pressure. 
Vasoconstriction. Vasoconstriction is the actual contraction of the arterial walls. Vasoconstriction can further increase the pressure on the blood in the arteries. 
Gravity. Gravity helps to move blood to the trunk and lower members. However, it is a hindrance in moving blood to the head and neck. 
10-34. VENOUS BLOOD FLOW

There is usually a low level of pressure in the veins. There are valves in the veins that ensure that blood flows continuously toward the heart. Therefore, as pressure is applied to a vein, there will be a pump effect. 

Pressure from Arteries. The muscular compartments of the upper and lower limbs tend to be full in healthy persons. Therefore, as blood enters the arteries within these compartments, a volume of blood must leave through the veins. 
Pressure from Muscular Contractions. During muscular activity, additional forces press against the veins and produce a "milking action." Again, blood moves through the veins back toward the heart. 
Gravity. In the head and neck, gravity helps to move the blood down through the veins. In the trunk and lower limbs, the valves help to prevent a backward flow of blood in the veins. 
 
 [[Anatomy and Physiology 101]]
Dendrites and axons are cytoplasmic extensions, or processes, that project from the cell body. They are sometimes referred to as fibers. Dendrites are usually, but not always, short and branching, which increases their surface area to receive signals from other neurons. The number of dendrites on a neuron varies. They are called afferent processes because they transmit impulses to the neuron cell body. There is only one axon that projects from each cell body. It is usually elongated and because it carries impulses away from the cell body, it is called an efferent process.
Developmental Aspects of the Nervous System

Maternal and environmental factors may impair embryonic brain development. Oxygen deprivation destroys brain cells. Severe congenital brain diseases include cerebral palsy, anencephaly, hydrocephalus, and spina bifida. 

Premature babies have trouble regulating body temperature because the hypothalamus is one of the last brain areas to mature prenatally. 

Development of motor control indicates the progressive myelination and maturation of a child's nervous system. Brain growth ends in young adulthood. Neurons die throughout life and are not replaced; thus, brain mass declines with age. 

Healthy aged people maintain nearly optimal intellectual function. Diseaseóparticularly cardiovascular diseases the major cause of declining mental function with age. 
Lesson 1
INTRODUCTION

6-1. GENERAL FUNCTION

The overall function of the human digestive system (Figure 6-1) is to provide materials to be used by the individual cells of the body. These materials are used by the cells: 

a.      As energy for life processes. 
b.      For growth and repair of body tissues. 


Figure 6-1. The human digestive system.
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0601.jpg]]


6-2. THE ENERGY CYCLE

The body requires that all of its energy be brought into it from external sources. 

a.      Solar Radiation. The ultimate source of all energy for living things on Earth is the Sun. This energy reaches the Earth in the form of solar radiation. 
b.      Photosynthesis. This radiant energy is stored by plants as the chemical bonds of glucose molecules. The process for doing this is called photosynthesis.
PHOTO = light
SYNTHESIS = put together 
This takes place in the presence of the green substance called chlorophyll.

6CO2 + 6H2O + E ® C6H12O6 + 6O2
Carbon Dioxide + Water + Energy YIELDS Glucose + Oxygen

c.      Food Consumption. The green plants are then utilized as food by various animals. Ultimately, either the green plants or the animals that ate the green plants are consumed by humans.

d.      Digestion and Metabolic Oxidation. Through the processes of digestion, the glucose is released. It is then delivered to the cells of the body by the circulatory system. Within the cells of the body, the energy is released from the glucose by the chemical process known as metabolic oxidation:

C6H12O6 + 6O2 ® 6CO2 + 6H2O + E
Glucose + Oxygen YIELDS Carbon Dioxide + Water + Energy

e.      Production and Use of ATP. The released energy is then used to produce the compound known as ATP (adenosine triphosphate). This metabolic oxidation and the production of ATP occur in the mitochondria. For this reason, the mitochondria are known as the "powerhouses" of the cell. When energy is required for carrying on any of the life processes, it is obtained from the ATP.

ATP  ®   ADP + P04 + E

ATP ¬   ADP + Phosphate Radical + Energy
http://training.seer.cancer.gov/module_anatomy/unit7_5_quiz_dd_01.html
Lesson 5
ELECTROCHEMICAL TRANSMISSION OF NEURON IMPULSES

2-14. INTRODUCTION 

The functional elements of the human nervous system are the neurons. The neurons are alined in sequences, one neuron after the other, to form circuits. The transmission of information along the length of a neuron is electrochemical in nature. 
An important fact is that "connecting" neurons do not actually touch each other. Instead, there is a space between the end of one and the beginning of the next ("continuity without contact"). A specified chemical, called a neurotransmitter, is required to cross the gap between one neuron and the next. 
12-15. RESTING POTENTIAL

As a part of their life processes, neurons are able to produce a concentration of negative ions inside and a concentration of positive ions outside of the cell membrane. The difference in the concentration of ions produces an electrical potential across the membrane. This condition is often referred to as polarization. When the neuron is not actually transmitting, this electrical potential across the membrane is known as the resting potential.

12-16. ACTION POTENTIAL (DEPOLARIZATION AND REPOLARIZATION)

Where a stimulus is applied to the neuron, the polarity of the ions is disrupted at the same location. Thus, that location is said to be depolarized. The ions in adjacent areas along the neuron then attempt to restore the original polarity at the location of the stimulus. However, as repolarization occurs in the area of the stimulus, the adjacent areas themselves become depolarized. This results in a wavelike progression of depolarization/repolarization along the length of the neuron. By this means, information is transferred along the neuron.

12-17. EFFECT OF THE THICKNESS OF THE NEURON PROCESSES

The speed with which an impulse travels is proportional to the thickness of the neuron process. The thickest processes (A fibers) have the fastest transmission (about 120 meters/second). The thinnest processes (C fibers) are the slowest (as slow as 1/2 meter/second). The B fibers (thicker than C fibers and thinner than A fibers) are faster than C fibers and slower than A fibers.

12-18. THE SYNAPSE

The gap between successive neurons is wide enough that impulses do not travel from one neuron to the next in the same way as along a single neuron. Information travels from one neuron to the next by means of a chemical neurotransmitter. Together, the gap and the "connecting" membranes of the neurons are called the synapse (Figure 12-8). The gap is called the synaptic cleft.



Figure 12-8. A synapse. 

Many synaptic vesicles (bundles of neurotransmitters) are found in the terminal bulb (bouton) of the first neuron. Each vesicle contains a quantum, a specific amount, of neurotransmitter or a substance used to make the neurotransmitter. 
When the impulse reaches the bouton, these vesicles are stimulated to release their neurotransmitter. The neurotransmitter then passes out of the bouton, through the presynaptic membrane, into the synaptic cleft. On the other side of the synaptic cleft is the postsynaptic membrane. This is the receptor site of the second neuron. 
The neurotransmitter is located only in the terminal bulb of the first neuron. For this reason, impulses travel in only one direction through the synapse, from the first to the second neuron. Since this process consumes much energy, there are many well-developed mitochondria in the bouton, or terminal bulb. 
12-19. THE NEUROMUSCULAR JUNCTION

While the synapse is the "connection" between two neurons, the neuromuscular junction (Figure 12-9) is the "connection" between a motor neuron and a striated muscle fiber.



Figure 12-9. A neuromuscular junction. 

In general terms, the neuromuscular junction and the synapse are physiologically identical. Synaptic vesicles in the enlarged bouton of the motor neuron contain the neurotransmitter acetylcholine (ACH). As an impulse reaches the bouton, ACH is released and passes through thepresynaptic membrane into the synaptic cleft. However, the surface of the postsynaptic membrane is in a series of longitudinal folds. This greatly increases the surface area receptive to the ACH. 
The motor unit is the group of striated muscle fibers innervated by the terminal arborization (tree-like branching) of one motor neuron. The fewer the muscle fibers found per motor unit, the more the muscle is capable of finer movements. As the number in the motor unit increases, the muscle action is coarser. When a muscle is to be used, the nervous system recruits just enough motor units to supply the strength needed for the work to be done. 

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1208.jpg]]
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1209.jpg]]
 Lesson 8
ELIMINATION OF UNUSED MATERIALS

6-34. UNDIGESTED FOOD MATERIALS 

Nondigestible Food Materials. A number of substances within food materials cannot be digested by the human digestive system. One important material in this group is called cellulose. Cellulose is a complex carbohydrate found in plants. Cellulose is commonly referred to as "bulk" or "fiber." 
Other Undigested Food Materials. When individuals consume great quantities of foods, a portion of it will not be digested. 
Passage Out of the Small Intestines. This undigested material will pass out of the small intestines with the non-digestible materials. The resulting fluid mass enters the large intestines through the ileocecal valve. 
6-35. LARGE INTESTINES 

Consolidation of Contents. In the large intestines, this fluid mass is gradually consolidated into a semisolid mass called feces. The major function of the large intestines then is salvage. Water is the primary salvage item. In addition to water, some previously unabsorbed endproducts of digestion can be absorbed here. At the same time certain excretions from the body can be deposited in the fecal mass. 
Mucus. As the contents increase in solidity, mucus is added to facilitate their movement through the large intestines. (Previously, we have seen the addition of mucus to the bolus in the mouth to facilitate movement.) This mucus is produced by unicellular glands in the mucosal lining of the large intestines. (Because of their microscopic appearance, these unicellular glands are called goblet cells.) 
Organisms. Many microorganisms are found within the lumen or cavity of the large intestines. Certain microorganisms are responsible for the production of vitamin K. Depending on the type of food present, some species of microorganisms produce various gases (flatulence). On occasion, pathogenic organisms may be present and cause problems for the individual. 
6-36. STORAGE OF FECES

Toward the lower end of the large intestines, the contents (feces) have become relatively consolidated. This consolidated mass is retained (stored) mainly in the rectum and the lower portion of the sigmoid colon.

6-37. ELIMINATION

At the appropriate time, the feces is passed out of the body (defecation). The feces passes through the anal canal and anus. This is accomplished by the relaxation of the anal sphincter muscles.
 
 Lesson 11
EXCHANGE AND TRANSPORTATION OF GASES: ARTIFICIAL BREATHING/RESUSCITATION

7-40. EXCHANGE AND TRANSPORTATION OF GASES 

Gases Involved. Oxygen and carbon dioxide are the primary gases involved in respiration. Under special circumstances, nitrogen may also be of concern. 
Pressure Gradients. A gas moves from an area where its pressure is greater to an area where its pressure is less. Thus, the movement of gases depends upon such pressure gradients. 
External Respiration. At the alveoli, gases are exchanged between the air inside and the blood in the adjacent capillaries. 
Internal Respiration. Within the body, gases are exchanged between the blood of the capillaries and the individual cells of the body. 
Transportation of Gases. The gases are transported (Figure 7-5) between the alveoli and the individual cells by the cardiovascular system. 
(1)  Some of the gases are dissolved directly in the plasma of the blood. 
(2  However, in humans, the greater percentage of the gases is carried within the substance of the RBCs (red blood cells, erythrocytes). The RBC, found in great numbers in the blood, is specially constructed for transporting the gases. Hemoglobin, a substance found within RBCs, has a great affinity for oxygen. Yet, the hemoglobin can readily give up the oxygen wherever it is needed. 

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0705.jpg]]
Figure 7-5. Scheme of the exchange of the gases.

7-41. ARTIFICIAL BREATHING/RESUSCITATION

When an individual stops breathing, he will soon die if the tissues of the body, particularly the brain, do not get a fresh supply of oxygen. 

Various mechanical devices are sometimes used to maintain breathing. One is the pulmotor. 
In "mouth-to-mouth" resuscitation, the operator forces air from his own respiratory system into the respiratory system of the patient. Fortunately, the initial air forced into the patient is the "dead air" of the operator and still has its full amount of oxygen. 
There are also various techniques for manipulating the patient's rib cage to simulate normal function. 
At times, gravity may be used to assist a patient. In particular postures, a patient may find breathing easier. Also, under certain circumstances, a patient may be positioned to drain accumulated fluids from specific parts of the lungs. 
 
http://en.wikipedia.org/wiki/Electron_Transport_Chain

Electron transport chain
From Wikipedia, the free encyclopedia
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The Electron Transport Chain. Not all structures represent current knowledge of electron transport chains -- see talk page for more details. 
Photosynthetic electron transport chain of the thylakoid membrane.An electron transport chain associates electron carriers (such as NAD+ and FADH2) and mediating biochemical reactions that produce adenosine triphosphate (ATP), which is the energy currency of life. Only two sources of energy are available to living organisms: oxidation-reduction (redox) reactions and sunlight (used for photosynthesis). Organisms that use redox reactions to produce ATP are called chemotrophs. Organisms that use sunlight are called phototrophs. Both chemotrophs and phototrophs utilize electron transport chains to convert energy into ATP. This is achieved through a three step process:

Gradually sap energy from high-energy electrons in a series of individual steps, 
Use that energy to forcibly unbalance the proton concentration across the membrane, creating an electrochemical gradient, 
Use the energy released by the drive to rebalance the proton distribution as a means of producing ATP. 
Contents [hide]
1 Background 
2 Electron transport chains in mitochondria 
2.1 Mitochondrial redox carriers 
2.1.1 Complex I 
2.1.2 Complex II 
2.1.3 Complex III 
2.1.4 Complex IV 
2.2 Coupling with oxidative phosphorylation 
2.3 Summary 
3 Electron transport chains in bacteria 
3.1 Electron donors 
3.2 Dehydrogenases 
3.3 Quinone carriers 
3.4 Proton pumps 
3.5 Cytochrome electron carriers 
3.6 Terminal oxidases and reductases 
3.7 Electron acceptors 
3.8 Summary 
4 Photosynthetic electron transport chains 
5 Evolution 
6 Electron transport chain in aging 
7 Summary 
8 References 
9 External links 
 


[edit] Background
ATP is made by an enzyme called ATP synthase. The structure of this enzyme and its underlying genetic code is remarkably conserved in all known forms of life.

ATP synthase is powered by a transmembrane electrochemical potential gradient, usually in the form of a proton gradient. The function of the electron transport chain is to produce this gradient. In all living organisms, a series of redox reactions are used to produce a transmembrane electrochemical potential gradient.

Redox reactions are chemical reactions in which electrons are transferred from a donor molecule to an acceptor molecule. The underlying force driving these reactions is the Gibbs free energy of the reactants and products. The Gibbs free energy is the energy available (“free”) to do work. Any reaction that decreases the overall Gibbs free energy of a system will proceed spontaneously.

The transfer of electrons from a high-energy molecule (the donor) to a lower-energy molecule (the acceptor) can be spatially separated into a series of intermediate redox reactions. This is an electron transport chain.

The fact that a reaction is thermodynamically possible does not mean that it will actually occur; for example, a mixture of hydrogen gas and oxygen gas does not spontaneously ignite. It is necessary either to supply an activation energy, or to lower the intrinsic activation energy of the system, in order to make most biochemical reactions proceed at a useful rate. Living systems use complex macromolecular structures (enzymes) to lower the activation energies of biochemical reactions.

It is possible to couple a thermodynamically favorable reaction (a transition from a high-energy state to a lower-energy state) to a thermodynamically unfavorable reaction (such as a separation of charges, or the creation of an osmotic gradient), in such a way that the overall free energy of the system decreases (making it thermodynamically possible), while useful work is done at the same time. Biological macromolecules that catalyze a thermodynamically unfavorable reaction if and only if a thermodynamically favorable reaction occurs simultaneously underlie all known forms of life.

Electron transport chains capture energy in the form of a transmembrane electrochemical potential gradient. This energy can then be harnessed to do useful work. The gradient can be used to transport molecules across membranes. It can be used to do mechanical work, such as rotating bacterial flagella. It can be used to produce ATP high-energy molecules that are necessary for growth.

A small amount of ATP is available from substrate-level phosphorylation (for example, in glycolysis). Some organisms can obtain ATP exclusively by fermentation. In most organisms, however, the majority of ATP is generated by electron transport chains.


[edit] Electron transport chains in mitochondria
The cells of all eukaryotes (all animals, plants, fungi, algae, protozoa – in other words, all living things except bacteria and archaea) contain intracellular organelles called mitochondria that produce ATP. Energy sources such as glucose are initially metabolized in the cytoplasm. The products are imported into mitochondria. Mitochondria continue the process of catabolism using metabolic pathways including the Krebs cycle, fatty acid oxidation and amino acid oxidation.

The end result of these pathways is the production of two energy-rich electron donors, NADH and FADH2. Electrons from these donors are passed through an electron transport chain to oxygen, which is reduced to water. This is a multi-step redox process that occurs on the mitochondrial inner membrane. The enzymes that catalyze these reactions have the remarkable ability to simultaneously create a proton gradient across the membrane, producing a thermodynamically unlikely high-energy state with the potential to do work. Although electron transport occurs with great efficiency, a small percentage of electrons are prematurely leaked to oxygen, resulting in the formation of the toxic free radical, superoxide.

The similarity between intracellular mitochondria and free-living bacteria is striking. The known structural, functional and DNA similarities between mitochondria and bacteria provide strong evidence that mitochondria evolved from intracellular prokaryotic symbionts that took up residence in primitive eukaryotic cells.


[edit] Mitochondrial redox carriers
 
Stylized representation of the ETC. Energy obtained through the transfer of electrons (black arrows) down the ETC is used to pump protons (red arrows) from the mitochondrial matrix into the intermembrane space, creating an electrochemical proton gradient across the mitochondrial inner membrane (IMM) called ΔΨ. This electrochemical proton gradient allows ATPhigh synthase to use the flow of H+ through the enzyme back into the matrix to generate ATP from adenosine diphosphate (ADP) and inorganic phosphate. Complex I (NADH coenxyme Q reductase; labeled I) accepts electrons from the Krebs cycle electron carrier nicotinamide adenine dinucleotide (NADH), and passes them to coenzyme Q (ubiquinone; labeled UQ), which also receives electrons from complex II (succinate dehydrogenase; labeled II). UQ passes electrons to complex III (cytochrome bc1 complex; labeled III), which passes them to cytochrome c (cyt c). Cyt c passes electrons to Complex IV (cytochrome c oxidase; labeled IV), which uses the electrons and hydrogen ions to reduce molecular oxygen to water.
Four membrane-bound complexes have been identified in mitochondria. Each is an extremely complex transmembrane structure that is embedded in the inner membrane. Three of them are proton pumps. The structures are electrically connected by lipid-soluble electron carriers and water-soluble electron carriers. The overall electron transport chain

              NADH → Complex I → Q → Complex III → cytochrome c → Complex IV  → O2
                                 ↑                                                                                      
                             Complex II                                                                                     

                                                 

[edit] Complex I
Complex I (NADH dehydrogenase, also called NADH:ubiquinone oxidoreductase; EC 1.6.5.3) removes two electrons from NADH and transfers them to a lipid-soluble carrier, ubiquinone (Q). The reduced product, ubiquinol (QH2) is free to diffuse within the membrane. At the same time, Complex I moves four protons (H+) across the membrane, producing a proton gradient. Complex I is one of the main sites at which premature electron leakage to oxygen occurs, thus being one of main sites of production of a harmful free radical called superoxide.

The pathway of electrons occurs as follows:

NADH is oxidized to NAD+, reducing Flavin mononucleotide to FMNH2 in one two-electron step. The next electron carrier is a Fe-S cluster, which can only accept one electron at a time to reduce the ferric ion into a ferrous ion. Conveniently, FMNH2 can only be oxidized in two one-electron steps, through a semiquinone intermediate. The electron thus travels from the FMNH2 to the Fe-S cluster, then from the Fe-S cluster to the oxidized Q to give the free-radical (semiquinone) form of Q. This happens again to reduce the semiquinone form to the ubiquinol form, QH2. During this process, four protons are translocated across the inner mitochondrial membrane, from the matrix to the intermembrane space. This creates a proton gradient that will be later used to generate ATP through oxidative phosphorylation.


[edit] Complex II
Complex II (succinate dehydrogenase; EC 1.3.5.1) is not a proton pump. It serves to funnel additional electrons into the quinone pool (Q) by removing electrons from succinate and transferring them (via FAD) to Q. Complex II consists of four protein subunits: SDHA,SDHB,SDHC, and SDHD. Other electron donors (e.g. fatty acids and glycerol 3-phosphate) also funnel electrons into Q (via FAD), again without producing a proton gradient.


[edit] Complex III
Complex III (cytochrome bc1 complex; EC 1.10.2.2) removes in a stepwise fashion two electrons from QH2 and transfers them to two molecules of cytochrome c, a water-soluble electron carrier located within the intermembrane space. At the same time, it moves two protons across the membrane, producing a proton gradient (in total 4 protons: 2 protons are translocated and 2 protons are released from ubiquinol). When electron transfer is hindered (by a high membrane potential, point mutations or respiratory inhibitors such as antimycin A), Complex III may leak electrons to oxygen resulting in the formation of superoxide, a highly toxic species, which is thought to contribute to the pathology of a number of diseases, including aging.


[edit] Complex IV
Complex IV (cytochrome c oxidase; EC 1.9.3.1) removes four electrons from four molecules of cytochrome c and transfers them to molecular oxygen (O2), producing two molecules of water (H2O). At the same time, it moves four protons across the membrane, producing a proton gradient.


[edit] Coupling with oxidative phosphorylation
The chemiosmotic coupling hypothesis, as proposed by Nobel Prize in Chemistry winner Peter D. Mitchell, explains that the electron transport chain and oxidative phosphorylation are coupled by a proton gradient across the inner mitochondrial membrane. The efflux of protons creates both a pH gradient and an electrochemical gradient. This proton gradient is used by the FOF1 ATP synthase complex to make ATP via oxidative phosphorylation. ATP synthase is sometimes regarded as complex V of the electron transport chain. The FO component of ATP synthase acts as an ion channel for return of protons back to mitochondrial matrix. During their return, the free energy produced during the generation of the oxidized forms of the electron carriers (NAD+ and FAD) is released. This energy is used to drive ATP synthesis, catalyzed by the F1 component of the complex.
Coupling with oxidative phosphorylation is a key step for ATP production. However, in certain cases uncoupling may be biologically useful. The inner mitochondrial membrane of brown adipose tissue contains a large amount of thermogenin (an uncoupling protein) which acts as uncoupler by forming an alternative pathway for the flow of protons back to matrix. This results in consumption of energy in thermogenesis rather than ATP production. This may be useful in cases when heat production is required, for example in colds or during arise of hibernating animals. Synthetic uncouplers, e.g. 2,4-dinitrophenol also exist and at high doses, are lethal.


[edit] Summary
The mitochondrial electron transport chain removes electrons from an electron donor (NADH or FADH2) and passes them to a terminal electron acceptor (O2) via a series of redox reactions. These reactions are coupled to the creation of a proton gradient across the mitochondrial inner membrane. There are three proton pumps: I, III and IV. The resulting transmembrane proton gradient is used to make ATP via ATP synthase.

The reactions catalyzed by Complex I and Complex III exist roughly at equilibrium. The steady-state concentrations of the reactants and products are approximately equal. This means that these reactions are readily reversible, simply by increasing the concentration of the products relative to the concentration of the reactants (for example, by increasing the proton gradient). ATP synthase is also readily reversible. Thus ATP can be used to make a proton gradient, which in turn can be used to make NADH. This process of reverse electron transport is important in many prokaryotic electron transport chains.


[edit] Electron transport chains in bacteria
In eukaryotes, NADH is the most important electron donor. The associated electron transport chain is

NADH → Complex I → Q → Complex III → cytochrome c → Complex IV → O2 where Complexes I, III and IV are proton pumps, while Q and cytochrome c are mobile electron carriers. The electron acceptor is molecular oxygen.

In prokaryotes (bacteria and archaea) the situation is more complicated, because there are a number of different electron donors and a number of different electron acceptors. The generalized electron transport chain in bacteria is:

                     Donor            Donor                    Donor                                                  
                       ↓                ↓                        ↓                                            
                 dehydrogenase   →   quinone   →   bc1   →   cytochrome 
                                        ↓                        ↓
                                oxidase(reductase)       oxidase(reductase)                   
                                        ↓                        ↓                                         
                                     Acceptor                 Acceptor                       
  
Note that electrons can enter the chain at three levels: at the level of a dehydrogenase, at the level of the quinone pool, or at the level of a mobile cytochrome electron carrier. These levels correspond to successively more positive redox potentials, or to successively decreased potential differences relative to the terminal electron acceptor. In other words, they correspond to successively smaller Gibbs free energy changes for the overall redox reaction Donor → Acceptor.

Individual bacteria use multiple electron transport chains, often simultaneously. Bacteria can use a number of different electron donors, a number of different dehydrogenases, a number of different oxidases and reductases, and a number of different electron acceptors. For example, E. coli (when growing aerobically using glucose as an energy source) uses two different NADH dehydrogenases and two different quinol oxidases, for a total of four different electron transport chains operating simultaneously.

A common feature of all electron transport chains is the presence of a proton pump to create a transmembrane proton gradient. Bacterial electron transport chains may contain as many as three proton pumps, like mitochondria, or they may contain only one or two. They always contain at least one proton pump.


[edit] Electron donors
In the present day biosphere, the most common electron donors are organic molecules. Organisms that use organic molecules as an energy source are called organotrophs. Organotrophs (animals, fungi, protists) and phototrophs (plants and algae) constitute the vast majority of all familiar life forms.

Some prokaryotes can use inorganic matter as an energy source. Such organisms are called lithotrophs (“rock-eaters”). Inorganic electron donors include hydrogen, carbon monoxide, ammonia, nitrite, sulfur, sulfide, and ferrous iron. Lithotrophs have been found growing in rock formations thousands of meters below the surface of the Earth. Because of their volume of distribution, lithotrophs may actually outnumber organotrophs and phototrophs in our biosphere.

The use of inorganic electron donors as an energy source is of particular interest in the study of evolution. This type of metabolism must logically have preceded the use of organic molecules as an energy source.


[edit] Dehydrogenases
Bacteria can use a number of different electron donors. When organic matter is the energy source, the donor may be NADH or succinate, in which case electrons enter the electron transport chain via NADH dehydrogenase (similar to Complex I in mitochondria) or succinate dehydrogenase (similar to Complex II). Other dehydrogenases may be used to process different energy sources: formate dehydrogenase, lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, H2 dehydrogenase (hydrogenase) etc. Some dehydrogenases are also proton pumps; others simply funnel electrons into the quinone pool.

Most dehydrogenases are synthesized only when needed. Depending on the environment in which they find themselves, bacteria select different enzymes from their DNA library and synthesize only those that are needed for growth. Enzymes that are synthesized only when needed are said to be inducible.


[edit] Quinone carriers
Quinones are mobile, lipid-soluble carriers that shuttles electrons (and protons) between large, relatively immobile macromolecular complexes imbedded in the membrane. Bacteria use ubiquinone (the same quinone that mitochondria use) and related quinones such as menaquinone.


[edit] Proton pumps
A proton pump is any process that creates a proton gradient across a membrane. Protons can be physically moved across a membrane; this is seen in mitochondrial Complexes I and IV. The same effect can be produced by moving electrons in the opposite direction. The result is the disappearance of a proton from the cytoplasm and the appearance of a proton in the periplasm. Mitochondrial Complex III uses this second type of proton pump, which is mediated by a quinone (the Q cycle).

Some dehydrogenases are proton pumps; others are not. Most oxidases and reductases are proton pumps, but some are not. Cytochrome bc1 is a proton pump found in many, but not all, bacteria (it is not found in E. coli). As the name implies, bacterial bc1 is similar to mitochondrial bc1 (Complex III).

Proton pumps are the heart of the electron transport process. They produce the transmembrane electrochemical gradient that supplies energy to the cell.


[edit] Cytochrome electron carriers
Cytochromes are pigments that contain iron. They are found in two very different environments.

Some cytochromes are water-soluble carriers that shuttle electrons to and from large, immobile macromolecular structures imbedded in the membrane. The mobile cytochrome electron carrier in mitochondria is cytochrome c. Bacteria use a number of different mobile cytochrome electron carriers.

Other cytochromes are found within macromolecules such as Complex III and Complex IV. They also function as electron carriers, but in a very different, intramolecular, solid-state environment.

Electrons may enter an electron transport chain at the level of a mobile cytochrome or quinone carrier. For example, electrons from inorganic electron donors (nitrite, ferrous iron etc.) enter the electron transport chain at the cytochrome level. When electrons enter at a redox level greater than NADH, the electron transport chain must operate in reverse to produce this necessary, higher-energy molecule.


[edit] Terminal oxidases and reductases
When bacteria grow in aerobic environments, the terminal electron acceptor (O2) is reduced to water by an enzyme called an oxidase. When bacteria grow in anaerobic environments, the terminal electron acceptor is reduced by an enzyme called a reductase.

In mitochondria the terminal membrane complex (Complex IV) is cytochrome oxidase. Aerobic bacteria use a number of different terminal oxidases. For example, E. coli does not have a cytochrome oxidase or a bc1 complex. Under aerobic conditions it uses two different terminal quinol oxidases (both proton pumps) to reduce oxygen to water.

Anaerobic bacteria, which do not use oxygen as a terminal electron acceptor, have terminal reductases individualized to their terminal acceptor. For example, E. coli can use fumarate reductase, nitrate reductase, nitrite reductase, DMSO reductase, or trimethylamine-N-oxide reductase, depending on the availability of these acceptors in the environment.

Most terminal oxidases and reductases are inducible. They are synthesized by the organism as needed, in response to specific environmental conditions.


[edit] Electron acceptors
Just as there are a number of different electron donors (organic matter in organotrophs, inorganic matter in lithotrophs), there are a number of different electron acceptors, both organic and inorganic. If oxygen is available, it is invariably used as the terminal electron acceptor, because it generates the greatest Gibbs free energy change and produces the most energy.

In anaerobic environments, different electron acceptors are used, including nitrate, nitrite, ferric iron, sulfate, carbon dioxide, and small organic molecules such as fumarate.

Since electron transport chains are redox processes, they can be described as the sum of two redox pairs. For example, the mitochondrial electron transport chain can be described as the sum of the NAD+/NADH redox pair and the O2/H2O redox pair. NADH is the electron donor and O2 is the electron acceptor.

Not every donor-acceptor combination is thermodynamically possible. The redox potential of the acceptor must be more positive than the redox potential of the donor. Furthermore, actual environmental conditions may be far different from standard conditions (1 molar concentrations, 1 atm partial pressures, pH = 7) which apply to standard redox potentials. For example, hydrogen-evolving bacteria grow at an ambient partial pressure of hydrogen gas of 10-4 atm. The associated redox reaction, which is thermodynamically favorable in nature, is thermodynamically impossible under “standard” conditions.


[edit] Summary
Bacterial electron transport pathways are, in general, inducible. Depending on their environment, bacteria can synthesize different transmembrane complexes and produce different electron transport chains in their cell membranes. Bacteria select their electron transport chains from a DNA library containing multiple possible dehydrogenases, terminal oxidases and terminal reductases. The situation is often summarized by saying that electron transport chains in bacteria are branched, modular and inducible.


[edit] Photosynthetic electron transport chains
In oxidative phosphorylation, electrons are transferred from a high-energy electron donor (e.g. NADH) to an electron acceptor (e.g. O2) through an electron transport chain. In photophosphorylation, the energy of sunlight is used to create a high-energy electron donor and an electron acceptor. Electrons are then transferred from the donor to the acceptor through another electron transport chain.

Photosynthetic electron transport chains have many similarities to the oxidative chains discussed above. They use mobile, lipid-soluble carriers (quinones) and mobile, water-soluble carriers (cytochromes, etc.). They also contain a proton pump. Remarkably, the proton pump in all photosynthetic chains resembles mitochondrial Complex III.

Photosynthetic electron transport chains are discussed in greater detail in the articles Photophosphorylation, Photosynthesis, Photosynthetic reaction center and Light-dependent reaction.


[edit] Evolution
The similarities in structure, function and genetic code between electron transport chains found in present-day eukarya, bacteria and archaea imply a common evolutionary origin. It is possible to make an educated guess as to the type of electron transport processes that must have preceded the evolution of eukarya, bacteria and archaea as separate domains of life, although current evidence does not support or deny any such proposed ETC systems. [1] For example, the earliest organisms may have had a transmembrane potential gradient. There may have been an associated ATP-like molecule, an associated ATP synthase, and an associated proton pump. This is an area of active research.


[edit] Electron transport chain in aging
The transcriptional profile of 95 genes responsible for proteins involved in the electron transport chain has been identified as a cross species aging signature.[2]


[edit] Summary
Electron transport chains are the source of energy for all known forms of life. They are redox reactions that transfer electrons from an electron donor to an electron acceptor. The transfer of electrons is coupled to the translocation of protons across a membrane, producing a proton gradient. The proton gradient is used to produce useful work.

The coupling of thermodynamically favorable to thermodynamically unfavorable biochemical reactions by biological macromolecules is an example of an emergent property – a property that could not have been predicted, even given full knowledge of the primitive geochemical systems from which these macromolecules evolved. It is an open question whether such emergent properties evolve only by chance, or whether they necessarily evolve in any large biogeochemical system, given the underlying laws of physics.


[edit] References
^ Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walter, Molecular Biology of the Cell 4th edition; IV. Internal Organization of the Cell 14. Energy Conversion: Mitochondria and Chloroplasts online version hosted by NCBI 
^ Zahn J, Sonu R, Vogel H, Crane E, Mazan-Mamczarz K, Rabkin R, Davis R, Becker K, Owen A, Kim S (2006). "Transcriptional profiling of aging in human muscle reveals a common aging signature". PLoS Genet 2 (7): e115. PMID 16789832.  
Fenchel T; King GM, Blackburn TH (Sep 2006). Bacterial Biogeochemistry: The Ecophysiology of Mineral Cycling, 2nd ed., Elsevier. ISBN 978-0121034559.  
Lengeler JW; Drews G; Schlegel HG (editors) (Jan 1999). Biology of the Prokaryotes. Blackwell Science. ISBN 978-0632053575.  
Nelson DL; Cox MM (Apr 2005). Lehninger Principles of Biochemistry, 4th ed, W. H. Freeman. ISBN 978-0716743392.  
Nicholls DG; Ferguson SJ (Jul 2002). Bioenergetics 3. Academic Press. ISBN 978-0125181211.  
Stumm W (1996). Aquatic Chemistry, 3rd ed, Wiley. ISBN 978-0471511854.  
Thauer RK; Jungermann K; Decker K (Mar 1977). "Energy conservation in chemotrophic anaerobic bacteria". Bacteriol Rev 41 (1): 100-80. PMID 860983.  
White D. (Sep 1999). The Physiology and Biochemistry of Prokaryotes, 2nd ed., Oxford University Press. ISBN 978-0195125795.  
Voet D; Voet JG (Mar 2004). Biochemistry, 3rd ed, Wiley. ISBN 978-0471586517.  

[edit] External links
MeSH Electron+Transport+Chain+Complex+Proteins 
UMich Orientation of Proteins in Membranes families/superfamily-3 - Complexes with cytochrome b-like domains 
UMich Orientation of Proteins in Membranes families/superfamily-4 - Bacterial and mitochondrial cytochrome c oxidases 
UMich Orientation of Proteins in Membranes families/superfamily-2 - Photosynthetic reaction centers and photosystems 
UMich Orientation of Proteins in Membranes families/superfamily-78 - Cytochrome c family 
UMich Orientation of Proteins in Membranes families/superfamily-101 - Cupredoxins 
UMich Orientation of Proteins in Membranes protein/pdbid-1e6e - Adrenodoxin reductase 
UMich Orientation of Proteins in Membranes families/superfamily-130 - Electron transfer flavoproteins 
[show]v • d • eCellular Respiration 
Aerobic Respiration Glycolysis → Pyruvate Decarboxylation → Citric Acid Cycle → Oxidative Phosphorylation (Electron Transport Chain + ATP synthase) 
Anaerobic Respiration Glycolysis → Lactic Acid Formation or Ethanol Formation 
[show]v • d • eMitochondrial electron transport chain/oxidative phosphorylation 
Complex I - Complex II - Coenzyme Q - Complex III - Cytochrome C - Complex IV - Alternative oxidase - Electron-transferring-flavoprotein dehydrogenase 

Retrieved from "http://en.wikipedia.org/wiki/Electron_transport_chain"
Categories: Cellular respiration | Integral membrane proteins
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1101.jpg]]

-1. ENDOCRINE ORGANS

ENDO = within
CRINE = secrete

The endocrine system (Figure 11-1) is a loose collection of organs called endocrine glands.



Figure 11-1. The endocrine glands of the human body and their locations. 

The endocrine glands are organs of internal secretion. Since they lack a duct system, they are often referred to as ductless glands. 
Since their secretions pass into the blood, they are usually well supplied with blood vessels. 
11-2. HORMONE

The secretion of an endocrine organ is called a hormone. The hormone is a chemical required in very small amounts for the proper development and/or functioning of the body. (Note the similarity of this definition to that of a vitamin. However, the hormone is produced within the body, and the vitamin is acquired from without.)

11-3. TARGET ORGAN AND FEEDBACK MECHANISM

When the hormone is secreted by the endocrine organ, it is carried by the blood to the appropriate organ, the target organ. In addition, the level of activity of the target organ often affects the activity of the endocrine organ. Thus, there is a feedback mechanism that causes the endocrine organ to secrete just the right amount of hormone.
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The Endocrine System and Hormone Function Overview

The endocrine system (Figure 9.1)is a major controlling system of the body. Through hormones, it stimulates such long-term processes as growth and development, metabolism, reproduction, and body defense. 

Endocrine organs are small and widely separated in the body. Some are mixed glands (both endocrine and exocrine in function). Others are purely hormone producing. 

All hormones are fat-souble (steroid)or water-soluble (amino acid-based) hormones. 

Endocrine organs are activated to release their hormones into the blood by hormonal, humoral, or neural stimuli. Negative feedback is important in regulating hormone levels in the blood. 

Blood-borne hormones alter the metabolic activities of their target organs. The ability of a target organ to respond to a hormone depends on the presence of receptors in or on its cells to which the hormone binds or attaches. 

Fat-soluble (steroid) hormones directly influence the target cell's DNA by binding to receptor sites in the nucleus (Figure 9.2). Water-soluble (amino acid-based) hormones act through second messengers (Figure 9.3). 
Endocytosis is a process whereby cells absorb material (molecules such as proteins) from the outside by engulfing it with their cell membrane. It is used by all cells of the body because most substances important to them are large polar molecules, and thus cannot pass through the hydrophobic plasma membrane. The function of endocytosis is the opposite of [[exocytosis]].

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Epithelial membranes consist of epithelial tissue and the connective tissue to which it is attached. The two main types of epithelial membranes are the mucous membranes and serous membranes 
http://en.wikipedia.org/wiki/Epithelium

Epithelium
From Wikipedia, the free encyclopedia
• Ten things you didn't know about images on Wikipedia •Jump to: navigation, search
This article is about the epithelium as it relates to animal anatomy. For the fungal structure of the same name, see Pileipellis.
 
Types of epitheliumIn biology and medicine, epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. The outermost layer of our skin is composed of dead stratified squamous, keratinized epithelial cells.

Mucous membranes lining the inside of the mouth, the esophagus, and part of the rectum are lined by nonkeratinized stratified squamous epithelium. Other, open to outside body cavities are lined by simple squamous or columnar epithelial cells.

Other epithelial cells line the insides of the lungs, the gastrointestinal tract, the reproductive and urinary tracts, and make up the exocrine and endocrine glands. The outer surface of the cornea is covered with fast-growing, easily-regenerated epithelial cells.

Functions of epithelial cells include secretion, absorption, protection, transcellular transport, sensation detection, and selective permeability.

Endothelium (the inner lining of blood vessels, the heart, and lymphatic vessels) is a specialized form of epithelium. Another type, Mesothelium, forms the walls of the pericardium, pleurae, and peritoneum.

In humans, epithelium is classified as a primary body tissue, the other ones being connective tissue, muscle tissue and nervous tissue.

Contents [hide]
1 Classification 
1.1 Shape 
1.2 Stratification 
1.3 Specializations 
2 Examples 
3 Cell junctions 
4 Secretory epithelia 
5 Embryology 
6 Additional images 
7 Links 
8 References 
 


[edit] Classification
Epithelial cells are classified by the following three factors:

Shape 
Stratification 
Specializations 

[edit] Shape
Squamous: All Squamous cells are flat cells with an irregular flattened shape. A one-cell layer of simple squamous epithelium forms the alveoli of the respiratory membrane, and the endothelium of capillaries, and is a minimal barrier to diffusion. Other places where squamous cells can be found include the filtration tubules of the kidneys, and the major cavities of the body. These cells are relatively inactive metabolically, and are associated with the diffusion of water, electrolytes, and other substances. 
Cuboidal: As the name suggests, these cells have a shape similar to a cube, meaning its width is the same size as its height. The nuclei of these cells are usually located in the center. 
Columnar: These cells are taller than they are wide. Simple columnar epithelium is made up of a single layer of cells that are longer than they are wide. The nucleus is also closer to the base of the cell. The small intestine is a tubular organ lined with this type of tissue. Unicellular glands called goblet cells are scattered throughout the simple columnar epithelial cells and secrete mucus. The free surface of the columnar cell has tiny hairlike projections called microvilli. They increase the surface area for absorption. 
Transitional: This is a specialized type of epithelium found lining organs that can stretch, such as the urothelium that lines the bladder and ureter of mammals. Since the cells can slide over each other, the appearance of this epithelium depends on whether the organ is distended or contracted: if distended, it appears as if there are only a few layers; when contracted, it appears as if there are several layers. 

[edit] Stratification
Simple: There is a single layer of cells. 
Stratified: More than one layer of cells. The superficial layer is used to classify the layer. Only one layer touches the basal lamina. Stratified cells can usually withstand large amounts of stress. 
Pseudostratified with cilia: This is used mainly in one type of classification (pseudostratified columnar epithelium). There is only a single layer of cells, but the position of the nuclei gives the impression that it is stratified. If a specimen looks stratified, but you can identify cilia, the specimen is pseudostratified ciliated epithelium since stratified epithelium cannot have cilia but may be very rarely found in fetal oesophagus. A cell that contains hairs will be around ten times stronger than a regular cell 

[edit] Specializations
Keratinized cells contain keratin (a cytoskeletal protein). While keratinized epithelium occurs mainly in the skin, it is also found in the mouth and nose, providing a tough, impermeable barrier. 
Ciliated cells have apical plasma membrane extensions composed of microtubules capable of beating rhythmically to move mucus or other substances through a duct. Cilia are common in the respiratory system and the lining of the oviduct. 

[edit] Examples
System   Tissue   Epithelium   Subtype   
circulatory blood vessels Simple squamous endothelium 
digestive ducts of submandibular glands Stratified columnar - 
digestive attached gingiva Stratified squamous, keratinized - 
digestive dorsum of tongue Stratified squamous, keratinized - 
digestive hard palate Stratified squamous, keratinized - 
digestive esophagus Stratified squamous, non-keratinised - 
digestive stomach Simple columnar, non-ciliated - 
digestive small intestine Simple columnar, non-ciliated - 
digestive large intestine Simple columnar, non-ciliated - 
digestive rectum Stratified squamous, non-keratinised - 
digestive anus Stratified squamous, keratinised - 
digestive gallbladder Simple columnar, non-ciliated - 
endocrine thyroid follicles Simple cuboidal - 
nervous ependyma Simple cuboidal - 
lymphatic lymph vessel Simple squamous endothelium 
integumentary skin - dead superficial layer Stratified squamous, keratinized - 
integumentary sweat gland ducts Stratified cuboidal - 
integumentary mesothelium of body cavities Simple squamous - 
reproductive - female ovaries Simple cuboidal germinal epithelium (female) 
reproductive - female Fallopian tubes Simple columnar, ciliated - 
reproductive - female uterus Simple columnar, ciliated - 
reproductive - female endometrium Simple columnar - 
reproductive - female cervix (endocervix) Simple columnar - 
reproductive - female cervix (ectocervix) Stratified squamous, non-keratinised - 
reproductive - female vagina Stratified squamous, non-keratinised - 
reproductive - female labia majora Stratified squamous, keratinised - 
reproductive - male tubuli recti Simple cuboidal germinal epithelium (male) 
reproductive - male rete testis Simple cuboidal - 
reproductive - male ductuli efferentes Pseudostratified columnar - 
reproductive - male epididymis Pseudostratified columnar, with stereocilia - 
reproductive - male vas deferens Pseudostratified columnar - 
reproductive - male ejaculatory duct Simple columnar - 
reproductive - male (gland) bulbourethral glands Simple columnar - 
reproductive - male (gland) seminal vesicle Pseudostratified columnar - 
respiratory oropharynx Stratified squamous, non-keratinised - 
respiratory larynx Pseudostratified columnar, ciliated respiratory epithelium 
respiratory trachea Pseudostratified columnar, ciliated respiratory epithelium 
respiratory respiratory bronchioles Simple cuboidal - 
sensory cornea Stratified squamous, non-keratinised corneal epithelium 
sensory nose Pseudostratified columnar olfactory epithelium 
urinary kidney - proximal convoluted tubule Simple columnar, ciliated - 
urinary kidney - ascending thin limb Simple squamous - 
urinary kidney - distal convoluted tubule Simple columnar, non-ciliated - 
urinary kidney - collecting duct Simple cuboidal - 
urinary renal pelvis Transitional urothelium 
urinary ureter Transitional urothelium 
urinary urinary bladder Transitional urothelium 
urinary prostatic urethra Transitional urothelium 
urinary membranous urethra Pseudostratified columnar, non-ciliated - 
urinary penile urethra Pseudostratified columnar, non-ciliated - 
urinary external urethral orifice Stratified squamous - 


[edit] Cell junctions
Main article: Cell junction
A cell junction is a structure within a tissue of a multicellular organism. Cell junctions are especially abundant in epithelial tissues. They consist of protein complexes and provide contact between neighbouring cells, between a cell and the extracellular matrix, or they built up the paracellular barrier of epithelia and control the paracellular transport.


[edit] Secretory epithelia
As stated above, secretion is one major function of epithelial cells. Glands are formed from the invagination / infolding of epithelial cells and subsequent growth in the underlying connective tissue. There are two major classification of glands: endocrine glands and exocrine glands. Endocrine glands are glands that secrete their product directly onto a surface rather than through a duct. This group contains the glands of the Endocrine system


[edit] Embryology
Generally, there are epithelial tissues deriving from all of the embryological germ layers:

from ectoderm (e.g., the epidermis); 
from endoderm (e.g., the lining of the gastrointestinal tract); 
from mesoderm (e.g., the inner linings of body cavities). 
However, it is important to note that pathologists do not consider endothelium and mesothelium (both derived from mesoderm) to be true epithelium. This is because such tissues present very different pathology. For that reason, pathologists label cancers in endothelium and mesothelium sarcomas, while true epithelial cancers are called carcinomas. Also, the filaments that support these mesodermally derived tissues are very distinct. Outside of the field of pathology, the idea that epithelium arise from all three germ layers is generally accepted.


[edit] Additional images



 


[edit] Links
Parietal cell antibody 
Antibody to GPC 
An Example (cholesteatoma) 

[edit] References
Molecular Biology of the Cell, 4th edition, Alberts et al., 2002 
[show]v • d • eBiological tissue 
Animals Epithelium - Connective - Muscular - Nervous 
Plants Dermal - Vascular - Ground 
[show]v • d • eHistology: epithelial tissue 
Types Columnar (simple, stratified) - Cuboidal (simple, stratified) - Pseudostratified/Respiratory - Squamous (simple, stratified) - Transitional - Olfactory 
Features Lateral/cell-cell: Tight junction - Adherens junction - Desmosome - Gap junction
Basal/cell-matrix: Basal lamina - Hemidesmosome - Focal adhesion
Apical: Cilia - Microvilli - Stereocilia 
[show]v • d • etissue layers 
mesothelium, serosa/adventitia, muscularis externa (outer & inner), submucosa, mucosa (muscularis mucosa, lamina propria, epithelium), lumen 

Retrieved from "http://en.wikipedia.org/wiki/Epithelium"
Category: Tissues
Epithelial tissues are widespread throughout the body. They form the covering of all body surfaces, line body cavities and hollow organs, and are the major tissue in glands. They perform a variety of functions that include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception. 
Eukaryotes have areas inside the cell separated off from the rest of the cell by membranes, like the cell membrane (see below). These areas include the nucleus, numerous mitochondria and other organelles such as the golgi body, and or chloroplasts within each of their cells. These areas are made distinct from the main mass of the cells cytoplasm by their own membrane in order to allow them to be more specialised. You can think of them as separate rooms within your house. The nucleus contains all the cell's DNA, the Mitochondria are where energy is generated, chloroplasts are where plants trap the suns energy in photosynthesis. There are exceptions to every rule of course, and in this case the most obvious two are the red blood cells of animals and the sieve tube elements of plants, which, though living, have no nucleus and no DNA, normally these cells to do not live very long.
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Extracellular matrix
From Wikipedia, the free encyclopedia

 
Illustration depicting extracellular matrix (basement membrane and interstitial matrix) in relation to epithelium, endothelium and connective tissueIn biology, the extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.

Extracellular matrix includes the interstitial matrix and the basement membrane.[1] Interstitial matrix is present between various cells (i.e., in the intercellular spaces) . Gels of polysaccharides and fibrous proteins fill the interstitial space and act as a compression buffer against the stress placed on the ECM.[2] Basement membranes are sheet-like depositions of ECM on which various epithelial cells rest.

Contents [hide]
1 Role and importance 
2 Molecular components 
2.1 Proteoglycan matrix components 
2.1.1 Heparan sulfate proteoglycans 
2.1.2 Chondroitin sulfate proteoglycans 
2.1.3 Keratan sulfate proteoglycans 
2.2 Non proteoglycan matrix components 
2.2.1 Hyaluronic acid 
2.2.2 Collagen 
2.2.3 Fibronectin 
2.2.4 Elastin 
2.2.5 Laminin 
3 Cell adhesion to the ECM 
4 Cell types involved in ECM formation 
5 Extracellular matrix in plants 
6 References 
7 External links 
 


[edit] Role and importance
Due to its diverse nature and composition, the ECM can serve many functions, such as providing support and anchorage for cells, segregating tissues from one another, and regulating intercellular communication. The ECM regulates a cell's dynamic behavior. In addition, it sequesters a wide range of cellular growth factors, and acts as a local depot for them.[1] Changes in physiological conditions can trigger protease activities that cause local release of such depots. This allows the rapid and local growth factor-mediated activation of cellular functions, without de novo synthesis.

Formation of the extracellular matrix is essential for processes like growth, wound healing and fibrosis. An understanding of ECM structure and composition also helps in comprehending the complex dynamics of tumor invasion and metastasis in cancer biology[1] as metastasis often involves the destruction of extracellular matrix[3] by enzymes such as serine and Threonine proteases and Matrix metalloproteinase.[1]


[edit] Molecular components
Components of the ECM are produced intracellularly by resident cells, and secreted into the ECM via exocytosis.[4] Once secreted they then aggregate with the existing matrix. The ECM is composed of an interlocking mesh of fibrous proteins and glycosaminoglycans (GAGs).


[edit] Proteoglycan matrix components
GAGs are carbohydrate polymers and are usually attached to extracellular matix proteins to form proteoglycans (hyaluronic acid is a notable exception, see below). Proteoglycans have a net negative charge that attracts water molecules, keeping the ECM and resident cells hydrated. Proteoglycans may also help to trap and store growth factors within the ECM.

Described below are the different types of proteoglycan found within the extracellular matrix.


[edit] Heparan sulfate proteoglycans
For more details on this topic, see Heparan sulfate.
Heparan sulfate (HS) is a linear polysaccharide found in all animal tissues. It occurs as a proteoglycan (PG) in which two or three HS chains are attached in close proximity to cell suface or extracellular matrix proteins.[5][6] It is in this form that HS binds to a variety of protein ligands and regulates a wide variety of biological activities, including developmental processes, angiogenesis, blood coagulation and tumour metastasis.

In the extracellular matrix, especially basement membranes, the multi-domain proteins perlecan, agrin and collagen XVIII are the main proteins to which heparan sulfate is attached.


[edit] Chondroitin sulfate proteoglycans
For more details on this topic, see Chondroitin sulfate.
Chondroitin sulfates contribute to the tensile strength of cartilage, tendons, ligaments and walls of the aorta.


[edit] Keratan sulfate proteoglycans
For more details on this topic, see Keratan sulfate.
Keratan sulfates have a variable sulfate content and unlike many other GAGs, does not contain uronic acid. It is present in the cornea, cartilage, bones and the horns of animals.


[edit] Non proteoglycan matrix components

[edit] Hyaluronic acid
For more details on this topic, see Hyaluronic acid.
Hyaluronic acid (or "hyaluronan") is a polysaccharide consisting of alternative residues of D-glucuronic acid and N-acetylglucosamine, and unlike other GAGs is not found as a proteoglycan. Hyaluronic acid in the extracellular space confers upon tissues the ability to resist compression by providing a counteracting turgor (swelling) force by absorbing alot of water. Hyaluronic acid is thus found in abundance in the ECM of load-bearing joints. It is also a chief component of the interstitial gel. Hyaluronic acid is found on the inner surface of the cell membrane and is translocated out of the cell during biosynthesis.[7]

Hyaluronic acid acts as an environmental cue that regulates cell behavior during embryonic development, healing processes, inflamation and tumor development. It interacts with a specific transmembrane receptor, CD44.[8]


[edit] Collagen
For more details on this topic, see Collagen.
Collagens are, in most animals, the most abundant glycoproteins in the ECM. In fact, collagen is the most abundant protein in the human body[9][10] and accounts for 90% of bone matrix protein content.[11] Collagens are present in the ECM as fibrillar proteins and give structural support to resident cells. Collagen is exocytosed in precursor form (procollagen), which is then cleaved by procollagen proteinases to allow extracellular assembly. Diseases such as osteogenesis imperfecta and epidermolysis bullosa are linked with genetic defects in collagen-encoding genes.[4]


[edit] Fibronectin
For more details on this topic, see Fibronectin.
Fibronectins are proteins that connect cells with collagen fibers in the ECM, allowing cells to move through the ECM. Fibronectins bind collagen and cell surface integrins, causing a reorganization of the cell's cytoskeleton and facilitating cell movement. Fibronectins are secreted by cells in an unfolded, inactive form. Binding to integrins unfolds fibronectin molecules, allowing them to form dimers so that they can function properly. Fibronectins also help at the site of tissue injury by binding to platelets during blood clotting and facilitating cell movement to the affected area during wound healing.[4]


[edit] Elastin
For more details on this topic, see Elastin.
Elastins, in contrast to collagens, give elasticity to tissues, allowing them to stretch when needed and then return to their original state. This is useful in blood vessels, the lungs and in skin, and these organs contain high amounts of elastins. Elastins are synthesized by fibroblasts and smooth muscle cells. Elastins are highly insoluble, and tropoelastins are secreted inside a chaperone molecule, which releases the precursor molecule upon contact with a fiber of mature elastin. Tropoelastins are then deaminated to become incorporated into the elastin strand. Diseases such as cutis laxa and Williams syndrome are associated with deficient or absent elastin fibers in the ECM.[4]


[edit] Laminin
For more details on this topic, see Laminin.
Laminins are proteins found in the basal laminae of virtually all animals. Rather than forming collagen-like fibers, laminins form networks of web-like structures that resist tensile forces in the basal lamina. They also assist in cell adhesion. Laminins bind other ECM components such as collagens, nidogens, and entactins.[4]


[edit] Cell adhesion to the ECM
Many cells bind to components of the extracellular matrix. This cell-to-ECM adhesion is regulated by specific cell surface cellular adhesion molecules (CAM) known as integrins. Integrins are cell surface proteins that bind cells to ECM structures, such as fibronectin and laminin, and also to integrin proteins on the surface of other cells.

Fibronectins bind to ECM macromolecules and facilitate their binding to transmembrane integrins. The attachment of fibronectin to the extracellular domain initiates intracellular signaling pathways as well as association with the cellular cytoskeleton via a set of adaptor molecules such as actin.[2]


[edit] Cell types involved in ECM formation
There are many cell types that contribute to the development of the various types of extracellular matrix found in plethora of tissue types. The local components of ECM determine the properties of the connective tissue.

Fibroblasts are the most common cell type in connective tissue ECM, in which they synthesize, maintain and provide a structural framework; fibroblasts secrete the precursor components of the ECM, including the ground substance. Chondrocytes are found in cartilage and produce the cartilagenous matrix. Osteoblasts are responsible for bone formation.


[edit] Extracellular matrix in plants
Plant cells are tesselated to form tissues. The cell wall is the relatively rigid structure surrounding the plant cell. The cell wall provides lateral strength to resist osmotic turgor pressure, but is flexible enough to allow cell growth when needed; it also serves as a medium for intercellular communication. The cell wall comprises multiple laminate layers of cellulose microfibrils embedded in a matrix of glycoproteins such as hemicellulose, pectin, and extensin. The components of the glycoprotein matrix help cell walls of adjacent plant cells to bind to each other. The selective permeability of the cell wall is chiefly governed by pectins in the glycoprotein matrix. Plasmodesmata (singular: plasmodesma) are pores that traverse the cell walls of adjacent plant cells. These channels are tightly regulated and selectively allow molecules of specific sizes to pass between cells.[7]


[edit] References
^ a b c d Kumar, Abbas, Fausto; Robbins and Cotran: Pathologic Basis of Disease; Elsevier; 7th ed. 
^ a b Alberts B, Bray D, Hopin K, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2004). "Tissues and Cancer", Essential cell biology. New York and London: Garland Science. ISBN 0-8153-3481-8.  
^ Liotta LA, Tryggvason K, Garbisa S, Hart I, Foltz CM, Shafie S (1980). "Metastatic potential correlates with enzymatic degradation of basement membrane collagen". Nature 284 (5751): 67–8. PMID 6243750.  
^ a b c d e Plopper G (2007). The extracellular matrix and cell adhesion, in Cells (eds Lewin B, Cassimeris L, Lingappa V, Plopper G). Sudbury, MA: Jones and Bartlett. ISBN 0-7637-3905-7.  
^ Gallagher, J.T., Lyon, M. (2000). "Molecular structure of Heparan Sulfate and interactions with growth factors and morphogens", in Iozzo, M, V.: Proteoglycans: structure, biology and molecular interactions. Marcel Dekker Inc. New York, New York, 27-59.  
^ Iozzo, R. V. (1998). "Matrix proteoglycans: from molecular design to cellular function". Annu. Rev. Biochem. 67: 609-652. PMID 9759499.  
^ a b Lodish H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipursky SL, Darnell J. Molecular Cell Biology, 5th, New York: WH Freeman and Company, 197–234.  
^ Peach et al 1993. Identification of hyaluronic acid binding sites in the extracellular domain of CD44. The Journal of Cell Biology, Vol 122, 257-264 
^ Di Lullo GA, Sweeney SM, Korkko J, Ala-Kokko L, San Antonio JD (2002). "Mapping the ligand-binding sites and disease-associated mutations on the most abundant protein in the human, type I collagen". J. Biol. Chem. 277 (6): 4223–31. DOI:10.1074/jbc.M110709200. PMID 11704682.  
^ Karsenty G, Park RW (1995). "Regulation of type I collagen genes expression". Int. Rev. Immunol. 12 (2-4): 177–85. PMID 7650420.  
^ Kern B, Shen J, Starbuck M, Karsenty G (2001). "Cbfa1 contributes to the osteoblast-specific expression of type I collagen genes". J. Biol. Chem. 276 (10): 7101–7. DOI:10.1074/jbc.M006215200. PMID 11106645.  

[edit] External links
MeSH Extracellular+matrix 
ANAT3231 Lecture 08 Extracellular Matrix - Lecture about extracellular matrix from UNSW Cell Biology website. 
Extracellular matrix: review of its roles in acute and chronic wounds 
Usage of Extracellular Matrix from pigs to regrow human extremities 
"The Extracellular Matrix of Animals", from Chapter 19 of The Molecular Biology of the Cell, 4th edition, Alberts et al. 
 Lesson 4
FUNCTIONS OF THE INTEGUMENTARY SYSTEM

3-15. INTRODUCTION

The integumentary system forms the outermost covering of the human body. Thus, it is the boundary between the organism and the ambient (surrounding) environment. Because of this relationship, the integumentary system has a number of functions related to the environment and the individual's reactions to the environment.

3-16. REDUCTION OF FRICTION AND ITS EFFECTS

Over time, the body is likely to rub against many varied objects. The resulting frictional forces would be expected to damage the body surface. For comparison, consider the outer surfaces of older automobiles and other man-made objects.

Hairs. Hairs minimize friction by allowing surfaces to slip or slide over each other.

Outer Dead Cells. Where there is no hair (glabrous condition), the outer dead squamous cells rub off to reduce frictional forces. Within a couple of weeks after they arrive at the surface, the outer dead cells are removed during the activities of daily life.

Thickening of the Integument. The dermis and epidermis tend to become thicker whenever they are subjected to forces of pressures greater than average. Callouses are an extreme example of this.

3-17. WATERPROOFING

The outer layers of dead horny cells are kept flexible by oil from the sebaceous glands. Thus, these layers form an essentially waterproof covering for the body. This is very important in preventing general dehydration of the body. Dehydration (water loss) is a very important problem in burn patients who have lost a full thickness of the integument.

3-18. PROTECTION FROM SOLAR RADIATION

The integument also protects the body from excessive penetration of solar radiation. Solar radiation is blocked by pigments (para 3-10) and by the layers of dead horny cells.

3-19. GENERAL SENSIBILITY

Not the least of the functions of the integument is its general sensibility. As the interface between the organism and the immediate environment, the integument is subjected to many stimuli. A number of general sensory receptor organs are located in the integument and the underlying subcutaneous layer. These receptor organs continuously inform the brain of the conditions immediately surrounding the body. These conditions include pain, temperature, light and heavy pressures, touch, and so forth.
 
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0902.jpg]]

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0902.jpg]]


9-14. PRIMARY SEX ORGAN--OVARY

The ovary is the primary sex organ (gonad) of the female. 

Location. Each female has a pair of ovaries, located in the pelvic cavity. Each ovary is attached to the posterior aspect of the broad ligament on its respective side of the uterus. 
Production of the Ovum. One female gamete (ovum) is released per menstrual cycle (about 28 days). 
(1)  Within an ovary, one of the germinal cells begins to develop and grows larger as it stores food material. This development takes place within a follicle, a fluid-filled cavity within the ovary. 
(2)  At midperiod, the mature ovum is expelled from the follicle onto the surface of the ovary. The free ovum is picked up by the uterine tube. (para 9-1 5a). 
Production of Female Sex Hormones. Initially, the cells of the ovary that form the follicle secrete the hormones called estrogens. After the ovum has been expelled from the follicle, the resulting cavity is filled with a yellowish material known as the corpus luteum. The corpus luteum secretes primarily progesterone, a hormone that helps prepare the uterus for pregnancy. Thus, estrogens are secreted during the first half of the menstrual cycle, and progesterone is added during the second half of the period. This pattern of hormone secretion is a major factor in the menstrual cycle. 
9-15. SECONDARY SEX ORGANS

The secondary sex organs of the female serve to transport and care for the ovum and to develop the new individual (embryo and fetus). 

Uterine Tube (Oviduct, Fallopian Tube). The uterine tube picks up the free ovum when it is expelled from the follicle of the ovary. The ovum stays in the uterine tube to await fertilization. If it is fertilized, it goes through the initial stages of embryonic development, and the embryo then passes on to the uterus. On the other hand, if it is not fertilized, its stored food is exhausted in 3 to 5 days; it dies and its remains are absorbed by the uterine tube. 
Uterus. The uterus is a single pear-shaped organ located within the pelvic cavity of the female. The early embryo passes into the uterus from the uterine tube. The embryo continues its development within the uterus. 
(1)  Endometrium. The inner lining of the uterus is known as the endometrium. The endometrium is an epithelium containing uterine glands and blood vessels. Under the influence of the estrogens and progesterone, the embryo present at the end of the menstrual cycle, the endometrium breaks down. (This produces a "flow" of blood and cellular elements (menses) in a process known as menstruation.) 
(2)  Amniotic sac and placenta. When the embryo passes into the uterine cavity from the uterine tube, it "burrows" into the endometrium. Later, a fluid-filled sac (the amniotic sac) surrounds the embryo. The embryo floats free, surrounded by amniotic fluid. The embryo has an umbilical cord that originates in the center of its anterior abdomen. The umbilical cord is attached to the wall of the uterus by a special structure known as the placenta. 
(3  Cervix. The cervix, the inferior end of the uterus, is inserted into the top of the vagina. Through the center of the cervix is the cervical canal. Its wall consists primarily of circular muscle tissue, which holds the opening closed until time for parturition (giving birth). During the initial stage of parturition, the cervical musculature dilates (stretches) to form an opening for the passage of the newborn (to be). 
Vagina. The vagina is a tubular structure that extends from the cervix of the uterus to the exterior of the perineum. After the vagina receives the male penis, the semen is discharged into the upper recess opposite the opening of the cervix. At parturition, the vagina forms the birth canal through which the newborn passes to the outside. 
External Genitalia. The opening of the vagina and of the urethra are covered by the external genitalia. Included among the external genitalia are two pairs of folds--the major and minor labia. Also included is the clitoris, a small structure comparable to the male penis but without the urethra. 
9-16. SECONDARY SEXUAL CHARACTERISTICS

The secondary sexual characteristics of the female are those features designed to make a female attractive to the male. These features include a higher-pitched voice, hair distribution, and body softness and shape.

9-17. THE FEMALE BONY PELVIS

The female bony pelvis is an important consideration in childbirth. 

Several studies have been concerned with the spatial relationships of the female bony pelvis. One of the most extensive is the Caldwell-Moloy Classification of Female Pelvis. This study categorizes female pelvis by shape. It illustrates those types that are better and those that are less well suited for childbirth. 
Just before childbirth, the phenomenon of "relaxation" occurs. In this phenomenon, the ligaments of the bony pelvis and perineum become quite stretchable. This increases the diameters of the birth canal. 
9-18. THE MAMMARY GLAND

The mammary glands are cutaneous glandular structures of the female. 

Location. The mammary glands are located in the upper pectoral regions. On occasion, a mammary gland may be found elsewhere along the "milk line." The milk line extends from the axilla above to the inguinal region below. 
Structure. Each mammary gland is made up of glandular tissue and associated ducts. These structures are embedded in FCT and fat. 
Lactation. During pregnancy, the mammary glands respond to the estrogens and progesterone with additional growth. Toward the end of pregnancy, it begins to form a fluid substance, colostrum. Within 2 or 3 days after the baby is born, the breasts begin to secrete large quantities of milk instead of colostrum. 
Importance of Nursing. One cannot overemphasize the importance of nursing (breast-feeding) the newborn. 
(1)  Human milk is the natural food of the newborn infant. 
(2)  Strong psychological effects accompany nursing. This is true for both the child and the mother. 
(3)   Initially after childbirth, the mammary gland secretes colostrum. Colostrum is not primarily a food item. In fact, the baby loses birth weight. Colostrum consists most importantly of antibodies that protect the newborn during the first 6 months of life. 
(4)  A baby may develop an upper respiratory infection. During suckling, it will inject some of the microorganisms into the milk ducts of the mammary gland. By the next feeding, the mammary gland has produced the antibodies appropriate for that infection. 
Self-Examination. The female breast (mammary gland) is often a location for tumor growth. Thus, it is important for a woman to be able to examine her own breasts. During this self-examination, she must remember that a portion of the breast extends up into the axilla. (This portion is called the "axillary tail.") 
Fermentation (biochemistry)
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For other uses, see Fermentation.
 
Fermentation in progressFermentation is a process of energy production in a cell under anaerobic conditions (with no oxygen required). In common usage fermentation is a type of anaerobic respiration, however a more strict definition exists which defines fermentation as respiration under anaerobic conditions with no external electron acceptor. Fermentation does not necessarily have to be carried out in an anaerobic environment, however. For example, even in the presence of abundant oxygen, yeast cells greatly prefer fermentation to oxidative phosphorylation, as long as sugars are readily available for consumption [1].

Sugars are the common substrate of fermentation, and typical examples of fermentation products are ethanol, lactic acid, and hydrogen. However, more exotic compounds can be produced by fermentation, such as butyric acid and acetone. Yeast famously carries out fermentation in the production of ethanol in beers, wines and other alcoholic drinks, along with the production of large quantities of carbon dioxide. Anaerobic respiration in mammalian muscle under periods of intense exercise (which has no external electron acceptor) is, under the strict definition, a type of fermentation.

Contents [hide]
1 History 
2 Reaction 
3 Energy source in anaerobic conditions 
4 Products 
5 Enzymology 
6 See also 
7 References 
8 External links 
 


[edit] History
French chemist Louis Pasteur was the first zymologist, when in 1857 he connected yeast to fermentation. Pasteur originally defined fermentation as respiration without air.

Pasteur performed careful research and concluded, "I am of the opinion that alcoholic fermentation never occurs without simultaneous organization, development and multiplication of cells.... If asked, in what consists the chemical act whereby the sugar is decomposed ... I am completely ignorant of it.".

The German Eduard Buchner, winner of the 1907 Nobel Prize in chemistry, later determined that fermentation was actually caused by a yeast secretion that he termed zymase.

The research efforts undertaken by the Danish Carlsberg scientists greatly accelerated the gain of knowledge about yeast and brewing. The Carlsberg scientists are generally acknowledged with jump-starting the entire field of molecular biology.fermention is CO2+nutrions=energy


[edit] Reaction
See also: glycolysis 
The reaction of fermentation differs according to the sugar being used and the product produced. Below the sugar will be glucose (C6H12O6) the simplest sugar, and the product will be ethanol (2C2H5OH). This is one of the fermentation reactions carried out by yeast, and is used in food production.

Chemical Equation

C6H12O6 + 2Pi + 2ADP- → 2CH3CH2OH + 2CO2 + 2 ATP (Energy Released:118 kJ/mol) 
Word Equation

Sugar (glucose or fructose) → Alcohol (ethanol) + Carbon Dioxide + Energy (ATP) 
The actual biochemical pathway the reaction takes varies depending on the sugars involved, but commonly involves part of the glycolysis pathway, which is shared with the early stages of aerobic respiration in most organisms. The later stages of the pathway vary considerably depending on the final product.


[edit] Energy source in anaerobic conditions
Fermentation is thought to have been the primary means of energy production in earlier organisms before oxygen was at high concentration in the atmosphere and thus would represent a more ancient form of energy production in cells.

Fermentation products contain chemical energy (they are not fully oxidized) but are considered waste products since they cannot be metabolized further without the use of oxygen (or other more highly-oxidized electron acceptors). A consequence is that the production of ATP by fermentation is less efficient than oxidative phosphorylation, where pyruvate is fully oxidized to carbon dioxide. Fermentation produces two ATP molecules per molecule of glucose compared to 38 by aerobic respiration: 8 are produced from FADH2, and 30 are produced from NADH, for a total of 38.

Aerobic glycolysis is a method employed by muscle cells for the production of lower-intensity energy over a longer period of time when oxygen is plentiful. Under low-oxygen conditions, however, vertebrates use the less-efficient but faster anaerobic glycolysis to produce ATP. The speed at which ATP is produced is about 100 times that of oxidative phosphorylation.[citation needed] While fermentation is helpful during short, intense periods of exertion, it is not sustained over extended periods in complex aerobic organisms. In humans, for example, lactic acid fermentation provides energy for a period ranging from 30 seconds to 2 minutes.

The final step of fermentation, the conversion of pyruvate to fermentation end-products, does not produce energy. However, it is critical for an anaerobic cell since it regenerates nicotinamide adenine dinucleotide (NAD+), which is required for glycolysis. This is important for normal cellular function, as glycolysis is the only source of ATP in anaerobic conditions.


[edit] Products
Products produced by fermentation are actually waste products produced during the reduction of pyruvate to regenerate NAD+ in the absence of oxygen. Bacteria generally produce acids. Vinegar (acetic acid) is the direct result of bacterial metabolism (Bacteria need oxygen to convert the alcohol to acetic acid). In milk, the acid coagulates the casein, producing curds. In pickling, the acid preserves the food from pathogenic and putrefactive bacteria.

When yeast ferments, it breaks down the glucose (C6H12O6) into exactly two molecules of ethanol (C2H6O) and two molecules of carbon dioxide (CO2).

Ethanol fermentation (performed by yeast and some types of bacteria) breaks the pyruvate down into ethanol and carbon dioxide. It is important in bread-making, brewing, and wine-making. When the ferment has a high concentration of pectin, minute quantities of methanol can be produced. Usually only one of the products is desired; in bread the alcohol is baked out, and in alcohol production the carbon dioxide is released into the atmosphere. 
Lactic acid fermentation breaks down the pyruvate into lactic acid. It occurs in the muscles of animals when they need energy faster than the blood can supply oxygen. It also occurs in some bacteria and some fungi. It is this type of bacteria that converts lactose into lactic acid in yogurt, giving it its sour taste. 
In vertebrates, during intense exercise, cellular respiration will deplete oxygen in the muscles faster than it can be replenished. An associated burning sensation in muscles has been attributed lactic acid causing a decrease in the pH during a shift to anaerobic glycolysis. While this does partially explain acute muscle soreness, lactic acid may also help delay muscle fatigue[citation needed], although, eventually the lower pH will inhibit enzymes involved in glycolysis.[citation needed] Contrary to currently popular belief, the lactic acid is not the primary causes for the drop in pH, but rather ATP-derived hydrogen ions.[citation needed]

Delayed onset muscle soreness cannot be attributed to the lactic acid and other waste products as they are quickly removed after exercise. It is actually due to microtrauma of the muscle fibres. Eventually the liver metabolizes the lactic acid back to pyruvate.

Hydrogen gas is produced in many types of fermentation (mixed acid fermentation, butyric acid fermentation, caproate fermentation, butyric acid fermentation, butanol fermentation, glyoxylate fermentation), as a way to regenerate NAD+ and FAD from NADH and FADH2. Electrons are transferred to ferredoxin, which in turn is oxidized by hydrogenase, producing H2. Hydrogen gas is a substrate for methanogens and sulphate reducers, who keep the concentration of hygdrogen sufficiently low to allow the production of such an energy-rich compound. [2]

Some anaerobic eukaryotic microorganisms also produce hydrogen gas, in their hydrogenosomes. The concentration of hydrogen gas is kept low by symbionts such as methanogens that reside in the cytosol of the eukaryot.[2]


[edit] Enzymology
Enzymology is the scientific term for yeast oriented fermentation. It deals with the biochemical processes involved in fermentation, with yeast selection and physiology, and with the practical issues of brewing. Enzymology is occasionally known as zymology or zymurgy.


[edit] See also
Fermentation (food) 
Industrial fermentation 
Fermentation lock 
Fed-batch 
Chemostat 
Ethanol fermentation 

[edit] References
^ Dickinson, J. R. (1999). Carbon metabolism. In: The Metabolism and Molecular Physiology of Saccharomyces cerevisiae, ed. J. R. Dickinson and M. Schweizer, Philadelphia, PA: Taylor & Francis. 
^ a b Madigan, Martinko, Brock Biology of Microorganisms, 11th ed 

[edit] External links
The chemical logic behind fermentation and respiration 
Inline disintegration to reduce fermentation time and improve the yield 
[hide]v • d • eMetabolism: carbohydrate metabolism 
Fermentation (Ethanol, Lactic acid) - Glycolysis/Gluconeogenesis - Glycogenesis/Glycogenolysis - Pentose phosphate pathway - Photosynthesis (Carbon fixation) Carbohydrate catabolism 

Retrieved from "http://en.wikipedia.org/wiki/Fermentation_%28biochemistry%29"
Categories: Articles to be merged since June 2007 | Articles needing additional references from April 2007 | All articles with unsourced statements | Articles with unsourced statements since February 2007 | Oenology | Fermented beverages | Brewing | Food science | Metabolism | Food preservation | Alchemical processes | Fermentation | Microbiology | Mycology

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There are four main tissue types in the body: epithelial, connective, muscle, and nervous.
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<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5119523333884690578"><img src="http://lh3.google.com/cardwell.bob/RwwzWQeFQJI/AAAAAAAABZI/q2X91HE8A14/s800/skelant.jpg" /></a></html>
 Lesson 2
GAMETES (SEX CELLS)

9-8. INTRODUCTION

Within the genetic makeup of each individual, there is a pair of chromosomes known as the sex chromosomes. There are two kinds of such chromosomes--X and Y.

9-9. MEIOSIS

Within the gonads, there is a special type of cell division known as meiosis. The usual set of chromosomes is reduced in this reduction division. Thus, the gametes (ova or spermatozoa) have only a single set of chromosomes.

9-10. FERTILIZATION

In the final analysis, the production of a new individual is based upon the union of the male gamete (spermatozoon) with the female gamete (ovum). This process is called fertilization. At this time, a double set of chromosomes is reconstituted. 

If the zygote (fertilized egg) has two X chromosomes, the individual will be female (XX). 
If the zygote has one X and one Y chromosome, the individual will be male 
(XY).
 
Lesson 10
GENERAL ADAPTATIONS FOR GRASPING/HOLDING

3-39. INTRODUCTION

The hands grasp or hold onto things. The soles of the feet provide a nonslipping contact with the ground. For these reasons, frictional forces are maximized in the palms of the hands and the soles of the feet. This is accomplished by several adaptations of the coverings of the body in these areas.

3-40. ADAPTATIONS

These adaptations are described below: 

The epidermis and dermis are quite thickened in these areas. 
These two areas are hairless (glabrous). 
The dermal papillae holding the dermis and epidermis together are increased in number and size. 
The surface of the skin has many ridges and grooves. These, in effect, form miniature suction cups. 
Deep in the palm and sole, there is a very dense FCT, referred to as the palmar aponeurosis and plantar aponeurosis. A thickened subcutaneous layer firmly attaches the modified integument to the underlying aponeurosis. 
GENERAL SENSORY PATHWAYS OF THE HUMAN NERVOUS SYSTEM
 Lesson 7
12-22. INTRODUCTION TO PATHWAYS

A pathway of the human nervous system is the series of neurons or other structures used to transmit an item of information. In general, we consider two major types of pathways-the general sensory pathways and the motor pathways. 

Ascent or Descent Through the Neuraxis. The general sensory pathways ascend through the neuraxis to the brain. The motor pathways descend through the neuraxis from the brain. The neuraxis includes both the spinal cord and the brainstem. The pathways are included in various fiber tracts of the neuraxis. 

Crossing to the Opposite Side (Decussation). At some specific level in the neuraxis, all of these pathways cross to the opposite side of the midline of the CNS. (Each crossing is called a decussation.) Thus, the right cerebral hemisphere of the brain communicates with the left half of the body. The left cerebral hemisphere communicates with the right half of the body. 

12-23. INTRODUCTION TO GENERAL SENSORY PATHWAYS 

The General Senses. The general senses detect those specific stimuli which are received throughout the body (general distribution). When these general senses are perceived at the conscious level (in the cerebral cortex), they are known as sensations. The general senses of humans include pain, touch, temperature, and proprioception ("body sense"). 

Neurons of a General Sensory Pathway. A general sensory pathway extends from the point where the stimulus is received to the postcentral gyrus of the cerebral hemisphere (para 12-6c(3)(c)). The postcentral gyrus is the site of conscious sensation of a stimulus. Between the point of stimulus reception and the postcentral gyrus, there is a minimum of three neurons in series. 

(1) The first neuron is the afferent (sensory) neuron. It picks up the information from the sensory receptor organ and carries it to the CNS via the appropriate peripheral nerves. 
(2) The second neuron is the interneuron, located within the spinal cord or brainstem. It crosses the midline of the CNS to the opposite side. It then ascends the neuraxis to the forebrainstem, where it reaches a mass of gray matter called the thalamus. In the thalamus, the interneuron synapses with the cell body of the third neuron. 
(3)  The axon of the third neuron projects up through the cerebral hemisphere to the appropriate location in the postcentral gyrus. 

Homunculus of Conscious Sensations. There is a specific location in the postcentral gyrus which corresponds to each location in the body. For example, a location in the postcentral gyrus near the midline of the brain (at the top of the cerebral hemisphere) receives information from the hip region. On the other hand, information from the tongue and the pharynx projects to the lowest part of the postcentral gyrus, just above the lateral sulcus. 

Visceral Sensory Inputs. Visceral sensory inputs follow pathways different from those of other general sensory pathways. The inputs for visceral reflex actions usually travel via the parasympathetic nerves. The visceral inputs for pain usually travel via the sympathetic nerves. 
12-24. PAIN--A GENERAL SENSE

Pain is an ancient protective mechanism which generally helps us to avoid injury. However, tolerance for pain varies from one individual to another. 

Means of Reducing Pain (Analgesia). 
(1)  Endorphins ("morphine from within"). Endorphins are chemicals found naturally within the body which tend to block the sensation of pain. 
(2) Drugs. Clinically, a number of drugs are used to block or reduce the sensation of pain. 
(3) Competing inputs. Competing pain stimuli tend to minimize each other. The body usually recognizes one pain stimulus at a time. Thus, an individual may "bite his lip" when he anticipates a painful experience. 

Pain Receptor. The pain receptor is not a specific receptor organ, as with most senses. This receptor is referred to as a free nerve ending. 

Excessive Stimulation. If any of the other senses receives excessive stimulus, pain results. Examples are excessive light and excessive noise. 

Pain Reflex Arc. Generally, a pain sensory input causes a reflex action long before the information reaches the cerebral cortex and the pain is consciously perceived. For example, you will remove your hand from a hot object before you realize you have been burned. 

Pathway for Conscious Sensation of Pain. As usual, the pathway leading to conscious sensation of pain consists of three neurons. 

(1) The first neuron is the afferent (sensory) neuron from the free nerve ending. Within the CNS, it synapses with the interneuron. 
(2) The axon of the interneuron crosses to the opposite side of the CNS. It then ascends the neuraxis in a fiber tract known as the lateral spinothalamic tract. This tract is found in the lateral funiculus (see Figure 12-6). In the thalamus, the interneuron synapses with the third neuron. 
(3) The third neuron projects to the appropriate location of the postcentral gyrus of the cerebral hemisphere. Here, this information is interpreted or recognized as a pain sensation from a particular part of the body. 


12-25. TEMPERATURE -- GENERAL SENSES

There are two categories of temperature in the body--warmth and cold. 

However, these are relative entities. For example, a given temperature seems cool when compared to a much higher temperature and seems hot when compared to a much lower temperature. 
In addition, the body has two different mechanisms for sensing temperature. 
(1) Specific sensory receptors detect warmth and especially cold in the periphery of the body. 
(2) Special heat-sensitive neurons in the hypothalamus detect increases in the temperature of the blood that flows through the hypothalamus (portion of the forebrainstem). By this means, the body monitors the core temperature, the temperature in the central part of the body. 
Neurons for the general sense of temperature use pathways similar to those discussed for pain (para 12-24e). They include both nerves and fiber tracts. 

12-26. TOUCH -- GENERAL SENSES

Throughout the body are a variety of sensory receptors which detect varying degrees of pressure. For example, the pacinian corpuscles are typical of the receptors which detect deep pressure. In addition, an individual can usually identify the location of a touch on his body; in fact, he can usually distinguish two simultaneous touches to adjacent areas (the "two-touch test"). As usual with the general senses, sensory inputs for touch can also result in immediate reflex actions. 

Pathway for Conscious Sensation of Light Touch. 
(1) The pathway for the conscious sensation of light touch begins with the usual afferent (sensory) neuron as the first neuron. The afferent neuron carries the information to the CNS by way of the appropriate nerve. 
(2)  In the CNS, the afferent neuron synapses with the interneuron, the second neuron of the pathway. After crossing to the opposite side of the CNS, the interneuron ascends the neuraxis in the fiber tract known as the anterior spinothalamic tract. This is in the anterior funiculus of the spinal cord (Figure 12-6). 
(3) In the thalamus, the second neuron synapses with the third neuron. The axon of the third neuron then projects to the appropriate location in the postcentral gyrus of the cerebral hemisphere. There, it is interpreted as the conscious sensation, light touch. 

Pathway for Conscious Sensation of Deep Touch. The pathway for deep touch is quite different from that for light touch. 

(1) Still, the first neuron is the afferent neuron from the deep touch receptor to the CNS via the appropriate nerve. When the axon of the afferent neuron enters the CNS, it turns upward and ascends the neuraxis in the posterior funiculus (Figure 12-6) of the same side that it entered. In other words, it does not yet cross the midline of the CNS. 
(2)  In the lower hindbrainstem, the axon of the first neuron synapses with the cell body of the second neuron. The axon of the second neuron then crosses to the opposite side of the brainstem. This axon then continues the ascent through the neuraxis to the thalamus, where it synapses with the third neuron. 
(3)  Again, the axon of the third neuron projects to the appropriate location in the postcentral gyrus of the cerebral hemisphere. There, impulses are interpreted as conscious sensations of deep touch. 


12-27. "BODY SENSE" 

General. Body sense is the combined information from a number of sensory inputs. Second by second, these inputs keep the brain informed of the specific posture of the body and its parts. Some of the senses involved include: 

Muscle sense (proprioception). Joint capsule sense. 
Integument senses. 
Special senses (eye, ear, etc.). 
Proprioception (Muscle Sense). 

(1) For proprioception, there is a very special receptor organ to monitor the degree of stretch of the muscle. These receptor organs, called muscle spindles or stretch receptors, are distributed within the fleshy belly of each skeletal muscle. In effect, the muscle spindles are parallel to striated muscle fibers of the skeletal muscles. Therefore, as the muscle fibers contract or are stretched, the muscle spindle detects relative muscle length. 
(a)   The afferent neuron from the muscle spindle is known as the annulospiral neuron because its terminal is coiled. Due to this coiling, it is a spring-like apparatus which can be stretched or compressed according to the condition of the muscle. The annulospiral neuron travels to the CNS by way of the appropriate nerve. It continuously carries information about the specific state of the muscle. 
(b)   An annulospiral neuron from a muscle in one of the limbs, in particular, synapses directly on the motor neuron that carries commands back to the same muscle. This motor neuron is called the alpha motor neuron. Together, the annulospiral neuron and the alpha motor neuron make up the stretch (monosynaptic) reflex. Due to this reflex, there is a proportionate increase in the tension of a muscle as it stretches. 

(2) Another stretch receptor associated with the skeletal muscle is the Golgi tendon organ. As its name implies, this organ is located within the tendon of the muscle. The Golgi tendon organ is located in the tendon near its attachment to the muscle fibers. Thus, it detects relative muscle tension. Its threshold is higher than that of the muscle spindles; in other words, there must be proportionately more contraction before it puts out a signal. Thus, when the muscle has been stretched excessively and might be subject to injury, its afferent neuron carries the message to the CNS. This results in relaxation of the muscle. 

(3) The pathway for the conscious sensation of these stretches uses the same structures as the deep touch general sense.  
Lesson 1
INTRODUCTION

13-1. GENERAL VERSUS SPECIAL SENSES 

The human body is continuously bombarded by all kinds of stimuli. Certain of these stimuli are received by sense organs distributed throughout the entire body. These are referred to as the general senses. 
Certain other stimuli (table 13-1) are received by pairs of receptor organs located in the head. These are the special senses. 
SPECIAL SENSE RECEPTOR ORGAN STIMULUS 
Sight (vision) bulbus oculi (eye) light rays 
Hearing (audition) ear (cochlea) sound waves 
Balance (equilibrium) ear (membranous labyrinth) gravity 
Smell (olfaction) olfactory hair cells in nose airborne molecules 
Taste (gustation) taste buds in mouth fluid-borne molecules 

Table 13-1. The special senses. 

Since the general senses respond to immediate contact, they are very short range. In contrast, the special senses are long range. 
13-2. INPUT TO BRAIN

From the special sense organs, information is sent to the brain through specific cranial nerves. When this information reaches specific areas of the cerebral cortex, the sensations are perceived at the conscious level.
<html><strong>An Action Plan for Helping those with Mental Illness</strong>

<img src="http://photos1.blogger.com/img/261/2778/1024/englehart2.1.jpg">
<strong>Sad, but true....</strong>



This is a plan for family members helping those with mental illness in Marion County, Indiana, or the Greater Indianapolis area. Please go <a href="http://www.psychlaws.org/JoinUs/CatalystArchive/CatalystSpringSummer2005.htm">here</a> to read about some suggestions from a general standpoint or to find some ideas for your area.

My basic belief is that whenever possible, those with mental illness should take the responsibility for their own care.  However, mental illness often robs individuals of their judgment and it becomes necessary for family and the community to intercede for the safety of the individual and the community.

I would like to start off with two names of the most knowledgeable and caring persons I know on matters of mental health. These persons are: <strong>Mike Trent</strong>, of Midtown Mental Health Center [ph 317- 630-7791] and  <strong>Judy Spray</strong>, of the PAIR Mental Health Diversion Program  [317- 327-6869]. I would certainly start with these two for ideas and guidance on helping a love one into treatment.

If he is dangerous to himself or others, the family can seek an <a href="http://www.psychlaws.org/LegalResources/StateLaws/Indianastatute.htm">Emergency Detention </a>to a mental health center.  After a period of 72hrs, the hospital has to determine if he is dangerous as a result of mental illness. If so, the hospital can have him court ordered for long term inpatient or outpatient treatment. This procedure must be initiated in cooperation with a mental health center as the petition for an emergency detention must have a doctor's statement, as well as a factual witness, and the agreement of the mental health center that they will hospitalize the person for a period of observation. There may be a fee charged by the mental health center for this service. Some mental health centers serving Indianapolis are:

<a href="http://www.wishard.edu/internet/midtown/">Midtown MHC</a>

<a href="http://www.ecommunity.com/behavioralcare/index.asp?pg=6363">Gallahue MHC/Community Hospital </a>

<a href="http://www.behaviorcorp.com/locations/location.asp">BehaviorCorp.</a>

<a href="http://www.adultchild.org/">Adult and Child MHC</a>

<a href="http://www.in.gov/fssa/servicemental/faq/2cchild&adoles.html">Assorted Mental Health Providers</a>

If the mentally ill person presents an immediate danger, one can always call <strong>911</strong> and explain that there is a mentally ill person in need who may harm themselves or others. The mentally ill person can be picked up by the responsible law enforcement officer and taken to the nearest appropriate treatment facility under provisions of the <a href="http://www.in.gov/legislative/ic/code/title12/ar26/ch4.html">Immediate Detention Law</a>. Another strategy is to avoid calling 911, if time and circumstances permit, and call the shift commander of the appropriate law enforcement district. This may permit the commander the time to exercise more judgment and discretion on what officers to send out and at what time. Working with caring law enforcement officers may lessen the trauma to the mentally ill person and facilitate the person gaining appropriate access to the right services. A mission of the Indianapolis law enforcement agencies are to encourage the notion of "community policing" and the problem of the mentally ill falls under this plan. To find the appropriate officer in your area, go to <a href="http://www.indygov.org/eGov/City/DPS/IPD/home.htm">IPD here</a> or the <a href="http://www.indygov.org/eGov/County/MCSD/home.htm">MCSD here. </a> 
If he is gravely disabled, the family can go to <a href="http://www6.indygov.org/clerk/probate/">Probate Court </a>and seek Guardianship over him.  The court or his guardian can then sign him in for treatment. You will need to start with an attorney first.
 
If he has any pending criminal charges [probation, parole, court case], the court, parole officer, or probation officer can order him into treatment. IF he is in custody, <a href="http://www.indygov.org/eGov/County/MCSD/contactus.htm">email</a> or call [317-231-8263], the jail and request that he be evaluated for treatment while in custody. It would also be advisable to notify the <a href="http://www.mentalhealthcourtsurvey.com/IN.asp">PAIR Mental Health Diversion Program</a>, at 317-327-6869, and request an evaluation.
 
If he is a nuisance, the family, or any responsible party, can go to court and ask for a <a href="http://www.indygov.org/eGov/County/Pros/FAQ/Protect/home.htm">protective order</a>. The court can order him to quit being a nuisance to the petitioner and order him into treatment. To get a protective order one has to go through the <a href="http://www.indygov.org/eGov/County/Pros/FAQ/Protect/home.htm">Marion Co. Prosecutor's Office </a>and be a resident of the county. This person also has to be the offended party. There may be a charge for filing the petition.A person may qualify for <a href="http://www.popbp.org/boardmem.htm">free assistance </a>in getting a protective order.
 
If the family has the means, they can hire an attorney for help. <strong>Steven Eichholtz</strong> is an excellent attorney who use to be the mental health court judge. He can be reached at:

Steve Eichholtz 
Locke Reynolds, LLP
201 N. Illinois Street
Indianapolis,
Indiana 46204
(317) 237-3800 Bus.
seichholtz@locke.com 


<strong><a href="http://pview.findlaw.com/view/1490309_1?noconfirm=0&channel=LP">Mike Grubbs</a></strong> and <strong><a href="http://www.google.com/local?hl=en&lr=&rls=GGLD,GGLD:2004-50,GGLD:en&q=John+Christ+attorney&near=Indianapolis,+IN&sa=X&oi=locald&radius=0.0&latlng=39768333,-86158055,2060282948075979837">John Christ </a></strong>are two other attorneys who have experience in mental health matters.

Two well known local legal minds also have extensive knowledge about mental health issues. They are <strong><a href="http://www.iclu.org/who_we_are/">Ken Falk</a></strong> and <a href="http://www.iclu.org/"><strong>Fran Quigley</strong>, both of the ICLU</a>.
 
Finally, if all of the above doesn't work out, get an advocate. All of the mental health centers and courts are political entities who depend on funding and the good will of the public. You would be surprised how much a phone call from an advocate will help with your cause. Just look up the phone numbers, web addresses,  or location; then write or call, but follow up and expect a response.  Here are some possible advocates in no particular order:
 
<a href="http://www.in.gov/ipas/">Protection and Advocacy Agency of Indiana</a>
or specifically with mental health treatment issues, <a href="http://www.in.gov/ipas/priorities/paimi.html">go here</a>.

<a href="http://www.mcmha.org/">Marion Co. Mental Health Association</a>

<a href="http://www.in.gov/fssa/elderly/aging/aps.html">Adult Protective Services</a>

<a href="http://www.namiindiana.org/">NAMI- National Alliance of the Mentally Ill</a>

<a href="http://www.psychlaws.org/">TAC- Treatment Advocacy Center</a>

<a href="http://www.in.gov/legislative/legislators/">State Representatives</a>

<a href="http://www.congressmerge.com/onlinedb/cgi-bin/newseek.cgi?site=congressmerge&state=in">Federal Representatives</a>

<strong>Judge Evan Goodman</strong>, Marion County Superior Court
[Mental Health Expert and Advocate]
Court 15 
City-County Bldg. Room W-343
3rd Floor, West Wing
(317) 327-3229

<strong>Judge Barb Collins</strong>, Marion County Superior Court
[Mental Health Expert and Advocate]
Court 8 
City-County Bldg Room E-643
6th Floor, East Wing
(317) 327-3202

<a href="http://www.indygov.org/eGov/Mayor/mac.htm">Mayor </a>

<a href="http://www.in.gov/gov/contact.html">Governor</a>

<a href="http://www.wishtv.com/global/story.asp?s=2186293&ClientType=Printable">Misc. Helpful Indiana Resources</a>
 
Read about The <a href="http://www.bobcardwell.com/PAIRWEB.html">PAIR Mental Health Diversion Program here</a>.

Read about mental health laws across the country <a href="http://www.psychlaws.org/LegalResources/Index.htm">here.</a>

I worked a lot on this web page today. Later I did a <a href="http://www.google.com/search?hl=en&lr=&q=PAIR+Mental+Health+Diversion+Program">google search </a>in RE: to PAIR and there is an <a href="http://www.bobcardwell.com/letterepair.jpg">article</a> appearing in the paper. Must be <strong>synchronicity</strong>!!</html>
Glycolysis
From Wikipedia, the free encyclopedia
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See also: Gluconeogenesis which carries out a process where glucose is synthesized rather than catabolized. 
The word glycolysis is derived from Greek γλυκύς (sweet) and λύσις (rupture). It is the initial process of most carbohydrate catabolism, and it serves three principal functions:

The generation of high-energy molecules (ATP and NADH) as cellular energy sources as part of anaerobic and aerobic respiration. This process in the cell can have oxygen present and sometimes may not. 
Production of pyruvate for the citric acid cycle as part of aerobic respiration. 
The production of a variety of six- and three-carbon intermediate compounds, which may be removed at various steps in the process for other cellular purposes. 
As the foundation of both aerobic and anaerobic respiration, glycolysis is the archetype of universal metabolic processes known and occurring (with variations) in many types of cells in nearly all organisms. Glycolysis, through anaerobic respiration, is the main energy source in many prokaryotes, eukaryotic cells devoid of mitochondria (e.g. mature erythrocytes) and eukaryotic cells under low oxygen conditions (e.g. heavily exercising muscle or fermenting yeast).

In eukaryotes and prokaryotes, glycolysis takes place within the cytoplasm of the cell. In plant cells some of the glycolytic reactions are also found in the kevin-Benson cycle which functions inside the chloroplasts. The wide conservation includes the most phylogenetically deep rooted extant organisms and thus it is considered to be one of the most ancient metabolic pathways.[1]

The most common and well-known type of glycolysis is the Embden-Meyerhof pathway, initially explained by Gustav Embden and Otto Meyerhof. The term can be taken to include alternative pathways, such as the Entner-Doudoroff Pathway. However, glycolysis will be used here as a synonym for the Embden-Meyerhof pathway.

Contents [hide]
1 Overview 
2 Discovery 
3 Sequence of reactions 
3.1 Preparatory phase 
3.2 Pay-off phase 
3.3 Oxidative decarboxylation 
4 Regulation 
4.1 Hexokinase 
4.2 Phosphofructokinase 
4.3 Pyruvate kinase and phosphoglycerate kinase 
5 Post-glycolysis processes 
5.1 Aerobic respiration 
5.2 Anaerobic respiration 
5.3 Intermediates for other pathways 
6 Glycolysis in disease 
6.1 Genetic diseases 
6.2 In cancer 
7 Alternative nomenclature 
8 See also 
9 External links 
10 References 
 


[edit] Overview
The overall reaction of glycolysis is:

 
D-Glucose    Pyruvate  
 + 2 NAD+ + 2 ADP + 2 Pi  2  + 2 NADH + 2 H+ + 2 ATP + 2 H2O 
 




 v • d • e Glycolysis Metabolic Pathway 
Glucose   Glucose-6-phosphate   Fructose 6-phosphate   Fructose 1,6-bisphosphate   Dihydroxyacetone phosphate  Glyceraldehyde 3-phosphate    Glyceraldehyde 3-phosphate    
 ATP ADP     ATP ADP           NAD+ + Pi NADH + H+ 
    +  2  
            NAD+ + Pi NADH + H+ 
 1,3-Bisphosphoglycerate    3-Phosphoglycerate    2-Phosphoglycerate    Phosphoenolpyruvate    Pyruvate    Acetyl-CoA 
  ADP ATP        H2O   ADP ATP   CoA + NAD+ NADH + H+ + CO2   
2  2  2  2  2  2 
 ADP ATP      H2O        
 

The products all have vital cellular uses:

ATP provides an energy source for many cellular functions. 
NADH + H+ provides reducing power for other metabolic pathways or further ATP synthesis. 
Pyruvate is used in the citric acid cycle in aerobic respiration to produce more ATP, or is converted to other small carbon molecules in anaerobic respiration. 
For simple anaerobic fermentations, the metabolism of one molecule of glucose to two molecules of pyruvate has a net yield of two molecules of ATP. Most cells will then carry out further reactions to 'repay' the used NAD+ and produce a final product of ethanol or lactic acid. Many bacteria use inorganic compounds as hydrogen acceptors to regenerate the NAD+.

Cells performing aerobic respiration synthesize much more ATP, but not as part of glycolysis. These further aerobic reactions use pyruvate and NADH + H+ from glycolysis. Eukaryotic aerobic respiration produces approximately 34 additional molecules of ATP for each glucose molecule, however most of these are produced by a vastly different mechanism to the substrate-level phosphorylation in glycolysis.

The lower energy production, per glucose, of anaerobic respiration relative to aerobic respiration results in greater flux through the pathway under hypoxic (low oxygen) conditions, unless alternative sources of anerobically oxidizable substrates, such as fatty acids, are found.


[edit] Discovery
The first formal studies of the glycolytic process were initiated in 1860 when Louis Pasteur discovered that microorganisms were responsible for fermentation, and in 1897 when Eduard Buchner found certain cell extracts could cause fermentation. The next major contribution was from Arthur Harden and William Young in 1905 who determined that a heat sensitive high molecular weight subcellular fraction (the enzymes) and a heat insensitive low molecular weight cytoplasm fraction (ADP, ATP and NAD+ and other cofactors) were required together for fermentation to proceed. The details of the pathway itself were eventually determined by 1940, with a major input from Otto Meyerhof and some years later by Luis Leloir. The biggest difficulties in determining the intricacies of the pathway were due to the very short lifetime and low steady-state concentrations of the intermediates of the fast glycolytic reactions.

  This short section requires expansion. 


[edit] Sequence of reactions
These are the major reactions, through which most glucose will pass. There are additional alternative pathways and regulatory products which are not shown here.


[edit] Preparatory phase
The first five steps are regarded as the preparatory (or investment) phase since they consume energy to convert the glucose into two three-carbon sugar phosphates (G3P).

The first step in glycolysis is phosphorylation of glucose by a family of enzymes called hexokinases to form glucose 6-phosphate. This reaction consumes ATP, but it acts to keep the glucose concentration low, promoting continuous transport of glucose into the cell through the plasma membrane transporters. In addition it blocks the glucose leaking out - the cell lacks transporters for glucose 6-phosphate. Glucose may alternatively be from the hydrolysis of intracellular starch or glycogen. 
In animals an isozyme of hexokinase called glucokinase is also used in the liver, which has a much lower affinity for glucose (km in the vicinity of normal glycemia), and differs in regulatory properties. The different substrate affinity and alternate regulation of this enzyme are a reflection of the role of the liver in maintaining blood sugar levels.

Cofactors: Mg2+
 D-Glucose (Glc) Hexokinase (HK)
a transferase α-D-Glucose-6-phosphate (G6P) 
    
ATP ADP 
 
  
  
    
 




G6P is then rearranged into fructose 6-phosphate by glucose phosphate isomerase. Fructose can also enter the glycolytic pathway by phosphorylation at this point. 
The change in structure is an isomerization, in which the G6P has been converted to fructose 6-phoshpate, (F6P). The reaction requires a catalytic enzyme, phosphohexose isomerase, to procede. This reaction is freely reversible under normal cell conditions. However, it is often driven forward because of a low concentration of fructose 6-phosphate, which is constantly consumed during the next step of glycolysis. Under conditions of high fructose 6-phosphate concentration this reaction readily runs in reverse. This phenomenon can be explained through Le Chatelier's Principle.
 α-D-Glucose 6-phosphate (G6P) Phosphoglucose isomerase
an isomerase β-D-Fructose 6-phosphate (F6P) 
    
  
 
  
  
    
 




The energy expenditure of another ATP in this step is justified in 2 ways: the glycolytic process (up to this step) is now irreversible, and the energy supplied destabilizes the molecule. Because the reaction catalyzed by PFK-1 is energetically very favorable it is essentially irreversible and a different pathway must be used to do the reverse conversion during gluconeogenesis. This makes the reaction a key regulatory point, see below. [During fasting the concentration of fructose 2,6-bisphosphate (an allosteric activator of PFK1) is low such that PFK1 activity is reduced. This leads to an increase of flux through the gluconeogenesis pathway.] 
Cofactors: Mg2+
 β-D-Fructose 6-phosphate (F6P) phosphofructokinase (PFK-1)
a transferase β-D-Fructose 1,6-bisphosphate (F1,6BP) 
    
ATP ADP 
 
  
  
    
 




Destabilizing the molecule in the previous reaction allows the hexose ring to be split by aldolase into two triose sugars, dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. β-D-Fructose 1,6-bisphosphate (F1,6BP) fructose bisphosphate aldolase (ALDO)
a lyase D-glyceraldehyde 3-phosphate (GADP)  dihydroxyacetone phosphate (DHAP) 
   +  
  
 
  
 
     
 




triosephosphate isomerase rapidly interconverts dihydroxyacetone phosphate with glyceraldehyde 3-phosphate (GADP) that proceeds further into glycolysis. This is advantageous as it directs dihydroxyacetone phosphate down the same pathway as glyceraldehyde 3-phosphate, simplifying regulation. Dihydroxyacetone phosphate (DHAP) triosephosphate isomerase (TPI)
an isomerase D-glyceraldehyde 3-phosphate (GADP) 
    
  
 
  
  
    
 

Note - The third step can also be catalysed by pyrophosphate dependent phosphofructokinase (PFP or PPi-PFK). This enzyme catalyses the same reaction as PFK1 (also known as ATP-PFK), but uses pyrophosphate (PPi) as a phosphate donor instead of ATP. It is a reversible reaction, increasing the flexibility of glycolytic metabolism. This enzyme is not found in animal cells, but is found in most plants, some bacteria, archaea and protists.[2] A rarer ADP dependant PFK enzyme (ADP-PFK) variant has been identified in archaean species.[3] 

[edit] Pay-off phase
The second half of glycolysis is known as the pay-off phase, characterised by a net gain of the energy-rich molecules ATP and NADH. Since glucose leads to two triose sugars in the preparatory phase, each reaction in the pay-off phase occurs twice per glucose molecule. This yields 2 NADH molecules and 4 ATP molecules, leading to a net gain of 2 NADH molecules and 2 ATP molecules from the glycolytic pathway per glucose.

The triose sugars are dehydrogenated and inorganic phosphate is added to them, forming 1,3-bisphosphoglycerate. 
The hydrogen is used to reduce two molecules of NAD, a hydrogen carrier, to give NADH + H+.
 glyceraldehyde 3-phosphate (GADP) glyceraldehyde phosphate dehydrogenase (GAPDH)
an oxidoreductase D-1,3-bisphosphoglycerate (1,3BPG) 
    
NAD+ + Pi NADH + H+ 
 
NAD+ + Pi NADH + H+ 
  
    
 




This step is the enzymatic transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP by phosphoglycerate kinase, forming ATP and 3-phosphoglycerate. At this step, glycolysis has reached the break-even point: 2 molecules of ATP were consumed, and 2 new molecules have now been synthesized. This step, one of the two substrate-level phosphorylation steps, requires ADP; thus, when the cell has plenty of ATP (and little ADP) this reaction does not occur. Because ATP decays relatively quickly when it is not metabolized, this is an important regulatory point in the glycolytic pathway. 
Cofactors: Mg2+
 1,3-bisphosphoglycerate (1,3BPG) phosphoglycerate kinase (PGK)
a transferase 3-phosphoglycerate (3PG) 
    
ADP ATP 
 
ADP ATP 
  
  phosphoglycerate kinase (PGK)  
 




Phosphoglycerate mutase now forms 2-phosphoglycerate. Notice that this enzyme is a mutase and not an isomerase. While an isomerase changes the oxidation state of the carbons of the compound, a mutase does not. 3-phosphoglycerate (3PG) phosphoglycerate mutase (PGM)
a mutase 2-phosphoglycerate (2PG) 
    
  
 
  
  
    
 




Enolase next forms phosphoenolpyruvate from 2-phosphoglycerate. 
Cofactors: 2 Mg2+: one "conformational" ion to coordinate with the carboxylate group of the substrate, and one "catalytic" ion which participates in the dehydration.
 2-phosphoglycerate (2PG) enolase (ENO)
a lyase phosphoenolpyruvate (PEP) 
    
 H2O 
 
 H2O 
  
  enolase (ENO)  
 




A final substrate-level phosphorylation now forms a molecule of pyruvate and a molecule of ATP by means of the enzyme pyruvate kinase. This serves as an additional regulatory step, similar to the phosphoglycerate kinase step. 
Cofactors: Mg2+
 phosphoenolpyruvate (PEP) pyruvate kinase (PK)
a transferase pyruvate (Pyr) 
    
ADP ATP 
 
  
  
    
 


[edit] Oxidative decarboxylation
Main article: Pyruvate decarboxylation
This reaction is not technically a reaction of glycolysis, but is very common in most organisms as a link to the citric acid cycle. This reaction is carried out in the mitochondria, unlike the reactions of glycolysis which are cytosolic. 
The addition of Coenzyme A (CoA) to the pyruvate traps the product, acetyl CoA, within the mitochondria. This is analogous to the phosphorylation of glucose in the first step of glycolysis.
 pyruvate (Pyr) pyruvate dehydrogenase (PDHC) acetyl CoA (Ac-CoA) 
    
CoA + NAD+ CO2 + NADH + H+ 
 
  
  
    
 


[edit] Regulation
See also: Gluconeogenesis 
The flux through the glycolytic pathway is adjusted in response to conditions both inside and outside the cell. The rate is regulated to meet two major cellular needs: (1) the production of ATP, and (2) the provision of building blocks for biosynthetic reactions. In some cases the pathway may be halted entirely to allow the reverse process gluconeogenesis. In glycolysis, the reactions catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase are effectively irreversible in most organisms. In metabolic pathways, such enzymes are potential sites of control, and all these three enzymes serve this purpose in glycolysis.

There are several different ways to regulate the activity of an enzyme. An immediate form of control is feedback via allosteric effectors or by covalent modification. A slower form of control is transcriptional regulation that controls the amounts of these important enzymes.


[edit] Hexokinase
 
Yeast hexokinase B. PDB 1IG8.Hexokinase is inhibited by glucose-6-phosphate (G6P), the product it forms through the ATP driven phosphorylation. This is necessary to prevent an accumulation of G6P in the cell when flux through the glycolytic pathway is low. Glucose will enter the cell but since the hexokinase is not active it can readily diffuse back to the blood through the glucose transporter in the plasma membrane. If hexokinase remained active during low glycolytic flux the G6P would accumulate and the extra solute would cause the cells to enlarge due to osmosis.

In animals regulation of blood glucose levels by the liver is a vital part of homeostasis. In liver cells, any extra G6P is stored as glycogen. In these cells hexokinase is not expressed, instead glucokinase catalyses the phosphorylation of glucose to G6P. This enzyme is not inhibited by high levels of G6P and glucose can still be converted to G6P and then be stored as glycogen. This is important when blood glucose levels are high. During hypoglycemia the glycogen can be converted back to G6P and then converted to glucose by a liver specific enzyme glucose 6-phosphatase. This reverse reaction is an important role of liver cells to maintain blood sugars levels during fasting. This is critical for neuron function since they can only use glucose as an energy source.


[edit] Phosphofructokinase
 
Bacillus stearothermophilus phosphofructokinase. PDB 6PFK.Phosphofructokinase is an important control point in the glycolytic pathway since it is immediately downstream of the entry points for hexose sugars.

High levels of ATP inhibit the PFK enzyme by lowering its affinity for F6P. ATP causes this control by binding to a specific regulatory site that is distinct from the catalytic site. This is a good example of allosteric control. AMP can reverse the inhibitory effect of ATP. A consequence is that PFK is tightly controlled by the ratio of ATP/AMP in the cell. This makes sense since these molecules are direct indicators of the energy charge in the cell.

Since glycolysis is also a source of carbon skeletons for biosynthesis, a negative feedback control to glycolysis from the carbon skeleton pool is useful. Citrate is an example of a metabolite that regulates phosphofructokinase by enhancing the inhibitory effect of ATP. Citrate is an early intermediate in the citric acid cycle, and a high level means that biosynthetic precursors are abundant.

Low pH also inhibits phosphofructokinase activity and prevents the excessive rise of lactic acid during anaerobic conditions that could otherwise cause a drop in blood pH (acidosis), (a potentially life threatening condition).

Fructose 2,6-bisphosphate (F2,6BP) is a potent activator of phosphofructokinase (PFK-1) that is synthesised when F6P is phosphorylated by a second phosphofructokinase (PFK2). This second enzyme is inactive when cAMP is high, and links the regulation of glycolysis to hormone activity in the body. Both glucagon and adrenalin cause high levels of cAMP in the liver. The result is lower levels of liver fructose 2,6-bisphosphate such that gluconeogenesis (glycolysis in reverse) is favored. This is consistent with the role of the liver in such situations since the response of the liver to these hormones is to releases glucose to the blood.


[edit] Pyruvate kinase and phosphoglycerate kinase
 
Yeast pyruvate kinase. PDB 1A3W.Pyruvate kinase and phosphoglycerate kinase catalyze the two substrate-level phosphorylation steps, and produce ATP from ADP. The requirement of ADP to carry out this reaction provides regulation as when the cell has plenty of ATP it will have little ADP so this reaction is unable to happen. ATP decays relatively quickly, even when not used as an energy source, these stages provide the required simple and fast regulation of ATP levels.

This control is accentuated as, after the formation of F1,6bP, many of the glycolysis reactions are energetically unfavorable. The only reactions that are favorable are these two substrate-level phosphorylation steps. These two reactions pull the glycolytic pathway to completion when ADP is low and ATP is required.


[edit] Post-glycolysis processes
The ultimate fate of pyruvate and NADH produced in glycolysis depends upon the organism and the conditions, most notably the presence or absence of oxygen and other external electron acceptors. In addition, not all carbon entering the pathway leaves as pyruvate and may be extracted at earlier stages to provide carbon compounds for other pathways.


[edit] Aerobic respiration
Main article: Aerobic respiration 
In aerobic organisms, pyruvate typically enters the mitochondria where it is fully oxidized to carbon dioxide and water by pyruvate decarboxylase (oxidative decarboxylation) and the set of enzymes of the citric acid cycle. The products of pyruvate are sequentially dehydrogenated as they pass through the cycle, powering the reduction of NAD+ to NADH. In turn the NADH is ultimately oxidized by an electron transport chain using oxygen as final electron acceptor to produce a large amount of ATP via the action of the ATP synthase complex, a process known as oxidative phosphorylation. A small amount of ATP is also produced by substrate-level phosphorylation during the citric acid cycle.


[edit] Anaerobic respiration
Main article: Anaerobic respiration 
In animals, including humans, metabolism is primarily aerobic. However, under hypoxic (or partially anaerobic) conditions, for example in overworked muscles that are starved of oxygen or in infarcted heart muscle cells, pyruvate is converted to lactate by anaerobic respiration (also known as fermentation). This is a solution to maintaining the metabolic flux through glycolysis in response to an anaerobic or severely hypoxic environment. In many tissues this is a cellular last resort for energy, and most animal tissue cannot maintain anaerobic respiration for an extended length of time. Many single cellular organisms only use anaerobic respiration as an energy source.

Glycolysis is insufficient for anaerobic respiration, as it does not regenerate NAD+ from the NADH + H+ it produces. It is therefore critical for an anaerobic or hypoxic cell to carry out the additional steps of lactate or alcohol production to regenerate NAD+ that is required for glycolysis to proceed. This is important for normal cellular function, as glycolysis is the only source of ATP in anaerobic or severely hypoxic conditions.

There are several types of anaerobic respiration wherein pyruvate and NADH are anaerobically metabolized to yield any of a variety of products with an organic molecule acting as the final hydrogen acceptor. For example, the bacteria involved in making yogurt simply reduce pyruvate to lactic acid, whereas yeast produces ethanol and carbon dioxide. Anaerobic bacteria are capable of using a wide variety of compounds, other than oxygen, as terminal electron acceptors in respiration: nitrogenous compounds (such as nitrates and nitrites), sulphur compounds (such as sulphates, sulphites, sulphur dioxide, and elemental sulphur), carbon dioxide, iron compounds, manganese compounds, cobalt compounds, and uranium compounds.


[edit] Intermediates for other pathways
This article concentrates on the catabolic role of glycolysis with regard to converting potential chemical energy to usable chemical energy during the oxidation of glucose to pyruvate. However, many of the metabolites in the glycolytic pathway are also used by anabolic pathways, and, as a consequence, flux through the pathway is critical to maintain a supply of carbon skeletons for biosynthesis.

These metabolic pathways are all strongly reliant on glycolysis as a source of metabolites:

Gluconeogenesis 
Lipid metabolism 
Pentose phosphate pathway 
Citric acid cycle, which in turn leads to: 
Amino acid synthesis 
Nucleotide synthesis 
Tetrapyrrole synthesis 
From an energy perspective, NADH is either recycled to NAD+ during anaerobic conditions, to maintain the flux through the glycolytic pathway, or used during aerobic conditions to produce more ATP by oxidative phosphorylation. From an anabolic metabolism perspective, the NADH has a role to drive synthetic reactions, doing so by directly or indirectly reducing the pool of NADP+ in the cell to NADPH, which is another important reducing agent for biosynthetic pathways in a cell.


[edit] Glycolysis in disease

[edit] Genetic diseases
Glycolytic mutations are generally rare due to importance of the metabolic pathway, however some mutations are seen.

  This short section requires expansion. 


[edit] In cancer
Malignant rapidly-growing tumor cells typically have glycolytic rates that are up to 200 times higher than those of their normal tissues of origin. There are two common explanations. The classical explanation is that there is poor blood supply to tumors causing local depletion of oxygen. There is also evidence that attributes some of these high aerobic glycolytic rates to an overexpressed form of mitochondrially-bound hexokinase[4] responsible for driving the high glycolytic activity. This phenomenon was first described in 1930 by Otto Warburg, and hence it is referred to as the Warburg effect. Warburg hypothesis claims that cancer is primarily caused by dysfunctionality in mitochondrial metabolism, rather than because of uncontrolled growth of cells. There is ongoing research to affect mitochondrial metabolism and treat cancer by starving cancerous cells in various new ways, including a ketogenic diet.

This high glycolysis rate has important medical applications, as high aerobic glycolysis by malignant tumors is utilized clinically to diagnose and monitor treatment responses of cancers by imaging uptake of 2-18F-2-deoxyglucose (a radioactive modified hexokinase substrate) with positron emission tomography (PET).[5][6]


[edit] Alternative nomenclature
Some of the metabolites in glycolysis have alternative names and nomenclature. In part, this is because some of them are common to other pathways, such as the Calvin cycle.

 This article Alternative names Alternative nomenclature 
1 glucose Glc dextrose  
3 fructose 6-phosphate F6P   
4 fructose 1,6-bisphosphate F1,6BP fructose 1,6-diphosphate FBP, FDP, F1,6DP 
5 dihydroxyacetone phosphate DHAP glycerone phosphate  
6 glyceraldehyde 3-phosphate GADP 3-phosphoglyceraldehyde PGAL, G3P, GALP,GAP 
7 1,3-bisphosphoglycerate 1,3BPG glycerate 1,3-bisphosphate,
glycerate 1,3-diphosphate,
1,3-diphosphoglycerate PGAP, BPG, DPG 
8 3-phosphoglycerate 3PG glycerate 3-phosphate PGA, GP 
9 2-phosphoglycerate 2PG glycerate 2-phosphate  
10 phosphoenolpyruvate PEP   
11 pyruvate Pyr pyruvic acid  


[edit] See also
Pentose phosphate pathway 
Gluconeogenesis 
Fermentation (biochemistry) 

[edit] External links
The Glycolytic enzymes in Glycolysis at Protein Data Bank 
Glycolytic cycle with animations at wdv.com 
Metabolism, Cellular Respiration and Photosynthesis - The Virtual Library of Biochemistry and Cell Biology at biochemweb.org 
notes on glycolysis at rahulgladwin.com 
The chemical logic behind glycolysis at ufp.pt 
Expasy biochemical pathways poster at ExPASy 
Mnemonic at medicalmnemonics.com 317 5468 

[edit] References
^ Romano AH, Conway T. (1996) Evolution of carbohydrate metabolic pathways. Res Microbiol. 147(6-7):448-55 PMID 9084754 
^ Reeves, R. E.; South D. J., Blytt H. J. and Warren L. G. (1974). "Pyrophosphate: D-fructose 6-phosphate 1-phosphotransferase. A new enzyme with the glycolytic function 6-phosphate 1-phosphotransferase.". J Biol Chem 249: 7737–7741. PMID 4372217.  
^ Selig, M.; Xavier K. B., Santos H. and Schönheit P. (1997). "Comparative analysis of Embden-Meyerhof and Entner-Doudoroff glycolytic pathways in hyperthermophilic archaea and the bacterium Thermotoga.". Arch Microbiol 167: 217-232. PMID 9075622.  
^ High Aerobic Glycolysis of Rat Hepatoma Cells in Culture: Role of Mitochondrial Hexokinase -- Bustamante and Pedersen 74 (9): 3735 -- Proceedings of the National Academy of Sciences. Retrieved on December 5, 2005. 
^ PET Scan: PET Scan Info Reveals .... Retrieved on December 5, 2005. 
^ 4320139 549..559. Retrieved on December 5, 2005. 
 This article is of interest to the Metabolic Pathways WikiProject. 
You can help us improve and organize this article. 

[show]v • d • eCellular Respiration 
Aerobic Respiration Glycolysis → Pyruvate Decarboxylation → Citric Acid Cycle → Oxidative Phosphorylation (Electron Transport Chain + ATP synthase) 
Anaerobic Respiration Glycolysis → Lactic Acid Formation or Ethanol Formation 
[show]v • d • eMetabolism: carbohydrate metabolism 
Fermentation (Ethanol, Lactic acid) - Glycolysis/Gluconeogenesis - Glycogenesis/Glycogenolysis - Pentose phosphate pathway - Photosynthesis (Carbon fixation) Carbohydrate catabolism 
[show]v • d • eMetabolism map 

Glucuronate metabolismPentose interconversionInositol metabolismCellulose and sucrose
metabolismStarch and glycogen
metabolismOther sugar
metabolismPentose phosphate pathwayGlycolysis and GluconeogenesisAmino sugars metabolismSmall amino acid synthesisBranched amino acid
synthesisPurine biosynthesisHistidine metabolismAromatic amino
acid synthesisPyruvate
decarboxylationAnaerobic
respirationFatty acid
metabolismUrea cycleAspartate amino acid
group synthesisPorphyrins and
corrinoids
metabolismCitric acid cycleGlutamate amino
acid group
synthesisPyrimidine biosynthesis v • d • e  All pathway labels on this image are links, simply click to access the article. 
 A high resolution labeled version of this image is available here.  
 
[show]v • d • eCarbohydrate metabolism: glycolysis/gluconeogenesis enzymes 
Glycolysis Glucokinase/Hexokinase/Glucose 6-phosphatase - Glucose isomerase - Phosphofructokinase 1/Fructose 1,6-bisphosphatase - Aldolase - Triosephosphate isomerase - Glyceraldehyde 3-phosphate dehydrogenase - Phosphoglycerate kinase - Phosphoglycerate mutase - Enolase - Pyruvate kinase 
Gluconeogenesis only Pyruvate carboxylase - Phosphoenolpyruvate carboxykinase - from lactate (Cori cycle): Lactate dehydrogenase - from alanine (Alanine cycle): Alanine transaminase 
Regulatory Phosphofructokinase 2/Fructose 2,6-bisphosphatase - Bisphosphoglycerate mutase 


Retrieved from "http://en.wikipedia.org/wiki/Glycolysis"
Categories: Glycolysis | Articles with sections needing expansion | Cellular respiration | Metabolic pathways | Carbohydrates

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 Lesson 3
HOMEOSTASIS

2-10. INTRODUCTION

a. The body fluids play an important role in homeostasis. Homeostasis is the body's tendency to maintain a steady state. The tissue fluid forms the immediate environment of the living cell. In order to maintain the life processes of the individual cells, there must be appropriate concentrations of oxygen, carbon dioxide, nutrients, electrolytes, and other substances within the tissue fluid.

b. One of the chief functions of any organ system is to help to maintain this steady state. For example, the digestive system helps to maintain a steady concentration of nutrients. The respiratory system helps to maintain steady concentrations of oxygen and the removal of carbon dioxide.

c. All organ systems are at least partially controlled by a feedback mechanism. A feedback mechanism resembles the household thermostat. When the concentration of a substance is too low, the feedback mechanism stimulates an increased production and/or distribution. Once the level returns to normal, the feedback mechanism signals a decrease in production. There is a similar feedback mechanism for body temperature.

2-11. WATER BALANCE

The body has a natural requirement for a certain amount of water to continue its processes properly. Lack of fluid in the circulatory system can result in heart failure. Excessive amounts of fluid in the tissue spaces cause swelling of the body, known as edema. There are feedback mechanisms to maintain water balance.

2-12. ELECTROLYTE BALANCE

The electrolytes must also be in balance. Electrolyte balance is an important consideration when fluids are administered to a patient. See Figure 2-3 for an explanation of tonicity.


[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0203.jpg]]
Figure 2-3. Tonicity (cell with semipermeable membrane, nonpermeable to electrolytes present).

a. Hypertonicity. If the overall concentration of electrolytes is greater in the tissue fluid surrounding a cell than it is in the intracellular fluid within the cell, the tissue fluid is hypertonic (noun: hypertonicity). The cell tends to be destroyed by loss of its fluid to the hypertonic environment.

b. Hypotonicity. If the overall concentration of electrolytes as less in the tissue fluid than it is in the intracellular fluid within the cell, the tissue fluid is hypotonic (noun: hypotonicity). In a hypotonic environment, fluid will enter a cell and cause it to swell and burst.

c. Isotonicity. If the concentrations of electrolytes are the same in the tissue fluid and the intracellular fluid, the situation is balanced (homeostatic). That is, the fluids are isotonic.

 

2-13. MOVEMENT OF MATERIALS INTO AND OUT OF THE CELL

We noted earlier that all substances that enter or leave the cell must pass through the cell membrane in some way.

a. Semipermeability. The permeability of a membrane is its capacity to allow materials to move through it. Since the cell membrane of animal cells is selective and does not allow all materials to pass through it, we say that it is semipermeable (noun: semipermeability).

b. Diffusion. Some materials readily pass through the membrane from an area of higher concentration to an area of lower concentration. This process is called diffusion. When materials require help to pass through the cell membrane, the process is referred to as facilitated diffusion.

c. Active Transport. In certain situations, materials pass through the cell membrane against the concentration gradient. In this case, an expenditure of energy is required. The process is called active transport. An example is the sodium/potassium pump, in which the sodium ions are forced out of the cytoplasm of the cell and into the surrounding tissue fluid and potassium ions are pumped back into the cell cytoplasm.

d. Osmosis. Sometimes a substance is not able to pass through the cell membrane. When the concentration of this substance is greater on one side of the cell membrane than the other, water will tend to pass through the membrane to the area of greater concentration. This process is called osmosis. This process involves the concept of tonicity, discussed in paragraph 2-12.

e. Pinocytosis and Phagocytosis. Sometimes, the cell membrane will engulf a minute amount of tissue fluid and its contents. This process is called pinocytosis. During pinocytosis, the cell membrane produces a vacuole to contain the engulfed material. When the cell membrane engulfs larger particles, such as bacteria or other cells, the process is called phagocytosis. After either pinocytosis or phagocytosis, digestive fluids may pass from the cytoplasm into the vacuole. The end products of digestion are absorbed from the vacuole into the cell cytoplasm.

 

2-14. MEMBRANE POTENTIALS

In living cells, there is generally a higher concentration of positively charged ions on the outside of the cell and a higher concentration of negatively charged ions on the inside of the cell. Thus, there is a concentration gradient (an electrical potential or polarity) across the membrane that we call the membrane potential that creates an electrical gradient.

a. Resting Potential. When the cell is in a resting state, the membrane potential is maintained by the sodium/potassium pump. The sodium/potassium pump actively transports 3 positive sodium ions (Na+) to the outside of the cell membrane and 2 potassium ions to the inside of the cell membrane. This results in a negative charge inside the cell and a positive charge outside the cell, producing a potential or polarity across the membrane.

b. Action Potential. The electrical activity that occurs in a stimulated neuron or muscle fiber is called the action potential. This involves depolarization and subsequent repolarization. First, sodium ions move into the cell by diffusion. This reverses the polarity (depolarization). Second, potassium moves out of the cell by diffusion that causes repolarization. The sodium/potassium pump then restores the ionic balance by actively (energy required) pumping sodium back out and potassium back into the cell. These various electrical potentials can be measured with appropriate instruments.
 
 14-1. INTRODUCTION 

Heredity. With respect to both anatomy and physiology, offspring tend to resemble their parents. This is due to the process known as heredity or inheritance. Heredity depends upon the passage of materials called genes from one generation to the next. Due to genes, all human beings resemble each other in general, but with individual differences. 
Genetic Control. The genes control the life processes of each body cell. In an individual, each cell has identical genes. Overall, genes determine the range of potentiality of an individual, and the environment develops it. For example, good nutrition will help a person to attain his full body height and weight within the limits determined by his genes. 
14-2. HISTORY OF GENETICS 

Over a hundred years ago, the Austrian monk Gregor Mendel began the science of genetics by experimenting with successive generations of peas. He originated the concepts of genes, dominance, and recessiveness. By choosing the simplest and most straightforward situations, he set forth the basic principles of inheritance. However, his work was not well known for many years. 
With the turn of the century, the principles of genetics were "rediscovered," particularly by the Dutch biologist Hugo de Vries. In the following years, the principles of genetics were further developed by the American, T. H. Morgan. 
In 1944, Oswald T. Avery and his colleagues used bacterial studies to prove that DNA was the genetic substance of chromosomes. 
In 1954, Watson and Crick published the double helix model of DNA. (A helix is a spiral form.) 
Three Frenchmen, Jacob, Lwoff, and Monod, discovered how information is transmitted from the genes to the sites of protein synthesis. This led to the "cracking" of the genetic code, used to translate DNA patterns for the production of specific proteins. 
14-3. THE GENE

DNA (deoxyribonucleic acid) is a large molecule consisting of two strands in a double-helix arrangement. Along each strand are specific chemical elements called nucleotides. Each gene consists of a portion of a strand, including a number of nucleotides. Through the arrangement of its nucleotides, the gene provides coded information for the construction of proteins. After these proteins are assembled elsewhere in the cell, they serve as building blocks for the cell and as enzymes to promote the life processes of the cell.

14-4. CHROMOSOMES 

A chromosome is a very long double-helix thread of DNA. Thus, each chromosome consists of a large number of genes. The genes have very specific locations along the length of each chromosome. Recently, researchers have been able to identify specific sequences of genes along a chromosome and illustrate the sequences with gene maps. 
Except during cell division, chromosomes are observed as granules of chromatin material within the cell nucleus. During the process of cell division, this chromatin material aggregates so that it may be identified as one of the 46 individual chromosomes found in each human cell (diploid condition). 
These 46 chromosomes of the human cell occur in pairs. Thus, we may say that there are two sets, with 23 chromosomes in each set. 
(22 + 1) X 2 = 46

Of the 23 different chromosomes, 22 deal with the body in general and are called autosomal chromosomes. The last chromosome is called the sex chromosome. There are two kinds of sex chromosomes--X and Y. When an individual's cells each have two X chromosomes (XX), the individual is genetically a female. On the other hand, when an individual's cells each have one X and one Y chromosome (XY), that individual is genetically a male.

14-5. CELL DIVISIONS

The two types of cell division are illustrated in figure 14-1. 

Mitosis. New cells must be produced for replacement of worn-out cells and for growth and development of the individual. For these purposes, the existing cells undergo cell division and produce new cells. The usual process of cell division is called mitosis. In mitosis, the two daughter cells produced by the original cell have essentially the same genetic material as the original cell. 
Meiosis. Meiosis is a type of cell division which occurs only in the gonads. It results in the formation of the gametes, or sex cells. In mitosis, the chromosomes are duplicated; in meiosis, the two sets of chromosomes separate, and one set of 23 goes to each of the gametes. Thus, meiosis involves a reduction division. The final result is that each gamete has only one set of 23 chromosomes (haploid condition). 


Figure 14-1. Cell division and fertilization. 

14-6. FERTILIZATION 

To produce a new individual, the male gamete (spermatozoon) must join with the female gamete (ovum). This joining of the gametes is called fertilization. The gametes join to form a zygote. The zygote is a single cell which is the beginning of a new human being. The zygote has two sets of chromosomes (46), the appropriate number for the human species. Thus, in the process of fertilization, the human genetic makeup is reconstituted. 
The existence of separate male and female sexes provides an important advantage. Each individual is the product of a new combination of human genetic material. Thus, there is always the potential for improvement in the human species. 
14-7. TERMINOLOGY 

Genotype/Phenotype. The genotype is the actual genetic makeup of an individual. The phenotype is the physical and functional makeup of an individual as determined both by the genotype and the environment. 
Dominant/Recessive. Consider a gene in one set of chromo-somes and the corresponding gene in the other set. If one of the genes alone can produce a characteristic of the phenotype, the gene is said to be dominant. If both genes must be the same to produce a characteristic of the phenotype, then the genes are recessive. In a situation where one of the pair is dominant and the other is recessive, the dominant gene determines the ultimate characteristic. 
Homozygous/Heterozygous. Again, consider a gene in one set of chromosomes and the corresponding gene in the other set. If the two genes are the same, we say that the individual is homozygous for that trait. If the two genes are different, we say that the individual is heterozygous for that trait. 
Fraternal/Identical. In multiple births, two or more of the newborn may or may not resemble each other closely. They may resemble each other in sex (gender) and other physical and functional traits. 
(1) If two of the individuals are different, they are called fraternal twins. 
(2) If they closely resemble each other, they are called identical twins. Identical twins are believed to originate in a common zygote, which separates into two entities at a very early stage. Thus, identical twins have the same genetic makeup. However, one is often right-oriented and the other left-oriented. 
14-8. SOME SIMPLE GENETIC COMBINATIONS (CROSSINGS) 

The Monohybrid Crossing (Figure 14-2). Again, consider a gene in one set of chromosomes and the corresponding gene in the other set. This involves two genes of a single inherited element. Assume that each parent has one dominant gene (A) and one recessive gene (a), a heterozygous condition (Aa). Thus, 50% of the gametes from each parent will carry the dominant gene (A), and 50% of the gametes will carry the recessive gene (a). The potential crossings of the genes are AA, Aa, Aa, and aa. 


Figure 14-2. A monohybrid crossing. 

(1) If we perform many identical monohybrid crossings of this type, one-quarter of the offspring will be homozygous for the dominant gene (AA). One-half will be heterozygous (Aa), having one dominant and one recessive gene. The remaining quarter will be homozygous for the recessive gene (aa). 
(2) Three-quarters of the offspring (AA or Aa) will have the phenotype trait produced by the dominant gene (A). One-quarter (aa) will show the phenotype trait produced by the recessive gene. 
(3) As we have seen, the heterozygous organisms (Aa) make up 50% of the offspring. These are often called carriers. Although their phenotype does not show the recessive trait, they can still transmit that trait to their offspring. 
The Dihybrid Crossing (Figure 14-3). Now, consider two genes in one set of chromosomes and the corresponding pair of genes in the other set. Assume that each parent is heterozygous for both genes (AaBb), where A and B are dominant and a and b are recessive. The potential gametes from each parent will then have gene pairs AB, Ab, aB, or ab. 


Figure 14-3. A dihybrid crossing. 

(1) If we perform many identical dihybrid crossings of this type, 14 out of 16 (7 out of 8) will have genotypes including both dominant and recessive genes. One-fourth will be AaBb. AaBB, AABb, Aabb, and aaBb will each account for one-eighth of the total offspring. AABB, AAbb, aaBB, and aabb will each account for one-sixteenth of the total offspring. Thus, one-fourth (4 out of 16) are homozygous. 
(2) This example helps to illustrate the consequences of large numbers of gene pairs. Since there are many, many pairs of genes in the 46 chromosomes of humans, there will be a huge number of different offspring that are possible. Thus, except in the case of identical twins, the occurrence of genetically identical persons is virtually impossible. 
NOTE: The proportions of genotypes given for these crossings are statistical estimates based on many repetitions. For any one offspring, any one of the possibilities can occur.

14-9. MODIFYING CONDITIONS

Often, there is no clear-cut dominance or recessiveness within a pair of genes. Also, most human traits are influenced by more than one pair of genes. 

Incomplete Dominance. In incomplete dominance, the heterozygous condition (Aa) produces a phenotype partially resembling both the homozygous dominant condition (AA) and the homozygous recessive condition (aa). An example is Wol man's disease, a homozygous recessive condition leading to the accumulation of lipids in the body. Persons who are heterozygous for this trait tend to have a high level of cholesterol in their serum. 
Complementary Inheritance. In complementary inheritance, two independent pairs of genes affect a trait. Both must be present for a trait to occur. 
Multifactorial Inheritance. Most human characteristics are affected by a number of gene pairs. 
14-10. CLINICAL IMPLICATIONS

Genes can be affected and changed by a number of circumstances. Some changes may be beneficial. Other may be harmful. In either case, the effects will be transmitted to one's offspring. 

A gene may be lost, for example, by a gamete. The resulting off-spring may then not have a certain trait. For example, some individuals are unable to produce a specific enzyme because they do not have the appropriate gene. A metabolic process using that enzyme may be impossible for that individual. 
Some individuals may have an excessive number of genes. Examples are individuals with an extra X or Y chromosome. This can substantially affect both anatomy and personality. 
Genetic charts and genetic counseling are sometimes used to advise prospective parents of genetic problems they may expect with their offspring. 
Technical advances in the biological sciences have made genetic engineering possible. Thus, we see the rise of an industry devoted to altering the genetic makeup of microorganisms for the purpose of producing certain chemicals. The chief value of many of these chemicals will be to correct deficiencies in humans, such as insulin for diabetes. (In cloning, individual cells are cultured to produce numerous organisms, all with the same genotype.) 


Figure 14-4. A sex-linked monohybrid crossing.
 
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1402.jpg]]

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1403.jpg]]

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1404.jpg]]
http://www.innerbody.com/htm/body.html
 Unit 7 The Human Respiratory System and Breathing

Lessons (select one)
 Topics
 
 Lesson 1  Introduction  Purpose of Respiration and Breathing - Definitions - Physical Principles - General Anatomy and Construction of the Human Trunk 
 Lesson 2   Introduction To Human Breathing  Definition - Use of Pressure Gradients - Types of Human Breathing - Lung Capacities - Breathing Cycles 
 Lesson 3   Costal ('Thoracic') Breathing  Definition - Anatomy of the Human Rib Cage - Costal Inhalation - Costal Exhalation 
 Lesson 4   Diaphragmatic ('Abdominal') Breathing Physical Characteristics of the Abdominopelvic Cavity - Thoracic Diaphragm - Diaphragmatic Inhalation - Diaphragmatic Exhalation 
 Lesson 5   Introduction To the Human Respiratory System  General - Divisions 
 Lesson 6   The Supralaryngeal Structures  General Functions - Nose - Nasal Chambers - Nasopharynx - Pharynx and Function of Soft Palate 
 Lesson 7   Larynx  Introduction - Larynx As A Part of the Hyoid Complex - General Functions of the Larynx - Control of Volume of Air - Production of Human Speech 
 Lesson 8  The 'Respiratory Tree' and Pulmonary Alveoli  Introduction - Trachea - Bronchi - 'Dead Air' - Pulmonary Alveoli 
 Lesson 9   Lungs and Pleural Cavities  Introduction - Lung Structure - Pleural Cavities 
 Lesson 10   The Pulmonary NAVL Nervous Control of Breathing - Functional Blood Supply 
 Lesson 11   Exchange and Transportation of Gases: Artificial Breathing/Resuscitation  Exchange and Transportation of Gases - Artificial Breathing/Resuscitation 


 

 

 

 

 
 Learning Objectives

After completing this lesson, you should be able to: 

Match characteristics and processes of breathing and respiration with their descriptions. 
Given a list of sentences about respiration or breathing, select the false statement. 
Complete incomplete sentences about breathing or respiration. 

 

 

 
 
 Lesson 2
INGESTION AND INITIAL PROCESSING OF FOODS

6-4. INGESTION

a.      Hunger. When an individual needs foods, he experiences a sensation known as hunger. The hypothalamus area of the brain controls the degree of hunger or satiation (feeling of being well fed). To do this, the hypothalamus receives various types of information from throughout the body.

b.      Food Selection. When food is presented, an individual goes through a process of food selection. He or she has a greater appetite for some foods than others. This process is related both to previous learning and to current, internal chemical requirements.

c.      Biting. Together, the upper and lower incisors (anterior teeth) create two cutting surfaces like a pair of scissors. As food items are placed in the opening of the oral cavity, bite-size chunks of food are cut off. These chunks are usually just the right size for the mouth to handle.

6-5. TWO KEY FACTS ABOUT DIGESTION

In general terms, there are two key facts to understand about digestion: 

a.      First, digestion is a chemical process. Through a process called hydrolysis, food is broken down into its constituent parts. 
b.     Second, this chemical process takes place only at wet surfaces of the food. 
6-6. MASTICATION

During the process known as mastication (chewing), the food particles are gradually broken down into smaller and smaller pieces. At the same time, the total surface area of the food increases greatly. 

a.      This grinding and crushing of the food particles are accomplished by the posterior teeth, the premolar and molar teeth. For this purpose, these teeth have broad, opposing surfaces. 
b.      Together, the tongue and cheeks act to keep the food particles between the surfaces of the grinding teeth. This is accomplished as the lower jaw moves up and down. 
6-7. SALIVA 

a.      Secreting fluids into the oral cavity are such glandular structures as the salivary glands and the buccal glands. (The buccal glands are serous and mucous glands on the inner surfaces of the cheeks.) These fluids are collectively known as the saliva. 
b.      Saliva serves to wet the surface areas of the food particles produced by mastication. In addition, saliva also dissolves some of the molecules of the food items. 
c.      Taste buds sample these dissolved molecules and test the quality of the food being eaten. Taste buds are located on the tongue and the back of the oral cavity. 
d.      Another component of the saliva is mucus. The mucus tends to hold the food particles together as a bolus. Since the mucus also makes this bolus somewhat slippery, the bolus can slide readily through the initial portion of the digestive tract.  
 Lesson 3
INTEGUMENTARY DERIVATIVES

3-11. INTRODUCTION

A number of structures are derived from the layers of the integument proper. These structures are referred to as the integumentary derivatives or "appendages."

3-12. HAIRS

More or less covering the body are derivatives called hairs. The hairs of the body vary in construction from area to area. An individual's genes determine the specific construction, growth, and pattern of hairs for that individual. Sex hormones more or less control the distribution of hairs (sexual dimorphism). Also, in different cultures of human beings, different patterns of hair growth have arisen because of cultural selection.

3-13. NAILS

Another integumentary derivative is the nails. A nail covers the dorsal aspect of the end of each digit (fingers and toes).

3-14. GLANDS

The various glands are another kind of integumentary derivative.

Sweat Glands. There are at least two types of sweat (sudoriferous) glands:

The general type throughout the body. This type produces a sensible and insensible perspiration. (See paragraph 2-7c(1).) 
A second type found in special areas. This type is found especially in the palms of the hands. Such sweat glands respond to emotional stresses to produce the "clammy" hands of the frightened individual. 
Sebaceous Glands. Oil-producing (sebaceous) glands are usually found in relationship to the hair follicles. The oily product of these glands keeps the following structures flexible:

The outer layers of the skin. 
The shafts of the hairs. 
True Scent Glands. A third type of gland associated with the integument is the true scent gland. At least in older days, the product of these glands was supposed to be attractive to the opposite sex. (Here, we are not referring to the body odor known as BO. BO is a metabolic by-product produced by microorganisms located on the skin. These microorganisms act upon residue from perspiration, left after the water has evaporated.)
 
 Lesson 5
INTRAUTERINE DEVELOPMENT

9-19. GENERAL

The site of fertilization (when it occurs) is usually in the uterine tube. Initial development of the embryo also takes place in the uterine tube. However, most development is intrauterine (within the uterus). 

Embryo. During the first 8 weeks of development, the developing individual is called an embryo. The processes by which the embryo develops are studied in embryology. 
Fetus. During the remainder of the intrauterine period, the developing individual is known as the fetus. During this latter period, the details of structure and function develop. 
9-20. SUPPORT OF THE EMBRYO AND FETUS

In paragraph 9-1 5b(2), we discussed the amniotic sac, umbilical cord, and placenta. During intrauterine development, the embryo/ fetus is within the amniotic sac. Floating free in the amniotic fluid, it is connected to the placenta by the umbilical cord. The placenta is the specific area of exchange between the maternal blood and the fetal blood. By this exchange, the fetus gets rid of waste materials and acquires food, oxygen, and other needed substances from the mother.
 
 Lesson 2
INTRODUCTION TO HUMAN BREATHING

7-5. DEFINITION

Breathing is basically the process of moving air into and out of the lungs. 

7-6. USE OF PRESSURE GRADIENTS

Breathing is accomplished by manipulating the pressure gradient between the surrounding atmosphere and the thoracic cavity. For all practical purposes, the pressure of the surrounding atmosphere can be considered a constant. Thus, the desired pressure gradients are achieved by changing the pressure within the thoracic cavity. The pressure in the thoracic cavity alternates so that it is less and then greater than the pressure of the surrounding atmosphere.

7-7. TYPES OF HUMAN BREATHING

The two types of human breathing are costal and diaphragmatic. They may be used individually and independently, or they may be used in combination.

7-8. LUNG CAPACITIES 

Total Lung Capacity. From the instant of the "first breath," the lungs have a certain total volume called the total lung capacity. This is the entire volume of air in the lungs after one inhales as much as one can. Total lung capacity equals the sum of the residual volume and the vital capacity. 
Residual Volume. After the "first breath," the lungs are never completely emptied. Thus, there is a certain portion of air that is always present in the lungs. After one exhales as much air as possible, the portion remaining in the lungs is called the residual volume. In actuality, this is not "dead air," because air circulation continually refreshes the air of the residual portion. 
Vital Capacity. The vital capacity of the lung is the total amount of air that can be exchanged during total filling and emptying of the lung. For example, if one inhales as much air as one can and then exhales as much as possible, the volume exhaled would be the vital capacity. 
7-9. BREATHING CYCLES

A breathing (respiratory) cycle is a sequence in which the lungs are filled and emptied to produce an exchange of the air in the lungs. The cycle includes an inhalation of air (filling of the lung with air), then a rapid exhalation (emptying), and then a short rest period. See Figure 7-2 for a representation of the "filling" of the lungs.

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0702.jpg]]

Figure 7-2. "Filling" of the lungs. 

Volume Exchanges During Breathing. The amount of air exchanged in a given period depends upon the rate and depth (volume) of breathing. Rate and depth are adjusted according to physiological demand. The rate of respiration is the number of breathing cycles per minute. 
Some Types of Breathing Cycles. 
(1)  Quiet ("tidal") breathing. As one takes part in ordinary, low-level activity, the breathing cycles are of the quiet type. This type involves only a minimal exchange of air. 
(2)  Complementary cycle. Over a period of time, quiet breathing may not totally satisfy the oxygen requirements of the body. Thus, we can observe a breathing cycle with a slightly greater volume exchange called the complementary cycle. It provides a little extra oxygen to make up the difference. 
(3)  Forced breathing. In forced breathing, the volumes of air exchanged are much greater than in quiet breathing. The actual volume exchanged depends upon the oxygen demand. 
(4) Holding of breath. One can inhale a volume of air and hold it for a period. If one makes an exhalation effort but still holds the air inside the lungs, it is called Valsalva's maneuver (forced expiration against a closed glottis). 
(5)  Cough. If one suddenly releases the air, terminating Valsalva's maneuver, the result is a cough. If the musculature of a patient's abdominal wall is paralyzed, the patient cannot execute the Valsalva's maneuver and cannot produce a cough. 
(6)        Speech. During speech or vocalization, the breathing cycles overlap. That is, the subsequent cycle begins before the previous one is ended. The purpose of this is to maintain a continuous outflow of air.  
 Lesson 5
INTRODUCTION TO THE HUMAN RESPIRATORY SYSTEM

7-18. GENERAL

The human respiratory system consists of a series of organs that form a passageway for the air flowing to and from the alveoli of the lungs. The lungs themselves are discrete organs of the body containing the alveoli and are located in individual serous cavities.

7-19. DIVISIONS

The air passageway can be conveniently divided into three groups of structures. The larynx is the central portion. The other organs are grouped as supra laryngeal or infra-laryngeal.
 
 Lesson 6
INVESTING DEEP FASCIA

3-23. INTRODUCTION

The innermost of these three concentric layers is the investing deep fascia. The investing deep fascia is essentially a membrane of dense FCT completely surrounding the body. It overlies all of the remaining structures of the body.

3-24. VARIATIONS IN THICKNESS

The investing deep fascia varies in thickness in various parts of the body. This membrane is generally thicker the further inferior we go. In many areas, it is thick enough to be specifically named. For example, the investing deep fascia of the lower member is called the fascia lata.

The majority of the tissues of the body are made up primarily of water. Moreover, the interstitial spaces are filled with water. Therefore, the body within the investing deep fascia can be thought of as a hydrostatic column. As such, hydrostatic pressures become greater as one goes inferiorly in the body. Accordingly, the fascia becomes thicker to withstand the increasing pressures.

3-25. INTERMUSCULAR SEPTA

In the limbs of the upper and lower members, dense FCT membranes extend from the underside of the investing deep fascia to the bones. The membranes are known as the intermuscular septa. They divide the space within the investing deep fascia into discrete muscular compartments.

Each muscular compartment is a hydrostatic chamber. In a normal healthy human being, each compartment is full. Therefore, as arterial blood flows into a compartment, hydrostatic pressures are created which assist the flow of blood in the venous vessels back to the heart.
 
An immune system is a collection of mechanisms within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy cells and tissues in order to function properly. Detection is complicated as pathogens adapt and evolve new ways to successfully infect the host organism.

To survive this challenge, several mechanisms have evolved that recognize and neutralize pathogens. Even simple unicellular organisms such as bacteria possess enzyme systems that protect against viral infections. Other basic immune mechanisms evolved in ancient eukaryotes and remain in their modern descendants, such as plants, fish, reptiles, and insects. These mechanisms include antimicrobial peptides called defensins, phagocytosis, and the complement system. More sophisticated mechanisms, however, developed relatively recently, with the evolution of vertebrates.[1] The immune systems of vertebrates such as humans consist of many types of proteins, cells, organs, and tissues, which interact in an elaborate and dynamic network. As part of this more complex immune response, the vertebrate system adapts over time to recognize particular pathogens more efficiently. The adaptation process creates immunological memories and allows even more effective protection during future encounters with these pathogens. This process of acquired immunity is the basis of vaccination.

Disorders in the immune system can cause disease. Immunodeficiency diseases occur when the immune system is less active than normal, resulting in recurring and life-threatening infections. Immunodeficiency can either be the result of a genetic disease, such as severe combined immunodeficiency, or be produced by pharmaceuticals or an infection, such as the acquired immune deficiency syndrome (AIDS) that is caused by the retrovirus HIV. In contrast, autoimmune diseases result from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Common autoimmune diseases include rheumatoid arthritis, diabetes mellitus type 1 and lupus erythematosus. These critical roles of immunology in health and disease are areas of intense scientific study.
Innate Immunity

The innate immunity system is what we are born with and it is nonspecific; all antigens are attacked pretty much equally. It is genetically based and we pass it on to our offspring.

Surface Barriers or Mucosal Immunity

The first and, arguably, most important barrier is the skin. The skin cannot be penetrated by most organisms unless it already has an opening, such as a nick, scratch, or cut. 
Mechanically, pathogens are expelled from the lungs by ciliary action as the tiny hairs move in an upward motion; coughing and sneezing abruptly eject both living and nonliving things from the respiratory system; the flushing action of tears, saliva, and urine also force out pathogens, as does the sloughing off of skin. 
Sticky mucus in respiratory and gastrointestinal tracts traps many microorganisms. 
Acid pH (< 7.0) of skin secretions inhibits bacterial growth. Hair follicles secrete sebum that contains lactic acid and fatty acids both of which inhibit the growth of some pathogenic bacteria and fungi. Areas of the skin not covered with hair, such as the palms and soles of the feet, are most susceptible to fungal infections. Think athlete's foot. 
Saliva, tears, nasal secretions, and perspiration contain lysozyme, an enzyme that destroys Gram positive bacterial cell walls causing cell lysis. Vaginal secretions are also slightly acidic (after the onset of menses). Spermine and zinc in semen destroy some pathogens. Lactoperoxidase is a powerful enzyme found in mother's milk. 
The stomach is a formidable obstacle insofar as its mucosa secrete hydrochloric acid (0.9 < pH < 3.0, very acidic) and protein-digesting enzymes that kill many pathogens. The stomach can even destroy drugs and other chemicals. 
 
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Lesson 1-1
Introduction to Basic Human Physiology

After completing this lesson, you should be able to: 

Define physiology. 
Describe the levels of function and the relationship between structure and function in the human body. 
Identify the effects of fundamental laws, concepts, and forces of the Universe. 
Identify processes which distinguish living from nonliving objects. 
Match three somatotypes with their descriptions. 
Identify general body functions and their descriptions. 
Identify fundamental processes for providing energy to human beings. 

 

1-1. DEFINITION

Physiology is the study of the functions of the body at the cellular level. 

 

1-2. LEVELS OF FUNCTION

Function in the human body occurs at three general levels:

a.      Molecular. The basic functional entity is the molecule. The structure and interaction of the molecules of the body is the subject of the science of biochemistry.

b.      Cellular. The individual cell is the basis of the structure and function of the human body. The individual human body consists of great numbers of these cells working together as a total organism. Groups of like cells performing a common function are called tissues. Different tissues collected together form individual organs. Groups of organs performing an overall function are called organ systems, for example, the digestive system, the respiratory system, etc. When these systems are together in a single individual, we refer to that individual as an organism. The cellular level of function is the primary subject matter of physiology.

c.      Regional. Here, individual parts of the human body (made up of specific organs) perform activities as a unit. For example, the hand serves as a grasping, tool-holding apparatus. The study of this level of function is called functional anatomy.

 

1-3. INTERRELATIONSHIPS

There is an inseparable relationship between structure and function in the human body. Every structure is designed to perform a particular function or functions. Likewise, every function has structures designed to perform it.

 

1-4. LAWS OF NATURE

The Universe has a fundamental order. The Universe is governed by discrete and precise laws of nature. These laws are universal, unchangeable, and omnipresent. The human organism is ultimately controlled by these laws. The organic body of the human being is essentially operated by the laws of physics and chemistry.

a. Gravitational Force and Mass.

(1) Gravitational force. As you stand upon the surface of the Earth, your body and its parts experience the force called gravity. The measure of this force is called weight. Gravity is one type of gravitational force, a force which attracts all particles and bodies to each other. Gravity acts upon your body during every instant of your life.

(2) Mass. If you were standing on the surface of the Moon, you would weigh 1/6 of your weight on Earth, but your mass would remain the same. Mass is an intrinsic property of a particle or object that determines its response to a given force. In a given location, the weight of an object depends upon its mass.

b.      Space and Time. Each individual occupies a certain amount of space. We exist over a span of time. During the passage of time, we change--from an infant, to a child, to an adult, to an adult of advanced age.

c.      Physical States of Matter. The matter around and in us exists in several states. These various states generally reflect the closeness of the molecules that make up the matter.

(1)     Solid. The most compact organization is the solid, which retains its specific form and shape.

(2)     Liquid. Liquids tend to flow but still stay together.

(3)     Gas. Gases also flow but are widely spread and will readily dissipate in many directions.

d.      Pressure Gradients. Substances that flow (gases and liquids) flow in very specific directions. They flow from an area of higher pressure or concentration to an area of lower pressure or concentration as long as the two areas are freely interconnected. The difference in pressures of two interconnected areas is called a pressure gradient. When plotted on graph paper, it is in the form of a slope. The greater the difference, the steeper is the slope and the faster the material flows.

 

1-5. MECHANICS/BIOMECHANICS

Machines are devices that do work. The different kinds of machines and their modes of action are the study of applied mechanics. The human body, as already stated, conforms in its structural organization to the laws of physics. The body uses several different kinds of machines, such as levers, pulleys, and valves, in its operation. We refer to these operations as biomechanics.

 

1-6. LIFE PROCESSES

The planet upon which we live is composed of inanimate (nonliving) materials such as minerals, water, etc. Living organisms reside upon or in this mass of nonliving material. You can distinguish living from nonliving material by the fact that living material carries on a series of functions known as the life processes. A living thing takes in substances, grows, moves, is irritable, and reproduces. Often, it is difficult to distinguish between living and nonliving materials. But in the ultimate analysis only living materials perform all of these functions.

 

1-7. VARIATIONS AMONG HUMAN ORGANISMS

The human organism is known scientifically as Homo sapiens, meaning the intelligent human being. There is a more or less common form for human beings. This common form includes one head, two upper members, two lower members, etc., but there are no two individuals exactly alike in detail. (This even includes identical twins. One tends to be left-oriented and the other right-oriented.) As a result, there is a tremendous variation among humans which has been further complicated by selection and propagation of specific traits by humans themselves.

 

1-8. SOMATOTYPES

Given the variations among human organisms, various methods of categorization have been established to achieve some common order. The method we will use is referred to as somatotyping. See Figure 1-1.

  

Figure 1-1. Human somatotypes.

a. In this method, human beings are categorized into three different groups:

(1)        Ectomorphs, who tend to be thin-bodied individuals.

(2)        Endomorphs, who tend to be broad-bodied individuals.

(3)        Mesomorphs, who have a body form between the other two.

b. It has been demonstrated that there are significant differences among human beings in these categories. These differences exist not only in body form but also in internal anatomy of structures and susceptibility to diseases.

 

1-9. GENERAL BODY FUNCTIONS

The living human being performs many functions as a part of daily life.

a.      Nutrition. The body takes in materials for energy, growth, and repair. Since the body cannot produce its own energy, it must continually take in foods to supply that energy to carry on the life processes. This food also provides materials for growth and repair of the cells and tissues.

b.      Motion and Locomotion. Being an erect, standing organism, the body requires special supporting structures. At the same time, it needs a mechanical arrangement to allow the parts to move (motion) and to move from place to place (locomotion).

c.      Reproduction. For the species to continue, there must be reproduction, the formation of new human beings belonging to subsequent generations.

d.      Control. All of this activity is controlled by three major systems of the body--heredity/environment, hormones, and the nervous system. Hormones provide a chemical control system. The nervous system works much like circuitry in a computer. In the final analysis, however, all of the structures and functions of the body are determined by special units called genes, the study of which is genetics and the transmission of which is heredity. Heredity determines the potential range of an organism's characteristics. The environment determines which potential characteristics are developed and to what degree.

 

1-10. ENERGY

As we have previously mentioned, energy is required to carry on the life processes of each individual human being.

a. One of the laws of nature is conservation of energy. This means that energy cannot be created or destroyed but only transformed. For example, electricity can be

transformed into heat. The human body cannot produce energy on its own and must, therefore, continuously take in a fresh supply of energy.

b.      Except for a few special situations, all of the energy for living matter on Earth is received from the Sun through solar radiation. Green plants trap and bind this solar energy in molecules of glucose by the process of photosynthesis.

c.      Humans take this glucose into their bodies directly by eating green plants or indirectly by eating the flesh of plant-eating animals. The human body releases the trapped energy from glucose by a process known as metabolic oxidation.

d.      The released energy is used to form the compound ATP (adenosine triphosphate) from ADP (adenosine diphosphate). ATP is like a charged battery; the "discharged battery" is called ADP. Molecules of ATP are present in all of the living cells of the body. Within each cell, molecules of ATP are "discharged" to release a large quantity of energy to drive the various life processes. Through further metabolic oxidation, the resulting ADP molecules are "recharged" to form ATP molecules once again.
[[Jim Frank Story]]

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Chapter 22: The Lymphatic System and Immunity  
   
 100 Keys 
   
 Cell-mediated immunity involves close physical contact between activated Tc cells and foreign, abnormal, or infected cells. T cell activation usually involves (1) antigen presentation by a phagocytic cell and (2) costimulation by cytokines released by active phagocytes. Tc cells may destroy target cells through the local release of cytokines, lymphotoxins, or perforin. 

Antibody-mediated immunity involves the production of specific antibodies by plasma cells derived from activated B cells. B cell activation usually involves (1) antigen recognition, through binding to surface antibodies, and (2) costimulation by a TH cell. The antibodies produced by active plasma cells bind to the target antigen and either inhibit its activity, destroy it, remove it from solution, or promote its phagocytosis by other defense cells. 

Immunization produces a primary response to a specific antigen under controlled conditions. If the same antigen is encountered at a later date, it triggers a powerful secondary response that is usually sufficient to prevent infection and disease. 

Viruses replicate inside cells, whereas bacteria may live independently. Antibodies (and administered antibiotics) work outside cells, so they are primarily effective against bacteria rather than viruses. (That's why antibiotics can't fight the common cold or flu.) T cells, NK cells, and interferons are the primary defenses against viral infection. 
 




Copyright © 1995-2008 by Benjamin Cummings A division of Pearson Education Legal Disclaimer 


 
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Citric acid cycle
From Wikipedia, the free encyclopedia
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Overview of the citric acid cycleThe citric acid cycle [also known as the tricarboxylic acid (TCA) cycle, the Krebs cycle, or Szent-Györgyi-Krebs cycle (after Hans Adolf Krebs and Albert Szent-Györgyi who first determined the chemical intermediates and reaction sequence of the cycle)] is a series of enzyme-catalysed chemical reactions of central importance in all living cells that use oxygen as part of cellular respiration. In aerobic organisms, the citric acid cycle is part of a metabolic pathway involved in the chemical conversion of carbohydrates, fats and proteins into carbon dioxide and water to generate a form of usable energy. It is the third of four metabolic pathways that are involved in carbohydrate catabolism and ATP production, the other three being glycolysis and pyruvate oxidation before it, and electron transport chain after it.

The citric acid cycle also provides precursors for many compounds such as certain amino acids, and some of its reactions are therefore important even in cells performing fermentation.

Contents [hide]
1 Overview 
2 A simplified view of the process 
3 Products 
4 Regulation 
5 Major metabolic pathways converging on the TCA cycle 
6 See also 
7 References 
8 External links 
 


[edit] Overview
Two carbons are oxidized to CO2, and the energy from these reactions is stored in GTP, NADH and FADH2. NADH and FADH2 are coenzymes (molecules that enable or enhance enzymes) that store energy and are utilized in oxidative phosphorylation.

Step Substrate Enzyme Reaction type Reactants/
Coenzymes Products/
Coenzymes Comment 
1 Oxaloacetate  Citrate synthase  Condensation Acetyl CoA +
H2O CoA-SH  
2 Citrate  Aconitase  Dehydration  H2O  
3 cis-Aconitate  Aconitase  Hydration H2O   
4 Isocitrate  Isocitrate dehydrogenase  Oxidation NAD+ NADH + H+
  
5 Oxalosuccinate  Isocitrate dehydrogenase  Decarboxylation H+ CO2  
6 α-Ketoglutarate  α-Ketoglutarate dehydrogenase  Oxidative
decarboxylation NAD+ +
CoA-SH NADH + H+
+ CO2  
7 Succinyl-CoA  Succinyl-CoA synthetase  substrate level phosphorylation GDP + Pi GTP +
CoA-SH or ADP->ATP 
8 Succinate  Succinate dehydrogenase  Oxidation FAD FADH2  
9 Fumarate  Fumarase  Addition (H2O) H2O   
10 L-Malate  Malate dehydrogenase  Oxidation NAD+ NADH + H+  


[edit] A simplified view of the process
The citric acid cycle begins with Acetyl-CoA transferring its two-carbon acetyl group to the four-carbon acceptor compound, oxaloacetate, forming citrate, a six-carbon compound. 
The citrate then goes through a series of chemical transformations, losing first one, then a second carboxyl group as CO2. 
Most of the energy made available by the oxidative steps of the cycle is transferred as energy-rich electrons to NAD+, forming NADH. For each acetyl group that enters the citric acid cycle, three molecules of NADH are produced. 
Electrons are also transferred to the electron acceptor FAD, forming FADH2. 
At the end of each cycle, the four-carbon oxaloacetate has been regenerated, and the cycle continues. 

[edit] Products
Products of the first turn of the cycle are: one GTP, three NADH, one FADH2, and two CO2

Because two acetyl-CoA molecules are produced from each glucose molecule, two cycles are required per glucose molecule. Therefore, at the end of all cycles, the products are: two GTP, six NADH, two FADH2, and four CO2

Description Reactants Products 
The sum of all reactions in the citric acid cycle is: Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi + 2 H2O → CoA-SH + 3 NADH + 3 H+ + FADH2 + GTP + 2 CO2 
Combining the reactions occurring during the pyruvate oxydation with those occurring during the citric acid cycle, we get the following overall pyruvate oxidation reaction before the respiratory chain: Pyruvic acid + 4 NAD+ + FAD + GDP + Pi + 2 H2O → 4 NADH + 4 H+ + FADH2 + GTP + 3 CO2 
Combining the above reaction with the ones occurring in the course of glycolysis, we get the following overall glucose oxidation reaction before the respiratory chain: Glucose + 10 NAD+ + 2 FAD + 2 ADP + 2 GDP + 4 Pi + 2 H2O → 10 NADH + 10 H+ + 2 FADH2 + 2 ATP + 2 GTP + 6 CO2 

(the above reactions are equilibrated if Pi represents the H2PO4- ion, ADP and GDP the ADP2- and GDP2- ions respectively, ATP and GTP the ATP3- and GTP3- ions respectively).

Considering the future conversion of GTP to ATP and the maximum 32 ATP produced by the 10 NADH and the 2 FADH2 (see the theoretical yields for cellular respiration), we see that each glucose molecule is able to produce a maximum of 32 ATP.


[edit] Regulation
Although pyruvate dehydrogenase is not technically a part of the citric acid cycle, its regulation is included here.

Many of the enzymes in the TCA cycle are regulated by negative feedback from ATP when the energy charge of the cell is high. Such enzymes include the pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase. These enzymes, which regulate the first three steps of the TCA cycle, are inhibited by high concentrations of ATP. This regulation ensures that the TCA cycle will not oxidise excessive amounts of pyruvate and acetyl-CoA when ATP in the cell is plentiful. This type of negative regulation by ATP is by an allosteric mechanism.

Several enzymes are also negatively regulated when the level of reducing equivalents in a cell are high (high ratio of NADH/NAD+). This mechanism for regulation is due to substrate inhibition by NADH of the enzymes that use NAD+ as a substrate. This includes pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, and malate dehydrogenase.

Calcium is used as a regulator. It activates pyruvate dehydrogenase, isocitrate dehydrogenase and oxoglutarate dehydrogenase.[1] This increases the reaction rate of many of the steps in the cycle, and therefore increases flux throughout the pathway.

Citrate is used for feedback inhibition, as it inhibits phosphofructokinase, an enzyme involved in glycolysis that makes fructose 1,6-bisphosphate), a precursor of pyruvate. This prevents a constant high rate of flux when there is an accumulation of citrate and a decrease in substrate for the enzyme.

Recent work has demonstrated an important link between intermediates of the citric acid cycle and the regulation of hypoxia inducible factors (HIF). HIF plays a role in the regulation of oxygen haemostasis and is a transcription factor which targets angiogenesis, vascular remodelling, glucose ulitisation, iron transport and apoptosis. HIF is synthesized consititutively and hydropxylation of at least one of two critical proline residues mediates their interation with the von Hippel Lindau E4 ubiquitin ligase complex which targets them for rapid degradation. This reaction is calalysed by prolyl 4-hydroxylases. Fumarate and succinate have been identified as potent inhibitors of prolyl hydroxylases thus leading to the stabilisation of HIF.[2]


[edit] Major metabolic pathways converging on the TCA cycle
Most of the body's catabolic pathways converge on the TCA cycle, as the diagram shows. Reactions that form intermediates of the TCA cycle in order to replenish them (especially during the scarcity of the intermediates) are called anaplerotic reactions.

The citric acid cycle is the third step in carbohydrate catabolism (the breakdown of sugars). Glycolysis breaks glucose (a six-carbon-molecule) down into pyruvate (a three-carbon molecule). In eukaryotes, pyruvate moves into the mitochondria. It is converted into acetyl-CoA by decarboxylation and enters the citric acid cycle.

In protein catabolism, proteins are broken down by protease enzymes into their constituent amino acids. These amino acids are brought into the cells and can be a source of energy by being funnelled into the citric acid cycle.

In fat catabolism, triglycerides are hydrolyzed to break them into fatty acids and glycerol. In the liver the glycerol can be converted into glucose via dihydroxyacetone phosphate and glyceraldehyde-3-phosphate by way of gluconeogenesis. In many tissues, especially heart tissue, fatty acids are broken down through a process known as beta oxidation which results in acetyl-CoA which can be used in the citric acid cycle. Sometimes beta oxidation can yield propionyl CoA which can result in further glucose production by gluconeogenesis in the liver.

The citric acid cycle is always followed by oxidative phosphorylation. This process extracts the energy (as electrons) from NADH and FADH2, oxidizing them to NAD+ and FAD, respectively, so that the cycle can continue. The citric acid cycle itself does not use oxygen, but oxidative phosphorylation does.

The total energy gained from the complete breakdown of one molecule of glucose by glycolysis, the citric acid cycle and oxidative phosphorylation equals about 36 ATP molecules. The citric acid cycle is called an amphibolic pathway because it participates in both catabolism and anabolism.


[edit] See also
Calvin cycle 
Oxidative decarboxylation 
Citric acid 
Glycolysis 
Pyruvate decarboxylation 
Oxidative phosphorylation 
Reverse (Reductive) Krebs cycle 
Hans Adolf Krebs 

[edit] References
^ Denton RM; Randle PJ, Bridges BJ, Cooper RH, Kerbey AL, Pask HT, Severson DL, Stansbie D, Whitehouse S. (Oct 1975). "Regulation of mammalian pyruvate dehydrogenase". Mol Cell Biochem 9 (1): 27-53.  
^ Koivunen P, Hirsilä M, Remes AM, Hassinen IE, Kivirikko KI, Myllyharju J (2007). "Inhibition of hypoxia-inducible factor (HIF) hydroxylases by citric acid cycle intermediates: possible links between cell metabolism and stabilization of HIF". J. Biol. Chem. 282 (7): 4524–32. PMID 17182618.  
Neil A. Campbell; Jane B. Reece (Dec 2005). Biology, 7th ed., Benjamin Cummings. ISBN 978-0805371468.  
Solomon, E.P.; Berg, L.R., Martin, D.W. (Mar 2005). Biology. Brooks Cole. ISBN 978-0534495480.  

[edit] External links
An animation of the citric acid cycle at Smith College 
A video of members of The Ohio State Marching Band enacting the Krebs cycle at YouTube 
Notes on citric acid cycle at rahulgladwin.com 
A more detailed tutorial animation at johnkyrk.com 
A citric-acid cycle self quiz flash applet at University of Pittsburgh 
The chemical logic behind the citric acid cycle at ufp.pt 
[show]v • d • eMajor subtopics of biology 
Anatomy - Astrobiology - Biochemistry - Bioinformatics - Botany - Cell biology - Ecology - Developmental biology - Evolutionary biology - Genetics - Genomics - Marine biology - Human biology - Microbiology - Molecular biology - Origin of life - Paleontology - Parasitology - Pathology - Physiology - Taxonomy - Zoology 
[show]v • d • eCellular Respiration 
Aerobic Respiration Glycolysis → Pyruvate Decarboxylation → Citric Acid Cycle → Oxidative Phosphorylation (Electron Transport Chain + ATP synthase) 
Anaerobic Respiration Glycolysis → Lactic Acid Formation or Ethanol Formation 
[show]v • d • eCitric Acid Cycle Metabolic Pathway 
   Oxaloacetate   Malate   Fumarate   Succinate   Succinyl-CoA  
                 
        
Acetyl-CoA   NADH + H+ NAD+  H2O FADH2 FAD CoA + ATP(GTP) Pi + ADP(GDP)  
 + H2O      NADH + H+ + CO2 
  CoA   NAD+ 
     H2O  H2O   NAD(P)+ NAD(P)H + H+   CO2   
        
            
   Citrate   cis-Aconitate   Isocitrate   Oxalosuccinate   α-Ketoglutarate  
 
 
[show]v • d • eMetabolism map 

Glucuronate metabolismPentose interconversionInositol metabolismCellulose and sucrose
metabolismStarch and glycogen
metabolismOther sugar
metabolismPentose phosphate pathwayGlycolysis and GluconeogenesisAmino sugars metabolismSmall amino acid synthesisBranched amino acid
synthesisPurine biosynthesisHistidine metabolismAromatic amino
acid synthesisPyruvate
decarboxylationAnaerobic
respirationFatty acid
metabolismUrea cycleAspartate amino acid
group synthesisPorphyrins and
corrinoids
metabolismCitric acid cycleGlutamate amino
acid group
synthesisPyrimidine biosynthesis v • d • e  All pathway labels on this image are links, simply click to access the article. 
 A high resolution labeled version of this image is available here.  
 
[show]v • d • eMetabolism: Citric acid cycle enzymes 
Cycle Citrate synthase - Aconitase - Isocitrate dehydrogenase - Oxoglutarate dehydrogenase - Succinyl coenzyme A synthetase - Succinate - coenzyme Q reductase (SDHA, SDHB, SDHC, SDHD) - Fumarase - Malate dehydrogenase 
Anaplerotic Pyruvate carboxylase - Aspartate transaminase - Glutamate dehydrogenase - Methylmalonyl-CoA mutase - Pyruvate dehydrogenase complex 


Retrieved from "http://en.wikipedia.org/wiki/Citric_acid_cycle"
Categories: Citric acid cycle | Cellular respiration | Exercise physiology | Metabolic pathways
 Lesson 7
LARYNX 

7-25. INTRODUCTION

The larynx (voice box; "Adams apple") is located in the lower anterior neck region. In many respects, the larynx is different in men and women (sexual dimorphism).

7-26. LARYNX AS A PART OF THE HYOID COMPLEX

The larynx is suspended from the hyoid bone by a membrane. The root of the tongue is attached to the top anterior portion of the hyoid bone. These three structures--the larynx, the hyoid bone, and the tongue--are together known as the hyoid complex. They always move together as a unit.

7-27. GENERAL FUNCTIONS OF THE LARYNX

The larynx performs several functions in humans. 

Its primary function is to control the volume of the air passing through the air passageways, to and from the alveoli of the lungs (para 7-28). 
The larynx also produces selected vibration frequencies in the moving column of air (para 7-29). 
During swallowing, the hyoid complex is raised into the oral cavity. As this happens, the epiglottis of the larynx acts like a trap door, turning down to cover the entrance of the larynx. This prevents swallowed items from entering the lower air passageway, altogether forming the glottis. 
7-28. CONTROL OF VOLUME OF AIR

A pair of folds is found at the bottom of the vestibule of the larynx. These are called the vocal folds or true vocal cords. Extending from front to back, there is one vocal fold on each side. With a special set of muscles, the vocal folds can be drawn apart or pulled together, altogether forming the glottis. 

Thus, the vocal folds are used to control the size of the opening between them, which is called the rima glottidis. When the rima glottidis is wide, air can flow easily between the upper and lower air passageways. When the vocal cords are drawn so tightly that the rima glottidis is completely closed, no air can flow through. 
In Valsalva's maneuver (para 7-9b(4), (5)), the lungs are filled with air and the rima glottidis is closed tightly. The muscles of the trunk wall contract strongly to increase the internal pressure of the trunk. 
(1)  This internal pressure stiffens the trunk into a more rigid structure. Thus, one uses Valsalva's maneuver to provide support for a strenuous effort with the upper members. 
(2)  When Valsalva's maneuver is followed by a sudden opening of the rima glottidis, the result is a cough. This is used to clear the air passageways. 
(3)  An individual whose trunk wall muscles are paralyzed cannot do these things. 
7-29. PRODUCTION OF HUMAN SPEECH

Human speech is a combination of a number of processes. Essentially, a column of air flows out through the oral cavity, where it is chopped into bits of speech known as phonemes. 

Speech sounds produced when the oral cavity is not blocked are called vowels. Sounds resulting from the closing or chopping action of the oral cavity are known as consonants. 
The column of air vibrates at different frequencies (pitch). These vibration frequencies are gained by the air as it passes through the larynx. The pitch is varied by a change in the tension of the vocal cords. The higher the tension, the higher will be the pitch (vibration frequency). 
 
 Lesson 9
LEVELS OF CONTROL IN THE HUMAN NERVOUS SYSTEM

12-31. INTRODUCTION 

General Concept. The human nervous system can be thought of as a series of steps or levels (Figure 12-11). Each level is more complex than the level just below. No level is completely overpowered by upper levels, but each level is controlled or guided by the next upper level as it functions. 
Changes With Development or Injury. 
(1)  Babinski's reflex involves dorsiflexion of the big toe when the sole of the foot is stimulated. It can be normally observed in infants up to 18 months of age. As the pyramidal motor pathways develops completely, this reflex disappears. However, if the pyramidal motor system is injured, the Babinski reflex tends to return. 
(2)  Thus, it is possible to evaluate the extent of development of an individual by identifying the highest level of control. In the case of injury, the highest active level of control helps determine the site of the injury. 


Figure 12-11. Levels of the CNS. 12-32. REFLEXES 

Reflex Arc. The simplest and lowest level of control is the reflex arc. The reflex arc operates essentially on the level of the sensory input. 
Segmental Reflexes. Segmental reflexes produce a wider reaction to a stimulus than the reflex arc. For this purpose, the nervous system is organized more complexly. Thus, information spreads to a wider area of CNS. We can observe a greater reaction to the stimulus. 
12-33. BRAINSTEM "CENTERS"

Within the brainstem, there is a well integrated series of control centers. 

Visceral Centers of the Medulla. There is a group of nuclei in the medulla of the hindbrainstem. Together, these nuclei control the visceral activities of the body, such as respiration, heart beat, etc. 
Reticular Formation. Within the substance of the brainstem is a diffuse system called the reticular formation. The reticular formation has a facilitory (excitatory) area and an inhibitory area. Thus, this control area tends to activate or slow down activities of the body. Thus, it is responsible for producing sleep or wakefulness. 
Hypothalamus and Thalamus. 
(1) The thalamus is a group of nuclei found together in the forebrainstem. The thalamus is the major relay center of sensory inputs from the body. 
(2) The hypothalamus is a higher control center for visceral activities of the body. It is found associated with the thalamus. 
12-34. CEREBELLUM

The cerebellum has been greatly developed, with many functional subdivisions. It is the primary center for the integration and control of patterned, sequential motions of the body. The cerebellum is also the center of control of body posture and equilibrium.

12-35. CEREBRUM

In humans, the highest level of nervous control is localized in the cerebrum. It is at this level that conscious sensation and volitional motor activity are localized. Even so, we can clearly designate three levels of control within the cerebrum: 

Visceral (Vegetative) Level. This level is concerned primarily with visceral activities of the body, as related to fight-or-flight, fear, and other emotions. 
Patterned (Stereotyped) Motor Actions. Here, activities of the body are standardized and repetitive in nature. An example of a stereotyped pattern of muscle activity would be the sequence of muscle actions involved in walking. 
Volitional Level. The volitional level is the highest and newest level of control. Here, cognition (thinking) occurs, and unique, brand-new solutions can be created.
 
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1211.jpg]]
 Lesson 9
LUNGS AND PLEURAL CAVITIES

7-35. INTRODUCTION

In the thoracic cavity is a pair of lungs. Each lung is an individual organ containing the branching elements of one side of the respiratory tree, the connected alveoli, and the corresponding pulmonary NAVL. As with the other organs, the tissues are held together with fibrous connective tissue (FCT). 

The lungs are located within individual serous cavities, called the pleural cavities. The lungs with their pleural cavities constitute the major contents of the thoracic cavity. The pleural cavities help to provide lubrication. 
Located in the middle of the thorax, between the two pleural cavities, is the mediastinum ("I stand between"). The mediastinum is a tissue- and organ-filled space. Within it, the heart (of the blood circulatory system) is located at the same level as the lungs. 
7-36. LUNG STRUCTURE

The two lungs occupy their respective sides of the thoracic cavity. 

The left lung tends to be smaller. This makes room for the extension of the heart into the left side of the thorax. 
In general, the right lung is divided into three major lobes. The left lung is in two major lobes. 
Due to the branching pattern of the respiratory tree (and associated NAVL), each lung consists of broncho pulmonary segments--10 in the right lung and 8 in the left lung. 
7-37. PLEURAL CAVITIES

Surrounding each lung individually is a serous cavity, called the pleural cavity. The minute quantity of serous fluid in the cavity serves as a lubricant. This serves to minimize friction for the expansion and contraction of the lungs during breathing.

a. Each lung is intimately covered with a serous membrane, the visceral pleura.

b. The outer wall of the pleural cavity is lined with another serous membrane known as the parietal pleura. Areas of the parietal pleura are variously named according to their location. 

(1)     The mediastinal pleura forms the lateral wall of the mediastinum. 
(2)     The diaphragmatic pleura covers the superior surface of the diaphragm. 
(3)     The costal pleura lines the inner surface of the rib cage. 
(4)     The cupolar pleura is a dome-like extension into the root of the neck. It contains the apex of the lung. 
c. When each lung is in its smaller volume, its corresponding diaphragmatic pleura lies close to the lower costal pleura. The slit-like cavity between them is called the costophrenic sinus. Fluids of each pleural cavity tend to collect in this sinus, since it is the lowest area for each. When the diaphragm contracts and flattens out, each costophrenic sinus opens up and the inferior portion of the expanding lung occupies this space.
 
http://academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/205Lec.html
http://www.hccfl.edu/facultyinfo/nehringer/bsc1085videolectures.html
 Lesson 2
INTEGUMENT PROPER

3-4. INTRODUCTION

The integument proper has two major parts-the dermis and the epidermis. The dermis (or corium) is made up of rather dense FCT, forming a continuous layer around the body. On top of the dermis is the epidermis. The epidermis and dermis are interlocked by extensions of the dermis up into the epidermis. These extensions are known as papillae.

3-5. LAYERS OF EPIDERMIS

The epidermis is a stratified squamous epithelial tissue. This means that it has several layers of epithelial cells and that its outermost layer is made up of squamous (flat) epithelial cells.

Mitotic Activity. The layer adjacent to the dermis is known as the basal layer. The basal layer is made up of columnar epithelial cells. Since all of the mitotic (cell-multiplying) activity of the epidermis occurs in the basal layer, the basal layer is often called the germinative layer. This mitotic activity involves about 4 percent of the cells in the basal layer at any given time. It occurs primarily between midnight and 0400 hours.

Migration of Cells to the Surface. Over a period of weeks, new cells gradually migrate from the basal layer to the surface. During this migration to the surface, the cells change in shape from the original columnar to cuboidal and then finally to squamous. As the cells become squamous in form, they also become hardened, or cornified, through the development of a special type of protein. As they approach the surface, they die. Thus, the outermost layers of the epidermis are dead, horny scales.

3-6. SPLIT LINES

There are specific lines of tension or stress that varies from one area of the body to the next. The dense FCT of the dermis tends to be oriented along these lines. If a blunt probe is inserted into the dermis, the FCT fibers will separate to form a split. The lines of splits, or split lines, follow the lines of tension in the local area.

3-7. DERMATOGLYPHICS

The surfaces of the palms, soles, and digital pads of the hands and feet are thrown up into ridges and grooves. The patterns formed by these ridges and grooves are called dermatoglyphics. These dermatoglyphics are used as a means of identification, both by law enforcement agencies and by hospitals for newborns. We often refer to such procedures as fingerprinting or foot-printing.

3-8. CREASES

The body is jointed to allow motion. To facilitate motion of the joints, the skin develops natural creases. These creases are in relationship to the joints, but not exactly opposite to the joints.

3-9. THICKNESS

As the continuous covering of the body, the integument proper, or skin, is everywhere. However, the actual thickness of the dermis and/or epidermis varies considerably from very thin to very thick. For example, the thickest skin is located across the back between the shoulders.

3-10. PIGMENTATION

The integument proper of humans has some type of coloration (pigmentation). This coloration is because the presence of special chemicals called pigments. Black, red, and yellow are the most common colors of these pigments.

Development. Special cells are located in the dermis, just below the basal layer of the epidermis. These special cells provide the precursors of the pigments to the basal cells. As these basal cells migrate to the surface, the precursor materials are gradually converted into the actual pigments or colors.

Genetic Control. Genes control the type of color for each individual. There are various genes (sometimes multiple genes) for each color.

When these genes are absent, the individual is an albino. There is a pink glow to the skin and eyes that is produced by the red color of the blood shining through the clear layers of the skin. There is also a whiteness of the skin produced by the refraction of light rays. 
Sometimes, the skin color varies for reasons other than genetic. 
Not only is the color of the integument determined by genes, the pattern of distribution of the color is determined by other genes. 
 
 Lesson 2
TISSUES AND TISSUE PROCESSES OF SKELETAL ELEMENTS

4-3. CONNECTIVE TISSUES

The skeletal elements are made up of several types of connective tissues. In general, connective tissues tend to connect and/or support. These tissues are characterized by an extracellular material referred to as the matrix.

a.      In the formation of the individual organs known as the bones, bone tissues make up the main portion of each bone, on an FCT framework.

b.      Certain bone surfaces are covered with cartilage connective tissue.

4-4. PIEZOELECTRIC EFFECT

a.      Each bone is built around an FCT framework on which the apatite crystals are deposited in a regular order. Apatite is a mineral, a form of calcium phosphate. (Another mineral found in bones is calcium carbonate.)

b.      When compressed, the apatite crystals produce a local electric current. This phenomenon is known as the piezoelectric effect.

c.      Presumably, this piezoelectric effect is produced in the bones of the lower limb during walking. We know that tissues respond to local electric current. When walking casts are used, fractured lower members tend to heal much more rapidly than when the patient is bedridden. Bones tend to lose mass when they are not subjected to forces as great as ordinary.

4-5. BUILDING UP, TEARING DOWN, AND REBUILDING OF BONE TISSUE

a.      The living cells of the bones are osteocytes. When these cells are building up bone tissue, they are called osteoblasts. When they are tearing down bone tissue, they are called osteoclasts.

b.      This building up, tearing down, and rebuilding are continuous processes throughout the life of the individual human being. The building and rebuilding respond specifically to the directions of force applied to the body at that particular time. Therefore, throughout the life of the individual, the skeleton can be remodeled and changed continuously in reaction to applied forces.
 
Lesson 2-4
CELL GROWTH AND MULTIPLICATION

 

2-15. CELL GROWTH

a. The individual cells have the capacity to grow. They do this by acquiring various substances from the blood and converting them into appropriate cellular elements.

b. Sometimes, a tissue such as muscle tissue will increase in mass without an increase in the number of units. This condition is called hypertrophy.

 

2-16. CELL MULTIPLICATION

a. On the other hand, if an increase in tissue mass results from a greater number of cells, we refer to this as hyperplasia.

b. Cell multiplication is accomplished through a process called mitosis. In mitosis, the genetic material of the cell is doubled. Then, the cell divides into halves. One-half of the genetic material goes into each of the two daughter cells. In this manner, the two new cells each have the same genetic composition as the original cell.
Lesson 5
EPITHELIAL CELLS AND TISSUES

2-17. INTRODUCTION

Tissues are groups of like cells together performing a common function or functions. The epithelial tissues are specialized to cover surfaces and line cavities. They are also secretory.

 

 2-18. EPITHELIAL CELL TYPES

By observing microscopic preparations of epithelial tissues, one can classify the cells of epithelial tissues into three general types: columnar, cuboidal, and flat (squamous).

 

2-19. EPITHELIAL TISSUE TYPES

If an epithelial tissue consists of a single layer of cells, it is called a simple epithelial tissue. When there are several layers of cells, it is called a stratified epithelial tissue. In both cases, the epithelial tissue is further identified by the type of epithelial cell that forms the outermost layer of the tissue. For example, the outer layer (epidermis) of the skin is a stratified squamous epithelium; squamous cells form the outermost of many layers.

 

2-20. LINING OF SEROUS CAVITIES

The many serous cavities of the body are lined with a simple squamous epithelium. This epithelial tissue also secretes a serous fluid to act as a lubricant, reducing frictional forces of organs moving against each other. An example is the outer surfaces of the lungs, which move on the inside of the chest wall (within the pleural cavity) during breathing.

 

2-21. OUTER SURFACE OF THE BODY

The outer layer of the skin is a stratified squamous epithelium. In it, there are many layers of cells. The outermost layers consist of squamous, or flat, cells.

 

2-22. SECRETORY PROCESSES

Secretory epithelial cells, such as those in various glands, have a well-developed Golgi complex. In one type of secretory cells, the secretions are passed through the cell membrane. In another type of secretory cells, those of the sebaceous glands, a portion of the cell containing the secretion is sloughed off from the cell.

 
//thanks Simon!
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<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5119523368244429106"><img src="http://lh3.google.com/cardwell.bob/RwwzYQeFQTI/AAAAAAAABaY/6cwVB8w_eqo/s800/illu_long_bone.jpg" /></a></html>
Intramembranous ossification
From Wikipedia, the free encyclopedia
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Osteoblasts and osteoclasts on trabecula of lower jaw of calf embryo. (Kölliker.)Intramembranous ossification is one of two types of bone formation and is the process responsible for the development of flat bones, especially those found in the skull and clavicles. Unlike endochondral ossification, cartilage is not involved or present in this process.

Contents [hide]
1 Overview 
2 Formation of bone spicules 
3 Formation of woven bone 
4 Primary centre of ossification 
5 Formation of osteon 
6 References 
 


[edit] Overview
The first step in the process is the formation of bone spicules which eventually fuse with each other and become trabeculae. The periosteum is formed and bone growth continues at the surface of trabeculae. Much like spicules, the increasing growth of trabeculae result in interconnection and this network is called woven bone. Eventually, woven bone is replaced by lamellar bone.

Process Overview

Mesenchyme cell in the membrane become osteochondral progenitor cell 
osteochondral progenitor cell specialized to become osteoblast 
Osteoblast produce bone matrix and surrounded collagen fiber and become osteocyte 
As the result process trabeculae will develop 
Osteoblast will trap trabeculae to produce bone 
Trabeculae will join together to produce spongy cell 
Cells in the spongy cell will specialize to produce red bone marrow 
Cells surrounding the developing bone will produce periosteum 
Osteoblasts from the Periosteum on the bone matrix will produce compact bone 
jim thome for heisman


[edit] Formation of bone spicules
Embryologic mesenchymal cells (MSC) condense into layers of vascularized primitive connective tissue. Certain mesenchymal cells group together, usually near or around blood vessels, and differentiate into osteogenic cells which deposit bone matrix constitutively. These aggregates of bony matrix are called bone spicules. Separate mesenchymal cells differentiate into osteoblasts, which line up along the surface of the spicule and secrete more osteoid, which increases the size of the spicule.
nYour Results for "Practice Exam" Print this page
 
Site Title:
 Fundamentals of Anatomy & Physiology, Seventh Edition 
Book's Title:
 Fundamentals of Anatomy and Physiology 
Book's Author:
 Martini 
Location on Site: 
 Home > 22: The Lymphatic System and Immunity > Practice Exam 
Date/Time Submitted:
 November 14, 2007 at 8:05 PM (EST)
  
 

--------------------------------------------------------------------------------
 
1.
   The primary responsibility(-ies) of the lymphocytes in the lymphatic system is(are) to respond to the presence of:

Your Answer:
 a, b, and c are correct  
 

--------------------------------------------------------------------------------
 
2.
   The anatomical barriers and defense mechanisms that cannot distinguish one potential threat from another are called:

Your Answer:
 nonspecific defenses  
 

--------------------------------------------------------------------------------
 
3.
   The major components of the lymphatic system include:

Your Answer:
 lymph nodes, lymph, lymphocytes   
Correct Answer:
 lymphatic vessels, lymph, lymphatic organs  
 

--------------------------------------------------------------------------------
 
4.
   The primary function of the lymphatic system is:

Your Answer:
 production, maintenance, and distribution of lymphocytes  
 

--------------------------------------------------------------------------------
 
5.
   Lymphocytes that assist in the regulation and coordination of the immune response are:

Your Answer:
 Helper T and suppressor T cells  
 

--------------------------------------------------------------------------------
 
6.
   Normal lymphocyte populations are maintained through lymphopoiesis in the:

Your Answer:
 bone marrow and lymphatic tissues  
 

--------------------------------------------------------------------------------
 
7.
   The largest collection of lymphoid tissue in the body is contained within the:

Your Answer:
 adult spleen  
 

--------------------------------------------------------------------------------
 
8.
   The protective categories that prevent the approach of, deny entrance to, or limit the spread of microorganisms or other environmental hazards are called:

Your Answer:
 immunological surveillance   
Correct Answer:
 nonspecific defenses  
 

--------------------------------------------------------------------------------
 
9.
   The "first line" of cellular defense against pathogenic invasion is:

Your Answer:
 Phagocytes  
 

--------------------------------------------------------------------------------
 
10.
   NK cells contain the proteins perforin and protectin that provide a type of immunity called:

Your Answer:
 immunological surveillance  
 

--------------------------------------------------------------------------------
 
11.
   The two major ways that the body "carries out" the immune response are:

Your Answer:
 direct attack by T cells and attack by circulating antibodies  
 

--------------------------------------------------------------------------------
 
12.
   A specific defense mechanism is always activated by:

Your Answer:
 an antigen  
 

--------------------------------------------------------------------------------
 
13.
   The type of immunity that develops as a result of natural exposure to an antigen in the environment is:

Your Answer:
 naturally acquired immunity  
 

--------------------------------------------------------------------------------
 
14.
   The fact that people are not subject to the same diseases as goldfish describes the presence of:

Your Answer:
 innate immunity  
 

--------------------------------------------------------------------------------
 
15.
   T-cell activation leads to the formation of cytotoxic T cells and memory T cells that provide:

Your Answer:
 stimulation of inflammation and fever   
Correct Answer:
 cellular immunity  
 

--------------------------------------------------------------------------------
 
16.
   Before an antigen can stimulate a lymphocyte, it must first be processed by a;

Your Answer:
 NK cell   
Correct Answer:
 macrophage  
 

--------------------------------------------------------------------------------
 
17.
   The T cells that limit the degree of immune system activation from a single stimulus are:

Your Answer:
 suppressor T cells   
Correct Answers:
 CD4 T cells 

suppressor T cells  
 

--------------------------------------------------------------------------------
 
18.
   Since each kind of B cell carries its own particular antibody molecule in its cell membrane, activation can only occur in the presence of a(n):

Your Answer:
 corresponding antigen  
 

--------------------------------------------------------------------------------
 
19.
   Activated B cells produce plasma cells that are specialized because they:

Your Answer:
 a, b, and c are correct   
Correct Answer:
 synthesize and secrete antibodies  
 

--------------------------------------------------------------------------------
 
20.
   An active antibody is shaped like a(n):

Your Answer:
 Y  
 

--------------------------------------------------------------------------------
 
21.
   Antibodies may promote inflammation through the stimulation of:

Your Answer:
 basophils and mast cells  
 

--------------------------------------------------------------------------------
 
22.
   The antigenic determinant site is the certain portion of the antigen's exposed surface where:

Your Answer:
 the antibody attacks  
 

--------------------------------------------------------------------------------
 
23.
   In order for an antigenic molecule to be a complete antigen, it must:

Your Answer:
 be immunogenic and reactive  
 

--------------------------------------------------------------------------------
 
24.
   The effect(s) of tumor necrosis factor (TNF) in the body is (are) to:

Your Answer:
 a, b, and c are correct  
 

--------------------------------------------------------------------------------
 
25.
   The ability to demonstrate an immune response upon exposure to an antigen is called:

Your Answer:
 immunological competence  
 

--------------------------------------------------------------------------------
 
26.
   Fetal antibody production is uncommon because the developing fetus has:

Your Answer:
 natural passive immunity  
 

--------------------------------------------------------------------------------
 
27.
   When an immune response mistakenly targets normal body cells and tissues, the result is:

Your Answer:
 an autoimmune disorder  
 

--------------------------------------------------------------------------------
 
28.
   Cells of the immune system influence CNS and endocrine activity by:

Your Answer:
 a, b, and c are correct  
 

--------------------------------------------------------------------------------
 
29.
   Depression of the immune system due to chronic stress may cause:

Your Answer:
 a, b, and c are correct  
 

--------------------------------------------------------------------------------
 
30.
   With advancing age, B cells are less responsive, causing a:

Your Answer:
 a, b, and c are correct   
Correct Answer:
 decreased antibody level after antigen exposure  
 

--------------------------------------------------------------------------------
 
31.
   The three different classes of lymphocytes in the blood are:

Your Answer:
 T cells, B cells, NK cells  
 

--------------------------------------------------------------------------------
 
32.
   The primary effect(s) of complement activation include:

Your Answer:
 a, b, and c are correct  
 

--------------------------------------------------------------------------------
 
33.
   Of the following selections, the one that best defines the lymphatic system is that is it:

Your Answer:
 an integral part of the circulatory system   
Correct Answer:
 a one-way route from the interstitial fluid to the blood  
 

--------------------------------------------------------------------------------
 
34.
   Tissue fluid enters the lymphatic system via the:

Your Answer:
 lymph capillaries  
 

--------------------------------------------------------------------------------
 
35.
   When an antigen appears, the immune system response begins with:

Your Answer:
 the activation of specific T cells and B cells  
 

--------------------------------------------------------------------------------
 
36.
   Systemic evidence of the inflammatory response would include:

Your Answer:
 production of WBCs, fever  
 

--------------------------------------------------------------------------------
 
37.
   Chemical mediators of inflammation include:

Your Answer:
 a, b, and c are correct   
Correct Answer:
 histamine, kinins, prostaglandins, leukotrienes  
 

--------------------------------------------------------------------------------
 
38.
   T lymphocytes comprise approximately __________ percent of circulating lymphocytes.

Your Answer:
 40 - 50   
Correct Answer:
 70 - 80  
 

--------------------------------------------------------------------------------
 
39.
   B lymphocytes differentiate into:

Your Answer:
 memory and plasma cells  
 

--------------------------------------------------------------------------------
 
40.
   __________ cells may activate B cells while _________ cells inhibit the activity of B cells.

Your Answer:
 helper T; suppressor T  
 

--------------------------------------------------------------------------------
 
41.
   The primary response of T-cell differentiation in cell-mediated immunity is the production of __________ cells.

Your Answer:
 suppressor T   
Correct Answer:
 cytotoxic T  
 

--------------------------------------------------------------------------------
 
42.
   The vaccination of antigenic materials into the body is called:

Your Answer:
 artificially acquired passive immunity   
Correct Answer:
 artificially acquired active immunity  
 

--------------------------------------------------------------------------------
 
43.
   In passive immunity __________ are induced into the body by injection.

Your Answer:
 lymphocytes   
Correct Answer:
 antibodies  
 

--------------------------------------------------------------------------------
 
44.
   The lymphatic function of the white pulp of the spleen is:

Your Answer:
 to degrade foreign proteins and toxins released by bacteria   
Correct Answer:
 initiation of immune responses by B cells and T cells  
 

--------------------------------------------------------------------------------
 
45.
   A person with type AB blood has:

Your Answer:
 (blank)
 
 

--------------------------------------------------------------------------------
 
46.
   The antibodies produced and secreted by B lymphocytes are soluble proteins called:

Your Answer:
 immunoglobulins  
 

--------------------------------------------------------------------------------
 
47.
   The genes found in a region called the major histocompatibility complex are called:

Your Answer:
 alpha and gamma interferons   
Correct Answer:
 human leukocyte antigens (HLAs)  
 

--------------------------------------------------------------------------------
 
48.
   Memory B cells do not differentiate into plasma cells unless they:

Your Answer:
 are exposed to the same antigen a second time  
 

--------------------------------------------------------------------------------
 
49.
   The three-dimensional "fit" between the variable segments of the antibody molecule and the corresponding antigenic determinant site is referred to as the:

Your Answer:
 antibody-antigen complex  
 

--------------------------------------------------------------------------------
 
50.
   One of the primary nonspecific effects that glucocorticoids have on the immune response is:

Your Answer:
 inhibition of interleukin secretion   
Correct Answer:
 depression of the inflammatory response  
 
Lymph Nodes
The lymph node is the most organized of the lymphatic organs. Grossly, they're shaped like beans, with a depression on one side, the hilus. Blood vessels enter and leave the lymph node at the hilus, but lymphatic vessels enter at the periphery, and exit at the hilus. More will be said about the flow of lymph through the node below.

Lymph nodes are found along larger lymphatic vessels. The lymphatic vessels, remember, drain tissue fluid back towards the venous circulation. Lymphatic vessels originate as small "blind" structures, i.e., there is no closed loop as there is for the blood circulation. Flow of lymph through these vessels isn't under a continuous pressure the way the blood is; it's "squeezed" back by contraction of muscles around the vessels. The lymph nodes are stationed along these routes to act as "filters" for lymph as it passes through. 

Lymph is pushed through from the periphery of the node to its center, and then continues on its way back to join the venous circulation. Since lymph nodes are pretty sizable organs (most of them are about the size of a pea or larger, some as big as a large broad bean) they need blood vessels and an internal circulation of their own. Blood vessels enter and leave them without releasing blood into the volume of the node, any more than blood is released into other organs.
http://www.acm.uiuc.edu/sigbio/project/updated-lymphatic/lymph1.html
In anatomy, lymph vessels are thin walled, valved structures that carry lymph. As part of the lymphatic system, lymph vessels are complimentary with the vascular system. In contrast to the vascular system, which carries blood under pressure to the entire body, lymph is not under pressure and is propelled in a passive fashion, assisted by the aforementioned valves. Fluid that leaks from the vascular system is returned to general circulation via lymphatic vessels.

Generally, lymph flows away from the tissues to lymph nodes and eventually to either the right lymphatic duct or the largest lymph vessel in the body, the thoracic duct. These vessels drain into the right and left subclavian veins respectively.


 Function
Lymph vessels produce and transport lymph fluid from the tissues to the circulatory system. Without functioning lymph vessels, lymph cannot be effectively drained and edema typically results.

Lymph capillaries or lymphatic capillaries are tiny thin-walled blood vessels that are closed at one end and are located in the spaces between cells throughout the body, except in the central nervous system, and in non-vascular tissues. The main purpose of these vessels is to drain excess tissue fluids from around the cell ready to be filtered and returned to the venous circulation.


Lymphatic capillaries are slightly larger in diameter than blood capillaries and have a unique structure that permits interstitial fluid to flow into them but not out. The ends of endothelial cells that make up the wall of a lymphatic capillary overlap. When pressure is greater in the interstitial fluid than in lymph, the cells separate slightly, like the opening of a one-way swinging door, and interstitial fluid enters the lymphatic capillary. When pressure is greater inside the lymphatic capillary, the cells adhere more closely, and lymph cannot escape back into interstitial fluid. Attached to the lymphatic capillaries are anchoring filaments, which contain elastic fibers. They extend out from the lymphatic capillary, attaching lymphatic endothelial cells to surrounding tissues. When excess interstitial fluid accumulates and causes tissue swelling, the anchoring filaments are pulled, making the openings between cells even larger so that more fluid can flow into the lymphatic capillary.
Lymph node
From Wikipedia, the free encyclopedia
• Interested in contributing to Wikipedia? •Jump to: navigation, search
Lymph node 
 
Structure of the lymph node.1. Efferent lymphatic vessel 2. Sinus 3. Nodule 4. Capsule 5. Medulla 6. Valve to prevent backflow 7. Afferent lymphatic vessel. 
Latin nodus lymphoideus 
Gray's subject #175 688 
MeSH Lymph+nodes 
Dorlands/Elsevier n_09/12576213 
Lymph nodes are components of the lymphatic system. They are sometimes informally called lymph glands but, as they do not secrete substances, such terminology is not accurate. They are found throughout the body.

Lymph nodes are filters or traps for foreign particles and contain white blood cells.

Contents [hide]
1 Function 
2 Structure 
2.1 Cortex 
2.2 Medulla 
2.3 Shape and size 
3 Lymphatic circulation 
4 Distribution 
4.1 Lymph nodes of the human head and neck 
4.2 Lymph nodes of the arm 
4.3 Lower limbs 
5 Additional images 
6 See also 
7 External links 
 


[edit] Function
Lymph nodes act as filters, with an internal honeycomb of reticular connective tissue filled with lymphocytes that collect and destroy bacteria and viruses. When the body is fighting an infection, lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes.


[edit] Structure
The lymph node is surrounded by a fibrous capsule, and inside the lymph node the fibrous capsule extends to form trabeculae. Thin reticular fibers form a supporting meshwork inside the node.

The concave side of the lymph node is called the hilum. The artery and vein attach at the hilum and allows blood to enter and leave the organ, respectively.

The parenchyma of the lymph node is divided into an outer cortex and an inner medulla.


[edit] Cortex
In the cortex, the subcapsular sinus drains to cortical sinusoids.

The outer cortex and inner cortex have very different properties:

Location Name/description Predominant lymphocyte Has nodules? 
outer cortex nodular cortex B cells yes 
deep cortex juxtamedullary cortex or paracortex T cells no 

The cortex is absent at the hilum.

It is made out of the fluid from the blood called plasma.


[edit] Medulla
There are two named structures in the medulla:

The medullary cords are cords of lymphatic tissue, and include plasma cells and T cells 
The medullary sinuses (or sinusoids) are vessel-like spaces separating the medullary cords. Lymph flows to the medullary sinuses from cortical sinuses, and into efferent lymphatic vessels. Medullary sinuses contain histiocytes (immobile macrophages) and reticular cells. 

[edit] Shape and size
Human lymph nodes are bean-shaped and range in size from a few millimeters to about 1-2 cm in their normal state. They may become enlarged due to a tumor or infection. White blood cells are located within honeycomb structures of the lymph nodes. Lymph nodes are enlarged when the body is infected due to enhanced production of some cells and division of activated T and B cells. In some cases they may feel enlarged due to past infections; although one may be healthy, one may still feel them residually enlarged.


[edit] Lymphatic circulation
Lymph circulates to the lymph node via afferent lymphatic vessels and drains into the node just beneath the capsule in a space called the subcapsular sinus. The subcapsular sinus drains into trabecular sinuses and finally into medullary sinuses. The sinus space is criss-crossed by the pseudopods of macrophages which act to trap foreign particles and filter the lymph. The medullary sinuses converge at the hilum and lymph then leaves the lymph node via the efferent lymphatic vessel.

Lymphocytes, both B cells and T cells, constantly circulate through the lymph nodes. They enter the lymph node via the bloodstream and cross the wall of blood vessels by the process of diapedesis.

The B cells migrate to the nodular cortex and medulla. 
The T cells migrate to the deep cortex. 
When a lymphocyte recognizes an antigen, B cells become activated and migrate to germinal centers (by definition, a "secondary nodule" has a germinal center, while a "primary nodule" does not). When antibody-producing plasma cells are formed, they migrate to the medullary cords. Stimulation of the lymphocytes by antigens can accelerate the migration process to about 10 times normal, resulting in characteristic swelling of the lymph nodes.

The spleen and tonsils are large lymphoid organs that serve similar functions to lymph nodes, though the spleen filters blood cells rather than bacteria or viruses.


[edit] Distribution
 
Regional lymph tissueHumans have approximately 500-600 lymph nodes distributed throughout the body, with clusters found in the underarms, groin, neck, chest, and abdomen.


[edit] Lymph nodes of the human head and neck
Cervical lymph nodes 
Anterior cervical: These nodes, both superficial and deep, lie above and beneath the sternocleidomastoid muscles. They drain the internal structures of the throat as well as part of the posterior pharynx, tonsils, and thyroid gland. 
Posterior cervical: These nodes extend in a line posterior to the sternocleidomastoids but in front of the trapezius, from the level of the Mastoid portion of the temporal bone to the clavicle. They are frequently enlarged during upper respiratory infections. 
Tonsillar: (sub mandibular) These nodes are located just below the angle of the mandible. They drain the tonsillar and posterior pharyngeal regions. 
Sub-mandibular: These nodes run along the underside of the jaw on either side. They drain the structures in the floor of the mouth. 
Sub-mental: These nodes are just below the chin. They drain the teeth and intra-oral cavity. 
Supraclavicular lymph nodes: These nodes are in the hollow above the clavicle, just lateral to where it joins the sternum. They drain a part of the thoracic cavity and abdomen. Virchow's node is a left supraclavicular lymph node which receives the lymph drainage from most of the body (especially the abdomen) via the thoracic duct and is thus an early site of metastasis for various malignancies. 

[edit] Lymph nodes of the arm
These drain the whole of the arm, and are divided into two groups, superficial and deep. The superficial nodes are supplied by lymphatics which are present throughout the arm, but are particularly rich on the palm and flexor aspects of the digits.

Superficial lymph glands of the arm: 
supratrochlear glands: Situated above the medial epicondyle of the humerus, medial to the basilic vein, they drain the C7 and C8 dermatomes. 
deltoideopectoral glands: Situated between the pectoralis major and deltoid muscles inferior to the clavicle. 
Deep lymph glands of the arm: These comprise the axillary glands, which are 20-30 individual glands and can be subdivided into: 
lateral glands 
anterior or pectoral glands 
posterior or subscapular glands 
central or intermediate glands 
medial or subclavicular glands 

[edit] Lower limbs
Superficial inguinal lymph nodes 
Deep inguinal lymph nodes 

[edit] Additional images
Lymphatic System

Navigation links

Introduction 
Capillary hydrostatic pressure: fluid diffusion and reabsorption 
Lymph vessels 
Lymph organs: nodes, nodules, spleen, thymus gland, tonsils 
Introduction

As blood circulates, some of its fluid components push out of the capillary bed into the surrounding tissue. This material forms lymph, a special protein-containing tissue fluid that bathes the cells. Lymphatic vessels reabsorb part of this lymph to return it to the circulation, thereby maintaining tissue fluid balance. The lymphatics also engage in absorption of fats and other substances from the digestive tract. Lymph node structures along the route of the lymphatics filter out foreign materials and disease-causing agents from the general circulation. Other lymphatic system structures include the tonsils, spleen, and thymus.

[img[http://www.besthealth.com/besthealth/bodyguide/reftext/images/9604.jpg]]

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Capillary hydrostatic pressure: fluid diffusion and reabsorption

Capillary hydrostatic pressure (filtration pressure) forces fluid out of the blood capillaries. Hydrostatic pressure results from the heart forcing blood through the narrow arterial part of capillaries. The fluid contains oxygen and nutrients that move into the surrounding tissue where they are less concentrated. Similarly, the tissue contains carbon dioxide and waste products that move into the capillaries where they are less concentrated. This process of substances moving from areas of higher concentration to areas of lower concentration is diffusion.

Fluid reabsorption begins in the lymph capillaries that are throughout the body near blood capillaries. Lymph capillaries are small microscopic tubes that collect extracellular fluid. The walls of lymph capillaries comprise loosely joined cells. The overlapping edges of the cells form mini-valves that allow extracellular fluid to pass into the capillary and prevent fluid from flowing back into the tissue. Unlike blood capillaries, lymph capillaries are blind-end tubes that lead away from the tissue.

[img[http://www.besthealth.com/besthealth/bodyguide/reftext/images/9554.jpg]]

Lymph vessels

Lymph travels through the lymph capillaries to small lymph vessels. Like veins, the walls of lymph vessels have smooth muscle that contracts and propels lymph away from the tissues. Lymph vessels contain valves that prevent lymph from flowing backward.

The lymph vessels converge into two main collecting ducts: the shorter right lymphatic duct and the longer thoracic duct. The right lymphatic duct drains lymph from the right side of the head, neck, thorax, and right upper extremity into the right subclavian vein. Lymph from the rest of the body flows into the thoracic duct that empties into the left subclavian vein. The thoracic duct begins in the abdomen as an expanded sac called the cisterna chyli. When lymph empties into the veins, it forms plasma (the liquid part of blood).



Lymph organs: nodes, nodules, spleen, thymus gland, tonsils

The lymphoid organs are the lymph nodes, spleen, thymus, and groups of lymph nodules in both the oral cavity (tonsils) and small intestine, and appendix (Peyer's patches). A connective tissue capsule surrounds the lymph nodes. The nodes have an outer cortex and inner medulla. Within the medulla is the germinal center that produces lymphocytes. These infection-fighting white blood cells produce antibodies that identify and destroy antigens.

[img[http://www.besthealth.com/besthealth/bodyguide/reftext/images/LymphNode.jpg]]

Designed like filters, lymph nodes remove antigens (foreign bodies) from lymph. Each lymph node has several sinuses (inner chambers) that contain lymphocytes. Lymph nodes also contain macrophages that help clear the lymph of bacteria, cellular debris, and other foreign material. Macrophages attack, ingest (engulf), then kill antigens in a process called phagocytosis. Small extensions of the macrophage pull the antigen inside.

 
[img[http://www.besthealth.com/besthealth/bodyguide/reftext/images/Thymus_spleen.jpg]] 

Lymph nodules are groups of lymphocytes arranged in round clusters. Many lymph organs contain lymph nodules within their substances. Unlike lymph nodes, they cannot filter lymph.

The spleen is the largest lymphoid organ. It has two types of tissue: the red pulp, which contains many red blood cells (erythrocytes) and macrophages; and the white pulp, which stores lymphocytes. The macrophages in the red pulp remove foreign substances and damaged or dead erythrocytes and platelets from the blood. And, the red pulp stores platelets, which are important for blood clotting. The lymphocytes within the white pulp are used for the body immune system.

[img[http://www.besthealth.com/besthealth/bodyguide/reftext/images/tonsil.jpg]]

In the thymus gland lymphocytes become specialized. The thymus plays an important role in lymphocyte specialization and immunity.

The tonsils are paired lymph nodules in the oral cavity. These patches of lymph tissue produce lymphocytes. The location of each pair (palatine, pharyngeal, and lingual) determines its name. The tonsils protect the throat and respiratory system. Sometimes, the tonsils cannot remove all the invading microorganisms and become infected. If the infection is severe and chronic, the tonsils may require tonsillectomy (surgical removal).
Lymphatic system
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The human lymphatic systemThe lymphatic system is a complex network of lymphoid organs, lymph nodes, lymph ducts, lymphatic tissues, lymph capillaries and lymph vessels that produce and transport lymph fluid from tissues to the circulatory system. The lymphatic system is a major component of the immune system.

The lymphatic system has three interrelated functions: (1) removal of excess fluids from body tissues, (2) absorption of fatty acids and subsequent transport of fat, as chyle, to the circulatory system and, (3) production of immune cells such as lymphocytes (e.g. antibody producing plasma cells) and monocytes.

Contents [hide]
1 Lymphatic circulation 
2 Function of the fatty acid transport system 
3 Pathology 
4 Development of Lymphatic Tissues 
5 See also 
6 References 
7 External links 
 


[edit] Lymphatic circulation
Unlike the blood system, the lymphatic system is not closed and has no central pump. Lymph movement occurs slowly with low pressure due to peristalsis, valves, and the milking action of skeletal muscles. Like veins, lymph travels through vessels in one way only, due to semilunar valves. This depends mainly on the movement of skeletal muscles to squeeze fluid through them, especially near the joints. Rhythmic contraction of the vessel walls through movements may also help draw fluid into the smallest lymphatic vessels, capillaries. Tight clothing can restrict this, thus reducing the removal of wastes and allowing them to accumulate. If tissue fluid builds up the tissue will swell; this is called edema. As the circular path through the body's system continues, the fluid is then transported to progressively larger lymphatic vessels culminating in the right lymphatic duct (for lymph from the right upper body) and the thoracic duct (for the rest of the body); both ducts drain into the circulatory system at the right and left subclavian veins. The system collaborates with white blood cells in lymph nodes to protect the body from being infected by cancer cells, fungi, viruses or bacteria. This is known as a secondary circulatory system.


[edit] Function of the fatty acid transport system
Lymph vessels called lacteals are present in the lining of the gastrointestinal tract. While most other nutrients absorbed by the small intestine are passed on to the portal venous system to drain, via the portal vein, into the liver for processing, fats (lipids) are passed on to the lymphatic system, to be transported to the blood circulation via the thoracic duct. The enriched lymph originating in the lymphatics of the small intestine is called chyle (not chyme). As the blood circulates, fluid leaks out into the body tissues. This fluid is important because it carries food to the cells and waste back to the bloodstream. The nutrients that are released to the circulatory system are processed by the liver, having passed through the systemic circulation. The lymph system is a one-way system, transporting interstitial fluid back to blood.


[edit] Pathology
In elephantiasis, infection of the lymphatic vessels cause a thickening of the skin and enlargement of underlying tissues, especially in the legs and genitals. It is most commonly caused by a parasitic disease known as lymphatic filariasis.

Lymphedema also causes abnormal swelling, especially in the appendages (though the face, neck, and abdomen can also be affected). It occurs if the lymphatic system is damaged, or underdeveloped in some way. An estimated 170 million suffer with the disorder. There are three stages:
Stage 1: Pressing the swollen limb leaves a pit that takes a while to fill back in. Because there is little fibrosis (hardening) it is often reversible. Elevation reduces swelling.
Stage 2: Pressure does not leave a pit. Elevation does not help. If left untreated, the limb becomes fibrotic.
Stage 3: This stage of lymphedema is often called elephantiasis. It is generally only in the legs after lymphedema that has gone long untreated. While treatment can help a little, it is not reversible.

Some common causes of swollen lymph nodes include staph infections and infectious mononucleosis.


[edit] Development of Lymphatic Tissues
Lymphatic tissues begin to develop by the end of the fifth week of embryonic life. Lymphatic vessels develop from lymph sacs that arise from developing veins, which are derived from mesoderm.
The first lymph sacs to appear are the paired jugular lymph sacs at the junction of the internal jugular and subclavian veins. From the jugular lymph sacs, lymphatic capillary plexuses spread to the thorax, upper limbs, neck and head. Some of the plexuses enlarge and form lymphatic vessels in their respective regions. Each jugular lymph sac retains at least one connection with its jugular vein, the left one developing into the superior portion of the thoracic duct.
The next lymph sac to appear is the unpaired retroperitoneal lymph sac at the root of the mesentery of the intestine. It develops from the primitive vena cava and mesonephric veins. Capillary plexuses and lymphatic vessels spread form the retroperitoneal lymph sac to the abdominal viscera and diaphragm. The sac establishes connections with the cisterna chyli but loses its connections with neighboring veins.
The last of the lymph sacs, the paired posterior lymph sacs, develop from the iliac veins. The posterior lymph sacs produce capillary plexuses and lymphatic vessels of the abdominal wall, pelvic region, and lower limbs. The posterior lymph sacs join the cisterna chyli and lose their connections with adjacent veins.
With the exception of the anterior part of the sac from which the cisterna chyli develops, all lymph sacs become invaded by mesenchymal cells and are converted into groups of lymph nodes.
The spleen develops from mesenchymal cells between layers of the dorsal mesentery of the stomach. The thymus arises as an outgrowth of the third pharyngeal pouch.


[edit] See also
Wikimedia Commons has media related to: 
Lymphatic systemThomas Bartholin and Olaus Rudbeckius, the discoverers of the lymphatic system in humans (David Cantor mentions Gaspare Aselli (1581-1625) as the posthumous discoverer of the lymphatic system. in a 1628 publication). 
History of anatomy in the 17th and 18th centuries 
Lymphedema, a condition of localized fluid retention caused by a compromised lymphatic system 
Lymphoma, a cancer of the tissues in the lymphatic system 
American Society of Lymphology 
Manual lymphatic drainage, a technique claimed to provide health benefits by clearing the lymphatic system. 
Lesson 10
MISCELLANEOUS TOPICS

12-36. CEREBRAL AREAS

Specific areas of the cerebral cortex are concerned with specific parts of the body, with specific types of inputs, and with specific types of activities. Most often, each area is numbered as a specific Brodmann's area. For example, the precentral gyrus, concerned with volitional motions, is Brodmann's area number 4. It is the beginning of the pyramidal motor system. Likewise, the superior temporal gyrus (at the inferior margin of the lateral sulcus) is Brodmann's area number 41; it is the center for hearing.

12-37. DOMINANCE 

About 90% of humans are right-handed. Thus, for these individuals, the left cerebral hemisphere is said to be dominant over the right cerebral hemisphere. 
For 96% of humans, the speech center is located in the left cerebral hemisphere. 
Thus, an injury to the left cerebral hemisphere is generally more serious than an injury to the right cerebral hemisphere. 
12-38. MEMORY 

Memory is that faculty which enables an individual to store and retrieve factual items (sensations, impressions, facts, and ideas). Memory is ultimately the result of the unceasing flow of sensory information into the CNS. These items are stored in the CNS; just exactly how and where is the subject of much research and discussion. All sensory inputs are collated against these stored items in order to arrive at an appropriate action decision. (Often, no action is the most appropriate decision.) 
At present, at least two types of memory are recognized in the human brain--short-term memory and long-term memory. 
(1) Short-term memory. A common example of short-term memory is the ability to hold a phone number in mind for a number of seconds without "memorizing" it. Short-term memory is usually limited to about seven bits of information. 
(2) Long-term memory. A portion of the cerebral cortex known as the hippocampus is thought to be important in transferring information from short-term memory to long-term memory. If the hippocampus is nonfunctional, the individual can learn nothing, but his previously long-term memory remains intact. 
 Lesson 8
MOTOR PATHWAYS IN THE HUMAN NERVOUS SYSTEM

12-28. INTRODUCTION

The CNS receives information through the sensory pathways and collates this information against information stored in memory. This results in a decision. If the decision is to do something, then the CNS sends out commands through the motor pathways to the effector organs (muscles, glands, etc.). 

The motor pathways descend in the neuraxis and transmit the commands to the motor neurons. The processes of motor neurons leave the CNS by way of the peripheral nerves. The somatic motor neurons activate striated muscle fibers. The visceral motor neurons activate smooth muscle tissue, cardiac muscle tissue, and glands. 
We usually consider two general motor pathways--the pyramidal motor pathways and the extrapyramidal motor pathways. 
12-29. PYRAMIDAL MOTOR PATHWAYS

A pyramidal motor pathway is primarily concerned with volitional (voluntary) control of the body parts, particularly with the fine movements of the hands. Since such a pathway is concerned with volitional actions, it is suitable for neurological screening and testing. 

Cerebral Motor Cortex. The pyramidal motor pathway begins in the precentral gyrus of the cerebral hemisphere. As we have already seen with the sensory pathways, the neurons making up the cerebral cortex of the precentral and postcentral gyri are arranged in a pattern (motor homunculus) corresponding to the various parts of the body to which they are connected. 
Motor Neurons. From the precentral gyrus, the axons of these upper motor neurons (UMN) pass into the neuraxis of the CNS and descend. At the level of the appropriate segmental nerve, the UMN synapses either directly or indirectly with a lower motor neuron of the segmental nerve. Direct synapses (monosynaptic) provide the most rapid reactions. Such direct synapses are used in particular for the fine movements of the hands. 
Corticospinal Pathways. The medulla is the lowest part of the brainstem. On the underside of the medulla, the axons of the UMNs form a pair of structures known as the pyramids. Immediately below the pyramids, at the beginning of the spinal cord, the axons cross to the opposite side of the CNS (spinal cord). The axons then descend as the lateral corticospinal tract, within the lateral funiculus (Figure 12-6). Thus, the left cerebral hemisphere commands the right side of the body, and the right cerebral hemisphere controls the left side of the body. 
12-30. EXTRAPYRAMIDAL MOTOR PATHWAYS

The extrapyramidal motor pathways are concerned with automatic (nonvolitional) control of body parts. This particularly includes patterned, sequential movements or actions. Thus, the major command system of the human nervous system uses these pathways. There are several extrapyramidal motor pathways. Having multisynaptic circuits throughout the CNS, they use many intermediate relays before reaching the effector organs. The cerebellum of the brain plays a major role in extrapyramidal pathways; the cerebellum is the major center for coordinating the patterned sequential actions of the body, such as walking.
 
MUSCULAR SYSTEM DISORDERS

Botulism (BOCH-a-liz-em): Form of food poisoning in which a bacterial toxin prevents the release of acetylcholine at neuromuscular junctions, resulting in paralysis.

Muscular dystrophy (MUS-kyu-lar DIS-tro-fee): One of several inherited muscular diseases in which a person's muscles gradually and irreversibly deteriorate, causing weakness and eventually complete disability.

Myasthenia gravis (my-ass-THEH-nee-ah GRA-vis): Autoimmune disease in which antibodies attack acetylcholine, blocking the transmission of nerve impulses to muscle fibers.

Tetanus (TET-n-es): Bacterial disease in which a bacterial toxin causes the repetitive stimulation of muscle fibers, resulting in convulsive muscle spasms and rigidity.

The first symptom of this disease type is clumsiness in walking and a tendency to fall due to muscle weakness in the legs and pelvis. The disease then spreads to other areas in the body. Sometimes, muscle tissue is replaced by fatty tissue, giving the false impression that the muscles have become enlarged. By the age of ten, a boy is usually confined to a wheelchair or a bed. Death usually occurs before adulthood because of a respiratory infection brought on by the weakness of respiratory or breathing muscles.

Another type of muscular dystrophy appears later in life and affects both sexes equally. The first signs appear in adolescence. The muscles affected are those in the face, shoulders, and upper arms. The hips and legs may also be affected. This type of muscular dystrophy occurs in about 1 out of every 20,000 people. Individuals afflicted with this disease may survive until middle age.

Currently, there is no known cure for any type of muscular dystrophy. Certain drugs have been developed that slow the progression of some types. Physical therapy involving regular, nonstrenuous exercise is often prescribed to help maintain general good health.

Myasthenia gravis
Myasthenia gravis is an autoimmune disease that causes muscle weakness. An autoimmune disease is one in which antibodies (proteins normally produced by the body to fight infection) attack and damage the body's own normal cells, causing tissue destruction. In myasthenia gravis, antibodies attack receptors on the membranes of muscle fibers that receive acetylcholine from motor neurons. Unable to receive acetylcholine, the muscle fibers cannot be stimulated to contract and weakness develops.

About 30,000 people in the United States are affected by myasthenia gravis. The disease can occur at any age, but it is most common in women between the ages of twenty and forty. The muscles of the neck, throat, lips, tongue, face, and eyes are primarily affected. Muscles of the arms, legs, and trunk may also be involved. Depending on the severity of the disease, a person may have difficulty moving their eyes, seeing clearly, walking, speaking clearly, chewing and swallowing, and even breathing. Physical exertion, heat from the Sun, hot showers, hot drinks, and stress may all increase symptoms.

There is no cure for myasthenia gravis, but drugs have been developed that effectively control the symptoms in most people. The disease only causes early death if the respiratory muscles are affected and stop functioning properly.


 
An intramuscular injection. Medication is injected into muscles when larger volumes of a drug are needed. (Reproduced by permission of Photo Researchers, Inc.) 

Spasms and cramps
Muscle spasms and cramps are spontaneous, often painful muscle contractions. Cramps are usually defined as spasms that last over a period of time. Any muscle in the body may be affected, but spasms and cramps are most common in the calves, feet, and hands. While painful, spasms and cramps are harmless and are not related to any disorder, in most cases.

Spasms or cramps may be caused by abnormal activity at any stage in the muscle contraction process, from the brain sending an electrical signal to the muscle fiber relaxing. Prolonged exercise, where sensations of pain and fatigue are often ignored, can lead to such severe energy shortages that a muscle cannot relax, causing a spasm or cramp. Dehydration—the loss of fluids and salts through sweating, vomiting, or diarrhea—can disrupt ion balances in both muscles and nerves. This can prevent them from responding and recovering normally, which can lead to spasms and cramps.

Most simple spasms and cramps require no treatment other than patience and stretching. Gentle stretching and massaging of the affected muscle may ease the pain and hasten recovery.

Strains
Strains are tears in a muscle. Sometimes called pulled muscles, they usually occur because of overexertion (too much tension placed on a muscle) or improper lifting techniques. Strains are common and can affect anyone. Symptoms of strains range from mild muscle stiffness to great soreness.

Mild strains can be treated at home. Basic first aid consists of RICE: R est, I ce for forty-eight hours, C ompression (wrapping in an elastic bandage), and E levation. Strains can be prevented by stretching and warming up before exercising and using proper lifting techniques.

Tetanus
Like botulism, tetanus is also caused by a toxin released by a bacteria. This bacteria invades the body most often through deep puncture wounds exposed to contaminated soil. Many people associate tetanus with wounds from rusty nails or other dirty objects, but any wound can be a source. In the body, the tetanus bacteria releases its toxin, which affects motor neurons at neuromuscular junctions. Its effect, however, is opposite that of the botulism toxin. This toxin causes the repetitive stimulation of muscle fibers, resulting in convulsive muscle spasms and rigidity.

Tetanus is often called "lockjaw" because one of the most common symptoms is a stiff jaw, unable to be opened. The disease sometimes affects the body only at the site of infection. More often, it spreads to the entire body. The uncontrollable muscle spasms produced are sometimes severe enough to cause broken bones. Tetanus results in death when the muscles controlling breathing become "locked" and cannot function.

Up to 30 percent of tetanus victims in the United States die. Prompt medical attention is crucial in handling the disease. Treatment, which can take several weeks, includes antibiotics to kill the bacteria and shots of antitoxin to neutralize the toxin. Recovery can then take six or more weeks. Tetanus, however, is easily preventable through vaccination, which helps the body develop antibodies against the bacteria.
[[Bob's Place]]

[[Anatomy and Physiology 101]]

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The medulla oblongata is the lower portion of the brainstem.

[img[http://upload.wikimedia.org/wikipedia/commons/2/2b/Illu_cerebrum_lobes.jpg]]

Location

By anatomical terms of location, it is rostral to the spinal cord and caudal to the pons, which is in turn ventral to the cerebellum.

For a human or other bipedal species, this means it is above the spinal cord, below the pons, and anterior to the cerebellum.

 Anatomy

Two parts: open and closed

The medulla is often thought of as being in two parts:

    * an open part (close to the pons)
    * a closed part (further down towards the spinal cord).

The opening referred to is on the dorsal side of the medulla, and forms part of the fourth ventricle of the brain.

 Landmark fissures and sulci

The medulla has an anterior median fissure and a posterior median sulcus corresponding to the structures seen in the spinal cord.

On each side, the anterolateral sulcus lies in line with the ventral roots of the spinal nerves. The rootlets of cranial nerve XII (the hypoglossal nerve) emerge from this sulcus.

The posterolateral sulcus lies in line with the dorsal roots of the spinal nerves. It gives attachment to the rootlets of the glossopharyngeal, vagus and the accessory nerve or the IX, X, and the XI cranial nerves from above downward in order.

Between the anterior median sulcus and the anterolateral sulcus

The region between the anterior median sulcus and the anterolateral sulcus is occupied by an elevation on either side called as the pyramid of medulla oblongata. This elevation is caused by the corticospinal tract.

In the lower part of the medulla some of these fibers cross each other thus obliterating the anterior median fissure. This is known as the decussation of the pyramids.

Some other fibers that originate from the anterior median fissure above the decussation of the pyramids and run laterally across the surface of the pons are known as the external arcuate fibers.

[edit] Between the anterolateral and posterolateral sulci

The region between the anterolateral and posterolateral sulci in the upper part of the medulla is marked by a swelling known as the olive.

It is caused by a large mass of gray matter known as the inferior olivary nucleus.

 Between the posterior median sulcus and the posterolateral sulcus

The posterior part of the medulla between the posterior median sulcus and the posterolateral sulcus contains tracts that enter it from the posterior funiculus of the spinal cord. These are the fasciculus gracilis, lying medially next to the midline, and the fasciculus cuneatus, lying laterally.

These fasciculi end in rounded elevations known as the gracile and the cuneate tubercles. They are caused by masses of gray matter known as the nucleus gracilis and the nucleus cuneatus.

Just above the tubercles, the posterior aspect of the medulla is occupied by a triangular fossa, which forms the lower part of the floor of the fourth ventricle. The fossa is bounded on either side by the inferior cerebellar peduncle, which connects the medulla to the cerebellum.

Lower part

The lower part of the medulla, immediately lateral to the fasciculus cuneatus, is marked by another longitudinal elevation known as the tuberculum cinereum.

It is caused by an underlying collection of gray matter known as the spinal nucleus of the trigeminal nerve.

The gray matter of this nucleus is covered by a layer of nerve fibers that form the spinal tract of the trigeminal nerve.

Base

The base of the medulla is defined by the commissural fibers, crossing over from the ipsilateral side in the spinal cord to the contralateral side in the brain stem; below this is the spinal cord.


Functions

The medulla oblongata controls autonomic functions, and relays nerve signals between the brain and spinal cord. It is also responsible for controlling several major autonomic functions of the body:

    * respiration (via dorsal respiratory group and ventral respiratory group)
    * blood pressure
    * heart rate
    * reflex arcs
    * vomiting
    * defecation

 Blood supply

Blood to the medulla is supplied by a number of arteries.

    * Anterior spinal artery: The anterior spinal artery supplies the whole medial part of the medulla oblongata. A blockage (such as in a stroke) will injure the pyramidal tract, medial lemniscus, and the hypoglossal nucleus. This causes a syndrome called medial medullary syndrome.
    * Posterior inferior cerebellar artery (PICA): The posterior inferior cerebellar artery, a major branch of the vertebral artery, supplies the posterolateral part of the medulla, where the main sensory tracts run and synapse. (As the name implies, it also supplies some of the cerebellum.)
    * Direct branches of the vertebral artery: The vertebral artery supplies an area between the other two main arteries, including the nucleus solitarius and other sensory nuclei and fibers. Lateral medullary syndrome can be caused by occlusion of either the PICA or the vertebral arteries.
    * (ceribellar artery is suppelyed by the medulla)
[img[http://upload.wikimedia.org/wikipedia/commons/2/2b/Illu_cerebrum_lobes.jpg]]
http://en.wikipedia.org/wiki/Meninges


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Meninges
From Wikipedia, the free encyclopedia
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Meninges 
 
Meninges of the CNS 
Gray's subject #193 872 
Artery middle meningeal artery, meningeal branches of the ascending pharyngeal artery, accessory meningeal artery, branch of anterior ethmoidal artery, meningeal branches of vertebral artery 
Nerve middle meningeal nerve, nervus spinosus 
MeSH Meninges 
Dorlands/Elsevier m_09/12523818 
The meninges (singular meninx) is the system of membranes which envelop the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.

Contents [hide]
1 Anatomy 
1.1 Pia mater 
1.2 Arachnoid mater 
1.3 Dura mater 
1.4 Spaces 
2 Pathology 
3 Additional images 
4 References 
 


[edit] Anatomy

[edit] Pia mater
The pia or pia mater is a very delicate membrane. It is attached to (nearest) the brain or the spinal cord. As such it follows all the minor contours of the brain (gyri and sulci). The pia mater is the meningeal envelope which firmly adheres to the surface of the brain and spinal cord. It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel to the brain and spinal cord, and its capillaries are responsible for nourishing the brain.


[edit] Arachnoid mater
The middle element of the meninges is the arachnoid mater, so named because of its spider web-like appearance. It provides a cushioning effect for the central nervous system. The arachnoid mater exists as a thin, transparent membrane. It is composed of fibrous tissue and, like the pia mater, is covered by flat cells also thought to be impermeable to fluid. The arachnoid does not follow the convolutions of the surface of the brain and so looks like a loosely fitting sac. In the region of the brain, particularly, a large number of fine filaments called arachnoid trabeculae pass from the arachnoid through the subarachnoid space to blend with the tissue of the pia mater.

The arachnoid and pia mater are sometimes together called the leptomeninges.


[edit] Dura mater
The dura mater (also rarely called meninx fibrosa, or pachymeninx) is a thick, durable membrane, closest to the skull. It contains larger blood vessels which split into the capilliaries in the pia mater. It is composed of dense fibrous tissue, and its inner surface is covered by flattened cells like those present on the surfaces of the pia mater and arachnoid. The dura mater is a sac which envelops the arachnoid and has been modified to serve several functions. The dura mater surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart.


[edit] Spaces
The subarachnoid space is the space which normally exists between the arachnoid and the pia mater, which is filled with cerebrospinal fluid.

Normally, the dura mater is attached to the skull in the head, or to the bones of the vertebral canal in the spinal cord. The arachnoid is attached to the dura mater, and the pia mater is attached to the central nervous system tissue. When the dura mater and the arachnoid separate through injury or illness, the space between them is the subdural space.


[edit] Pathology
There are three types of hemorrhage involving the meninges:[1]

A subarachnoid hemorrhage is acute bleeding under the arachnoid; it may occur spontaneously or as a result of trauma. 
A subdural hematoma is a hematoma (collection of blood) located in a separation of the arachnoid from the dura mater. The small veins which connect the dura mater and the arachnoid are torn, usually during an accident, and blood can leak into this area. 
An epidural hematoma similarly may arise after an accident or spontaneously. 
Other medical conditions which affect the meninges include meningitis (usually from fungal, bacterial, or viral infection) and meningiomas arising from the meninges or from tumors formed elsewhere in the body which metastasize to the meninges.


[edit] Additional images

Diagrammatic representation of a section across the top of the skull



 
Diagrammatic section of scalp.



 


 


[edit] References
^ Orlando Regional Healthcare, Education and Development. 2004. "Overview of Adult Traumatic Brain Injuries." Retrieved on September 6, 2007. 
[hide]v • d • eAnatomy: meninges of the brain and medulla spinalis 
Layers Dura mater (Falx cerebri, Tentorium cerebelli, Falx cerebelli) • Arachnoid mater (Arachnoid granulation) • Subarachnoid space • Pia mater 
Cisterns Cisterna magna • Pontine cistern • Interpeduncular cistern • Chiasmatic • Lateral cerebral fossa • Great cerebral vein 
Other Cerebrospinal fluid 

Retrieved from "http://en.wikipedia.org/wiki/Meninges"
Categories: Back anatomy | Head and neck | Central nervous system | Meninges
MITOSIS: 

Prophase: 
Nucleoli disappear 
Centrosomes split and each daughter forms an aster. 
Prometaphase 
The Nuclear Envelope breaks down. 
Microtubules from each centrosome start interacting with the chromosomes. 
Kinetochore Microtubules from the centromere of each chromosome mature and attach to some of the spindle microtubules. 
Metaphase 
The Kinetochore microtubules align the chromosomes along the metaphase plate. 
The chromosomes are held in place by the opposed kinetochores and their associated microtubules. 
Anaphase 
Kinetochores on each chromosome separate, allowing each chromatid to be pulled toward the poles. 
Anaphase-A: Kinetochore Microtubules shorten. Since the plus end of these microtubules is right at the centromere, this shortening causes the chromosomes to be pulled toward the poles. 
Anaphase-B: Polar Microtubules elongate. The plus end of the polar microtubules face the equator too, but this elongation somehow aids in pulling (or pushing) the poles apart. 
Ca+2 seems to play a role in promoting anaphase. There is high Ca+2 concentration during anaphase. 
Telophase: 
Daughter chromatids reach the poles. 
Kinetochore microtubules disappear. 
Nuclear envelope reforms as nuclear lamins reassociate, condensed chromatin expands, and nucleoli reappear. 
Involves dephosphorylation of many proteins. 
Cytokinesis. 
Actin and Myosin pinch the cell and form a contractile ring. 
Organelles and cytoplasm are distributed evenly. 
http://en.wikipedia.org/wiki/Mucous_membranes

[img[http://upload.wikimedia.org/wikipedia/en/4/4e/Ens.png]]

[img[http://upload.wikimedia.org/wikipedia/commons/e/e7/Illu_ureters_wall.jpg]]

Types of mucosa (incomplete)

Buccal mucosa 
Gastric mucosa 
Intestinal mucosa 
Olfactory mucosa 
Oral mucosa 
bronchial mucosa 
Endometrium is the mucosa of the uterus 

Mucous membrane
From Wikipedia, the free encyclopedia
(Redirected from Mucous membranes)• Ten things you didn't know about Wikipedia •Jump to: navigation, search
Mucous membrane 
 
LAYERS:
serosa
longitudinal muscle
myenteric plexus
circular muscle
submucosal plexus
submucosal
mucosal 
 
Section of the human esophagus. Moderately magnified. The section is transverse and from near the middle of the gullet.
a. Fibrous covering.
b. Divided fibers of longitudinal muscular coat.
c. Transverse muscular fibers.
d. Submucous or areolar layer.
e. Muscularis mucosae.
f. Mucous membrane, with vessels and part of a lymphoid nodule.
g. Stratified epithelial lining.
h. Mucous gland.
i. Gland duct.
m’. Striated muscular fibers cut across. 
Latin tunica mucosa 
Gray's subject #242 1110 
Dorlands/Elsevier t_22/12831913 
The mucous membranes (or mucosae; singular: mucosa) are linings of mostly endodermal origin, covered in epithelium, and are involved in absorption and secretion. They line various body cavities that are exposed to the external environment and internal organs. It is at several places continuous with skin: at the nostrils, the lips, the ears, the genital area, and the anus. The sticky, thick fluid secreted by the mucous membranes and gland is termed mucus. The term mucous membrane refers to where they are found in the body and not every mucous membrane secretes mucus.

Body cavities featuring mucous membrane include most of the respiratory system. The glans penis (head of the penis) and glans clitoridis and the inside of the prepuce (foreskin) and clitoral hood are mucous membranes, not skin.

Contents [hide]
1 Components 
2 Types of mucosa (incomplete) 
3 Additional images 
4 See also 
5 External links 
 


[edit] Components
Epithelium 
Lamina propria 
Smooth muscle/Muscularis mucosa/ (GI tract) 

[edit] Types of mucosa (incomplete)
Buccal mucosa 
Gastric mucosa 
Intestinal mucosa 
Olfactory mucosa 
Oral mucosa 
bronchial mucosa 
Endometrium is the mucosa of the uterus 

[edit] Additional images

Wall of the ureter.



 
Section of mucous membrane of human stomach, near the cardiac orifice.



 


[edit] See also
Mucin 
Mucocutaneous boundary 

[edit] External links
mucosa at eMedicine Dictionary 
Organology at UC Davis Digestive/mammal/system1/system4 - "Mammal, whole system (LM, Low)" 
MeSH Mucous+Membrane 
[hide]v • d • etissue layers 
mesothelium, serosa/adventitia, muscularis externa (outer & inner), submucosa, mucosa (muscularis mucosa, lamina propria, epithelium), lumen 
MUSCLE FACTS
Smallest muscle in the body?

Stapedius: the muscle that activates the stirrup, the small bone that sends vibrations from the eardrum to the inner ear. It measures just 0.05 inch (0.13 centimeter) in length.

Largest muscle in the body?

Latissimus dorsi: the large, flat muscle pair that covers the middle and lower back.

Longest muscle in the body?

Sartorius: the straplike muscle that runs diagonally from the waist down across the front of the thigh to the knee.

Strongest muscle in the body?

Gluteus maximus: the muscle pair of the hip that form most of the flesh of the buttocks.

Fastest-reacting muscle in the body?

Orbicularis oculi: the muscle that encircles the eye and closes the eyelid. It contracts in less than 0.01 second.

Number of muscles used to make a smile?

Seventeen.

Number of muscles used to make a frown?

Forty-three.
The Muscular System: Words to Know
Acetylcholine (ah-see-til-KOE-leen):Neurotransmitter chemical released at the neuromuscular junction by motor neurons that translates messages from the brain to muscle fibers. 
Adenosine triphosphate (ah-DEN-o-seen try-FOS-fate):High-energy molecule found in every cell in the body. 
Aerobic metabolism (air-ROH-bic muh-TAB-uhlizm):Chemical reactions that require oxygen in order to create adenosine triphosphate. 
Antagonist (an-TAG-o-nist):Muscle that acts in opposition to a prime mover. 
Cramp:Prolonged muscle spasm. 
Fascicle (FA-si-kul):Bundle of myofibrils wrapped together by connective tissue. 
Lactic acid (LAK-tik ASS-id):Chemical waste product created when muscle fibers break down glucose without the proper amount of oxygen. 
Muscle tone:Sustained partial contraction of certain muscle fibers in all muscles. 
Myofibrils (my-o-FIE-brilz):cylindrical structures lying within skeletal muscle fibers that are composed of repeating structural units called sarcomeres. 
Myofilament (my-o-FILL-ah-ment):Protein filament composing the myofibrils; can be either thick (composed of myosin) or thin (composed of actin). 
Neuromuscular junction (nu-row-MUSS-ku-lar-JUNK-shun):Region where a motor neuron comes into close contact with a muscle fiber. 
Prime mover (or agonist):Muscle whose contractions are chiefly responsible for producing a particular movement. 
Rigor mortis (RIG-er MOR-tis):Rigid state of the body after death due to irreversible muscle contractions. 
Sarcomere (SAR-koh-meer):Unit of contraction in a skeletal muscle fiber containing a precise arrangement of thick and thin myofilaments. 
Spasm:Sudden, involuntary muscle contraction. 
Strain:Slight tear in a muscle; also called a pulled muscle. 
Synergist (SIN-er-jist):Muscle that cooperates with another to produce a particular movement. 
Tendon (TEN-den):Tough, white, cordlike tissue that attaches muscle to bone. 
Cardiac muscle, called the myocardium, is found in only one place in the body: the heart. It is a unique type of muscle. Like skeletal muscle, it is
http://images.google.com/imgres?imgurl=http://www.sport-fitness-advisor.com/images/muscular_system_picture_front.jpg&imgrefurl=http://www.sport-fitness-advisor.com/muscular-system-picture.html&h=667&w=475&sz=54&tbnid=0w6CUrNWOVrYUM:&tbnh=138&tbnw=98&prev=/images%3Fq%3Dmuscle%2Bsystem%26um%3D1&start=1&ei=xOwWR8jLGJuAigGV9LySBw&sig2=6xNGOXRmHhGc8ZtN70frsw&sa=X&oi=images&ct=image&cd=1

http://images.google.com/imgres?imgurl=http://www.sport-fitness-advisor.com/images/muscular_system_diagram_back.jpg&imgrefurl=http://www.sport-fitness-advisor.com/muscular-system-diagram.html&h=633&w=486&sz=54&tbnid=IWttOVWUmg-AyM:&tbnh=137&tbnw=105&prev=/images%3Fq%3Dmuscle%2Bsystem%26um%3D1&start=2&ei=xOwWR8jLGJuAigGV9LySBw&sig2=tPNYC6B2aqOJTAwHGdQtng&sa=X&oi=images&ct=image&cd=2

http://www.innerbody.com/image/musfov.html


http://www.getbodysmart.com/ap/muscularsystem/menu/menu.html

http://en.wikipedia.org/wiki/Muscular_system

http://en.wikipedia.org/wiki/Sinus_node

http://webschoolsolutions.com/patts/systems/muscles.htm


http://www.einsteins-emporium.com/human-anatomy/sh370.htm

http://www.faqs.org/health/Body-by-Design-V1/The-Muscular-System.html

http://www.ptcentral.com/muscles/

http://www.wiley.com/college/apcentral/anatomydrill/

http://science.nhmccd.edu/biol/ap1int.htm
http://en.wikipedia.org/wiki/Muscle

Muscle
From Wikipedia, the free encyclopedia
• Ten things you didn't know about images on Wikipedia •Jump to: navigation, search
 
A top-down view of skeletal muscleMuscle (from Latin musculus "little mouse" [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. It is classified as skeletal, cardiac, or smooth muscle[2], and its function is to produce force and cause motion, either locomotion or movement within internal organs. Much of muscle contraction occurs without conscious thought and is necessary for survival, like the contraction of the heart, or peristalsis (which pushes food through the digestive system). Voluntary muscle contraction is used to move the body, and can be finely controlled, like movements of the eye, or gross movements like the quadriceps muscle of the thigh. There are two broad types of voluntary muscle fibers, slow twitch and fast twitch. Slow twitch fibers contract for long periods of time but with little force while fast twitch fibers contract quickly and powerfully but fatigue very rapidly.

Contents [hide]
1 Types 
2 Anatomy 
2.1 Macroanatomy 
2.2 Microanatomy 
3 Physiology 
4 Nervous control 
4.1 Efferent leg 
4.2 Afferent leg 
5 Role in health and disease 
5.1 Exercise 
5.2 Disease 
5.2.1 Atrophy 
6 Strength 
6.1 The 'strongest' human muscle 
7 Efficiency 
8 Muscle evolution 
9 References 
9.1 Notes 
10 See also 
11 External links 
 


Types
 
Types of muscleThere are three types of muscle:

Skeletal muscle or "voluntary muscle" is anchored by tendons to bone and is used to affect skeletal movement such as locomotion and in maintaining posture. Though this postural control is generally maintained as a subconscious reflex, the muscles responsible react to conscious control like non-postural muscles. An average adult male is made up of 40-50% of skeletal muscle and an average adult female is made up of 30-40%. 
Smooth muscle or "involuntary muscle" is found within the walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra, bladder, and blood vessels, and unlike skeletal muscle, smooth muscle is not under conscious control. 
Cardiac muscle is also an "involuntary muscle" but is a specialized kind of muscle found only within the heart. 
Cardiac and skeletal muscle are "striated" in that they contain sarcomeres and are packed into highly-regular arrangements of bundles; smooth muscle has neither. While skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles. Striated muscle contracts and relaxes in short, intense bursts, whereas smooth muscle sustains longer or even near-permanent contractions.

Skeletal muscle is further divided into several subtypes:

Type I, slow oxidative, slow twitch, or "red" muscle is dense with capillaries and is rich in mitochondria and myoglobin, giving the muscle tissue its characteristic red color. It can carry more oxygen and sustain aerobic activity. 
Type II, fast twitch, muscle has three major kinds that are, in order of increasing contractile speed:[3] 
Type IIa, which, like slow muscle, is aerobic, rich in mitochondria and capillaries and appears red. 
Type IIx (also known as type IId), which is less dense in mitochondria and myoglobin. This is the fastest muscle type in humans. It can contract more quickly and with a greater amount of force than oxidative muscle, but can sustain only short, anaerobic bursts of activity before muscle contraction becomes painful (often incorrectly attributed to a build-up of lactic acid). N.B. in some books and articles this muscle in humans was, confusingly, called type IIB.[4] 
Type IIb, which is anaerobic, glycolytic, "white" muscle that is even less dense in mitochondria and myoglobin. In small animals like rodents this is the major fast muscle type, explaining the pale color of their flesh. 

Anatomy
The anatomy of muscles includes both macroanatomy, comprising all the muscles of an organism, and, on the other hand, microanatomy, which comprises the structures of a single muscle.


Macroanatomy
Main article: list of muscles of the human body
There are approximately 639 skeletal muscles in the human body. Contrary to popular belief, the number of muscle fibres cannot be increased through exercise; instead the muscle cells simply get bigger. Muscle fibres have a limited capacity for growth through hypertrophy and some believe they split through hyperplasia if subject to increased demand.


Microanatomy
Muscle is mainly composed of muscle cells. Within the cells are myofibrils; myofibrils contain sarcomeres, which are composed of actin and myosin. Individual muscle fibres are surrounded by endomysium. Muscle fibers are bound together by perimysium into bundles called fascicles; the bundles are then grouped together to form muscle, which is enclosed in a sheath of epimysium. Muscle spindles are distributed throughout the muscles and provide sensory feedback information to the central nervous system.

Skeletal muscle is muscle attached to skeletal tissue, distinct from heart or smooth muscle. It is arranged in discrete muscles, an example of which is the biceps brachii. It is connected by tendons to processes of the skeleton. In contrast, smooth muscle occurs at various scales in almost every organ, from the skin (in which it controls erection of body hair) to the blood vessels and digestive tract (in which it controls the caliber of the lumen and peristalsis). Cardiac muscle is the muscle tissue of the heart, and is similar to skeletal muscle in both composition and action, being comprised of myofibrils of sarcomeres. Cardiac muscle is anatomically different in that the muscle fibers are typically branched like a tree branch, and connect to other cardiac muscle fibers through intercalcated discs, and form the appearance of a syncytium.


Physiology
Main article: muscle contraction
The three (skeletal, cardiac and smooth) types of muscle have significant differences. However, all three use the movement of actin against myosin to create contraction. In skeletal muscle, contraction is stimulated by electrical impulses transmitted by the nerves, the motor nerves and motoneurons in particular. Cardiac and smooth muscle contractions are stimulated by internal pacemaker cells which regularly contract, and propagate contractions to other muscle cells they are in contact with. All skeletal muscle and many smooth muscle contractions are facilitated by the neurotransmitter acetylcholine.

Muscular activity accounts for much of the body's energy consumption. All muscle cells produce adenosine triphosphate (ATP) molecules which are used to power the movement of the myosin heads. Muscles contain ATP in the form of creatine phosphate which is generated from ATP and can regenerate ATP when needed with creatine kinase. Muscles also keep a storage form of glucose in the form of glycogen. Glycogen can be rapidly converted to glucose when energy is required for sustained, powerful contractions. Within the voluntary skeletal muscles, the glucose molecule is metabolized in a process called glycolysis which produces two ATP and two lactic acid molecules in the process. Muscle cells also contain globules of fat, which are used for energy during aerobic exercise. The aerobic energy systems take longer to produce the ATP and reach peak efficiency, and requires many more biochemical steps, but produces significantly more ATP than anaerobic glycolysis. Cardiac muscle on the other hand, can readily consume any of the three macronutrients (protein, glucose and fat) without a 'warm up' period and always extracts the maximum ATP yield from any molecule involved. The heart and liver will also consume lactic acid produced and excreted by skeletal muscles during exercise.


Nervous control

Efferent leg
The efferent leg of the peripheral nervous system is responsible for conveying commands to the muscles and glands, and is ultimately responsible for voluntary movement. Nerves move muscles in response to voluntary and autonomic (involuntary) signals from the brain. Deep muscles, superficial muscles, muscles of the face and internal muscles all correspond with dedicated regions in the primary motor cortex of the brain, directly anterior to the central sulcus that divides the frontal and parietal lobes.

In addition, muscles react to reflexive nerve stimuli that do not always send signals all the way to the brain. In this case, the signal from the afferent fiber does not reach the brain, but produces the reflexive movement by direct connections with the efferent nerves in the spine. However, the majority of muscle activity is volitional, and the result of complex interactions between various areas of the brain.

Nerves that control skeletal muscles in mammals correspond with neuron groups along the primary motor cortex of the brain's cerebral cortex. Commands are routed though the basal ganglia and are modified by input from the cerebellum before being relayed through the pyramidal tract to the spinal cord and from there to the motor end plate at the muscles. Along the way, feedback loops such as that of the extrapyramidal system contribute signals to influence muscle tone and response.

Deeper muscles such as those involved in posture often are controlled from nuclei in the brain stem and basal ganglia.


Afferent leg
The afferent leg of the peripheral nervous system is responsible for conveying sensory information to the brain, primarily from the sense organs like the skin. In the muscles, the muscle spindles convey information about the degree of muscle length and stretch to the central nervous system to assist in maintaining posture and joint position. The sense of where our bodies are in space is called proprioception, the perception of body awareness. More easily demonstrated than explained, proprioception is the "unconscious" awareness of where the various regions of the body are located at any one time. This can be demonstrated by anyone closing their eyes and waving their hand around. Assuming proper proprioceptive function, at no time will the person lose awareness of where the hand actually is, even though it is not being detected by any of the other senses.

Several areas in the brain coordinate movement and position with the feedback information gained from proprioception. The cerebellum and red nucleus in particular continuously sample position against movement and make minor corrections to assure smooth motion.


Role in health and disease

Exercise
Exercise is often recommended as a means of improving motor skills, fitness, muscle and bone strength, and joint function. Exercise has several effects upon muscles, connective tissue, bone, and the nerves that stimulate the muscles.

Various exercises require a predominance of certain muscle fiber utilization over another. Aerobic exercise involves long, low levels of exertion in which the muscles are used at well below their maximal contraction strength for long periods of time (the most classic example being the marathon). Aerobic events, which rely primarily on the aerobic (with oxygen) system, use a higher percentage of Type I (or slow-twitch) muscle fibers, consume a mixture of fat, protein and carbohydrates for energy, consume large amounts of oxygen and produce little lactic acid. Anaerobic exercise involves short bursts of higher intensity contractions at a much greater percentage of their maximum contraction strength. Examples of anaerobic exercise include sprinting and weight lifting. The anaerobic energy delivery system uses predominantly Type II or fast-twitch muscle fibers, relies mainly on ATP or glucose for fuel, consumes relatively little oxygen, protein and fat, produces large amounts of lactic acid and can not be sustained for as long a period as aerobic exercise. The presence of lactic acid has an inhibitory effect on ATP generation within the muscle though not producing fatigue, it can inhibit or even stop performance if the intracellular concentration becomes too high. However, long-term training causes neovascularization within the muscle, increasing the ability to move waste products out of the muscles and maintain contraction. Once moved out of muscles with high concentrations within the sarcomere, lactic acid can be used by other muscles or body tissues as a source of energy. The ability of the body to export lactic acid and use it as a source of energy depends on training level.

Humans are genetically predisposed with a larger percentage of one type of muscle group over another. An individual born with a greater percentage of Type I muscle fibers would theoretically be more suited to endurance events, such as triathlons, distance running, and long cycling events, whereas a human born with a greater percentage of Type II muscle fibers would be more likely to excel at anaerobic events such as a 200 meter dash, or weightlifting. People with high overall musculation and balanced muscle type percentage engage in sports such as rugby or boxing and often engage in other sports to increase their performance in the former.[citations needed]

Delayed onset muscle soreness is pain or discomfort that may be felt one to three days after exercising and subsides generally within two to three days later. Once thought to be caused by lactic acid buildup, a more recent theory is that it is caused by tiny tears in the muscle fibres caused by eccentric contraction, or unaccustomed training levels. Since lactic acid disperses fairly rapidly, it could not explain pain experienced days after exercise.[5]


Disease
Main article: Neuromuscular disease
Symptoms of muscle diseases may include weakness, spasticity, myoclonus and myalgia. Diagnostic procedures that may reveal muscular disorders include testing creatine kinase levels in the blood and electromyography (measuring electrical activity in muscles). In some cases, muscle biopsy may be done to identify a myopathy, as well as genetic testing to identify DNA abnormalities associated with specific myopathies and dystrophies.

Neuromuscular diseases are those that affect the muscles and/or their nervous control. In general, problems with nervous control can cause spasticity or paralysis, depending on the location and nature of the problem. A large proportion of neurological disorders leads to problems with movement, ranging from cerebrovascular accident (stroke) and Parkinson's disease to Creutzfeldt-Jakob disease.

A non-invasive elastography technique that measures muscle noise is undergoing experimentation to provide a way of monitoring neuromuscular disease. The sound produced by a muscle comes from the shortening of actomyosin filaments along the axis of the muscle. During contraction, the muscle shortens along its longitudinal axis and expands across the transverse axis, producing vibrations at the surface.[6]


Atrophy
There are many diseases and conditions which cause a decrease in muscle mass, known as muscle atrophy. Example include cancer and AIDS, which induce a body wasting syndrome called cachexia. Other syndromes or conditions which can induce skeletal muscle atrophy are congestive heart disease and some diseases of the liver.

During aging, there is a gradual decrease in the ability to maintain skeletal muscle function and mass, known as sarcopenia. The exact cause of sarcopenia is unknown, but it may be due to a combination of the gradual failure in the "satellite cells" which help to regenerate skeletal muscle fibers, and a decrease in sensitivity to or the availability of critical secreted growth factors which are necessary to maintain muscle mass and satellite cell survival. Sarcopenia is a normal aspect of aging, and is not actually a disease state.


Strength
A display of "strength" (e.g lifting a weight) is a result of three factors that overlap; Physiological strength (muscle size, cross sectional area, available crossbridging, responses to training), neurological strength (how strong or weak is the signal that tells the muscle to contract), and mechanical strength (muscle's force angle on the lever, moment arm length, joint capabilities).


The 'strongest' human muscle
Since three factors affect muscular strength simultaneously and muscles never work individually, it is unrealistic to compare strength in individual muscles, and state that one is the "strongest". Accordingly, no one muscle can be named 'the strongest', but below are several muscles whose strength is noteworthy for different reasons.

In ordinary parlance, muscular "strength" usually refers to the ability to exert a force on an external object—for example, lifting a weight. By this definition, the masseter or jaw muscle is the strongest. The 1992 Guinness Book of Records records the achievement of a bite strength of 4337 N (975 lbf) for 2 seconds. What distinguishes the masseter is not anything special about the muscle itself, but its advantage in working against a much shorter lever arm than other muscles. 
If "strength" refers to the force exerted by the muscle itself, e.g., on the place where it inserts into a bone, then the strongest muscles are those with the largest cross-sectional area. This is because the tension exerted by an individual skeletal muscle fiber does not vary much. Each fiber can exert a force on the order of 0.3 micronewton. By this definition, the strongest muscle of the body is usually said to be the quadriceps femoris or the gluteus maximus. 
A shorter muscle will be stronger "pound for pound" (i.e., by weight) than a longer muscle. The myometrial layer of the uterus may be the strongest muscle by weight in the human body. At the time when an infant is delivered, the entire human uterus weighs about 1.1 kg (40 oz). During childbirth, the uterus exerts 100 to 400 N (25 to 100 lbf) of downward force with each contraction. 
The external muscles of the eye are conspicuously large and strong in relation to the small size and weight of the eyeball. It is frequently said that they are "the strongest muscles for the job they have to do" and are sometimes claimed to be "100 times stronger than they need to be." However, eye movements (particularly saccades used on facial scanning and reading) do require high speed movements, and eye muscles are 'exercised' nightly during Rapid eye movement. 
The unexplained statement that "the tongue is the strongest muscle in the body" appears frequently in lists of surprising facts, but it is difficult to find any definition of "strength" that would make this statement true. Note that the tongue consists of sixteen muscles, not one. 
The heart has a claim to being the muscle that performs the largest quantity of physical work in the course of a lifetime. Estimates of the power output of the human heart range from 1 to 5 watts. This is much less than the maximum power output of other muscles; for example, the quadriceps can produce over 100 watts, but only for a few minutes. The heart does its work continuously over an entire lifetime without pause, and thus does "outwork" other muscles. An output of one watt continuously for seventy years yields a total work output of two to three gigajoules. 

Efficiency
The efficiency of human muscle has been measured (in the context of rowing and cycling) at 14% to 27%. The efficiency is defined as the ratio of mechanical work output to the total metabolic cost.


Muscle evolution
Evolutionarily, specialized forms of skeletal and cardiac muscles predated the divergence of the vertebrate/arthropod evolutionary line.[7] This indicates that these types of muscle developed in a common ancestor sometime before 700 million years ago (mya). Vertebrate smooth muscle (smooth muscle found in humans) was found to have evolved independently from the skeletal and cardiac muscles.


References
Costill, David L and Wilmore, Jack H. (2004). Physiology of Sport and Exercise. Champaign, Illinois: Human Kinetics. ISBN 0-7360-4489-2. 
Phylogenetic Relationship of Muscle Tissues Deduced from Superimposition of Gene Trees, Satoshi OOta and Naruya Saitou, Mol. Biol. Evol. 16(6) 856-7, 1999 
Johnson George B. (2005) "Biology, Visualizing Life." Holt, Rinehart, and Winston. ISBN 0-03-016723-X 

Notes
^ Definition and origin of the word 'muscle' 
^ KMLE Medical Dictionary. KMLE Medical Dictionary Definition of muscle. Retrieved on 17 Feb 2006. 
^ Larsson, L; Edstrom L, Lindegren B, Gorza L, Schiaffino S (July 1991). "MHC composition and enzyme-histochemical and physiological properties of a novel fast-twitch motor unit type". The American Journal of Physiology 261 (1 pt 1): C93–101. PMID 1858863. Retrieved on 11 June 2006.  
^ Smerdu, V; Karsch-Mizrachi I, Campione M, Leinwand L, Schiaffino S (December 1994). "Type IIx myosin heavy chain transcripts are expressed in type IIb fibers of human skeletal muscle". The American Journal of Physiology 267 (6 pt 1): C1723–1728. PMID 7545970. Retrieved on 11 June 2006.  Note: Access to full text requires subscription; abstract freely available 
^ Robergs R, Ghiasvand F, Parker D (2004). "Biochemistry of exercise-induced metabolic acidosis.". Am J Physiol Regul Integr Comp Physiol 287 (3): R502-16. PMID 15308499.  
^ 'Muscle noise' could reveal diseases' progression 18 May 2007, NewScientist.com news service, Belle Dumé 
^ Evolution of muscle fibers 

See also
Look up Muscle in
Wiktionary, the free dictionary.Wikimedia Commons has media related to: 
musclesFascia 
Bodybuilding 
List of muscles of the human body 
Myopathy (Pathology of muscle cells) 
Myotomy 
Rapid plant movement 
Atrophy 
Muscle atrophy 
Muscle tone (residual muscle tension) 
Electroactive polymers (materials that behave like muscles, used in robotics research) 
Muscle memory 
Musculoskeletal system 

External links
Physics factbook (Heart output 1.3 to 5 watts, lifetime output 2 to 3 ×109 joules) 
University of Dundee article on performing neurological examinations (Quadriceps "strongest") 
Muscle efficiency in rowing 
Human Muscle 
Quiz 
Muscular System
1. A sarcomere
is a section of a myofibril.
gets shorter when it contracts.
has striations.
All of the choices are correct.

2. During muscular contraction
actin and myosin filaments slide past each other.
ATP supplies energy. 
calcium ions (Ca++) are involved.
all of the above


3. At a neuromuscular junction, 
a nerve impulse causes the release of a neurotransmitter.
a neurotransmitter causes calcium to be released into the muscle cell. 
A & B
none of the above


4. Which is NOT a function of muscles?
cause movement
produce heat
absorb nutrients
maintain posture


5. A skeletal muscle cell
has light and dark bands (striations).
has only one nucleus.
is under involuntary control.
None of the above are true


6. The origin of the biceps brachii is 
the attachment of the muscle that remains relatively fixed during contraction. 
the scapula.
proximal radius.
A & B


7. The stages in muscle contraction include a
nerve impulse reaching a neuromuscular junction.
nerve impulse stimulating the release of calcium ions.
actin filaments sliding past myosin filaments. 
all the above are true


8. The functional unit of a muscle fiber is the 
sarcomere.
myofilament.
myofibril.
neuromuscular junction.


9. Which of the following statements is NOT true about muscle activity. 
Muscles can only pull, they never push.
All muscles have at least two attachments: the origin and insertion.
During contraction, the muscle origin moves toward the insertion.
All muscles cross at least one joint.


10. Muscle fatigue is due, in part, to the accumulation of
lactic acid.
citric acid.
ATP.
ACTH.

http://lrn.org/Content/Quizzes/Qmuscle.html
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5125488918058806226"><img src="http://lh5.google.com/cardwell.bob/RyFlA9UYq9I/AAAAAAAABzU/XFfxv0ZEpQI/s800/myelinated.gif.jpg" /></a></html>
 Lesson 1
INTRODUCTION

10-1. NEED FOR A CIRCULATORY SYSTEM

In simple organisms such as unicellular and one-or two-layer organisms, materials can be transferred among cells by simple processes of diffusion. However, in large organisms, a system is needed for the distribution and collection of materials. This is because diffusion does not occur fast enough to carry the large volumes of materials necessary through the greater distances required.

10-2. DISTRIBUTION OF SUBSTANCES 

Products of the Digestive System. Some of the substances distributed to the body cells are products of the digestive system. These materials meet individual cell requirements for energy, growth, repair, synthesis of new materials, and storage for later use. 
Oxygen. In the lungs, oxygen is obtained by the blood through the process of external respiration. Oxygen is then transported to the individual body cells, where it is used in metabolic oxidation. This provides energy for production of ATP (adenosine triphosphate), which is necessary for carrying on the life processes of the body. 
10-3. COLLECTION OF SUBSTANCES

Some substances are collected from the body cells for elimination. These include carbon dioxide, nitrogenous wastes, and other potentially harmful substances that are carried to organs like the lungs, liver, or kidneys for elimination from the body.

10-4. HORMONES AND OTHER CONTROL SUBSTANCES

Hormones are the products of endocrine glands (see lesson 11). Hormones and other control substances are distributed throughout the body by circulatory systems. The tissues or organs affected by these substances are usually called target organs. In turn, substances released by the target organs often affect the original endocrine gland. This results in a feedback system.

10-5. CONTINUOUS RENEWAL AND REMOVAL OF FLUIDS

Secretory processes continuously renew the various fluid systems of the human body. At the same time, the volume of fluid in each system is kept at a constant level through the removal of excess fluids. Should the removal processes be interrupted, the volume of fluid will increase. The resulting increase in pressure can have serious consequences. Depending on the system involved, the consequences might include deafness, hydrocephalus, or pulmonary edema.

10-6. COMPONENTS OF ANY CIRCULATORY SYSTEM Any circulatory system has three general components: 

Vehicle. The vehicle is a fluid (flowing) medium. The materials being carried are dissolved or suspended in this fluid. This is the blood, lymph, or cerebrospinal fluid. 
Conduits. Conduits are like pipes. They contain the fluids in which materials are transported to and from the various parts of the body. These are the blood vessels or lymph vessels. 
Motive Forces. Motive forces act upon the vehicle to make it flow through the conduits. These are provided by the heart. 
10-7. EXAMPLES OF CIRCULATORY SYSTEMS

Some circulatory systems of the human body are the cardio-vascular system, the lymphatic system, and the CSF (cerebrospinal fluid) system. The lesser systems include the aqueous humor of the bulbus oculi (eyeball) and the endolymph and perilymph, which are fluids of the inner ear.

10-8. INTRODUCTION TO THE CARDIOVASCULAR SYSTEM

The cardiovascular system (Figure 10-1) is the primary circulatory system of the human body. It includes a heart, blood, and blood vessels. 

One function of the cardiovascular system is transport. Some substances carried by the cardiovascular system are dissolved or suspended in the fluid portion of the blood. Others are bound up in special cellular elements (RBCs). 
The cardiovascular system also provides protection against foreign substances. This function involves active attack by white blood cells as well as more subtle processes of the immune system. 


Figure 10-1. Diagram of the human cardiovascular (cirulatory) system.
 
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NERVOUS SYSTEM 

Nervous systems aid in the regulation and maintenance of homeostasis of an organism 


NEURON - THE BASIC CELL WHICH ALL NERVOUS SYSTEM ARE MADE OF 

  

                                                                drawing by Robert Turner 

Parts and Function of a Neuron 

Cell Body (2)- portion of a neuron most resembling other cell, contains a nucleus and cytoplasm, receives impulses from dendrite 

axon (5)- long part of a neuron leading away from the cell body, transmits impulses away from the cell body 

dendrite (1)- highly branched structures at one end of a neuron, impulses are conducted toward the cell body 

Schwann cell (3)- aid in the nutrition and regeneration of axon 

end brush (4)- filaments forming the end of a axon, release neurotransmitters 

synapse- gap between two neurons receives impulse from one neuron and then sends then to the other neuron by releasing a neurotransmitter 


myelin sheath- fatty outer layer that encloses the axon of many neurons, acts as an insulating layer to keep impulses from jumping to other neurons (shorting out) 

neurolemma- thin membrane covering sounding the myelin sheath 

terminal branch- branching out of the axon 


Impulses are transmitted electrochemically throughout the neuron as an action potential, impulses cross the synapse as a chemical message called a neurotransmitter 

   

All or None Response 

all or none response- nerve impulse either fires or does not fire in a neuron 

Threshold- nerve stimulus must have a certain intensity for an impulse to result 

that is : there must be a certain strength stimulus to cause a response to occur 


Reflex Arc 

Reflex arc- path of an impulse takes during a reflex 

includes 5 parts (in order of occurrence) 

1. receptor (stimulus) 

2. sensory neurons 

3. interneurons 

4. motor neurons 

5. effector (response) 

 

 Drawn by Robert Turner 


3 things necessary for a nervous response: 

1. must be a means of detecting a change in environment (stimulus) 

2. a stimulus is transmitted as an impulse along a network of neurons 

3. an effector, which carries out the necessary response to the stimulus 


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Vertebrate nervous systems 

 The two major portion of a vertebrate nervous system are the central nervous system (CNS), and the peripheral nervous system. The cns consists of a brain and one or more nerve cords. The peripheral nervous system is made up of sensory and motor neurons connected to the cns. It also has nerves that are connected to the cns with receptors, a sense organ and effectors( a muscle or gland). 

Central nervous system 


Brain 


Parts of the brain and their functions 

Fore brain 

Cerebrum - senses, cognitive abilities, memory 

Consists of: 

temporal lobe- learning and memory, senses of taste, smell, and hearing 

parietal lobe- sensory input, touch 

occipital lobe- vision, motor input, speech 

frontal lobe- personality, learning, thought and speech 

midbrain- relay center for impulses traveling to and through the brain 

Consists of : 

Thalmus - directs incoming impulses to the correct part of the cerebrum 

Hypothalmus - produces hormones, controls body activities related to homeostasis 

cerebellum- coordinating impulses posture and balance motor coordination muscle tone 

Hind brain- heart rate, breathing and other internal organ control 

Medulla - regulates heart rate 

Pons - regulates breathing by monitoring the carbon dioxide level of the blood 

meninges- 3 thin layers of fluid filled tissue that cover the brain and spinal cord for protection 

 


Spinal cord 

Functions of the Spinal Cord 

1. controls reflexes 

2. relays messages from the brain to the body and from the body to the brain 


--------------------------------------------------------------------------------

Peripheral Nervous System 

Contains two pathways for nerve impulses to travel 


The afferent pathway consists of nerve cells that convey information from receptors in the periphery of the body to the central nervous system 

The efferent pathway consists of nerve cells that convey information from the central nervous system to muscles on glands. 


And consists of two parts: 

1. Autonomic nervous system- 

carries messages to and from the " automatically functioning" or involuntary muscles and sense organs like the heart, lungs, digestive system, etc. 

The parts of the autonomic nervous system are the parasympathetic system and the sympathetic system. 


Sympathetic system - responds during times of stress 

( increases heart rate, breathing, etc. while slowing digestion etc.) 


Parasympathetic system- returns the body to normal conditions after a period of stress. 


2. Sensory somatic System- 

Carries messages to and from the voluntary muscles and sense organs like skeletal muscles 


--------------------------------------------------------------------------------

The five senses 


1. sight 

The part of the brain that is sight occurs in is occipital lobe. Information is transmitted through bipolar neurons to ganglion cells. The cell bodies of the ganglion cells lie in the retina of the eye and their axons pass through the optic nerve to the occipital lobe. 

 


2. hearing 

Sound was vibrations in the air enter the outer ear, the vibrations are picked up by the middle ear bones and transmitted to the inner ear where the auditory nerves are stimulated and transmit impulses to the temporal lobe. 

  

3. taste 

The surface of the tongue is not smooth, in fact it's sandpapery surface is made by the presence of thousands of tiny papillae, or taste buds. 

 

Their are four kinds of taste buds. Each have a different function. They're arranged in bitter, sweet, salty, and sour. 

Salty and sweet cells are found in the front of the tongue. Sour cells are in the middle, and the bitter cells are found in the back. 

Taste buds are connected to neurons, which transmit messages to the brain. 


These neurons are called sensory neurons, the message are sent to the temporal lobe of the brain. 

4. smell 

Olfactory receptor cells are located in the nasal epithelium within the roof of the nasal cavity on both sides of the nasal septum. 

The free end of each olfactory cell contains several dendrites with olfactory hairs which are the chemically sensitive portion of receptor cell. 

Sensory impulses are conveyed along the olfactory tract and into the olfactory portion of the temporal lobe, where they are interpreted as smell. 


5. touch 

Touch is a general term that includes several related senses such as pain, pressure, heat and cold. Each of these "touch" senses is defected by separate skin receptors. Each kind of receptor detects only one sense. The number of location of touch receptors around the body varies. For example, there are more touch receptors in the finger tips than in the legs. Whether detected by a simple nerve ending or special cells in a complex organ, sensory information causes action potentials in neurons. Each receptor or sense organ sends impulse to particular parts of the brain where they are interpreted and correct responses can be made. 

Disorders of the Nervous System 


Stroke 

Stroke- occurs when the blood supply to a part of the brain tissue is cut off 

Result- the nerve cells in that part of the brain die and thus cannot function 

When this happens the part of the body controlled by these nerve cells can not function either. 

Treatments- steroids (to decrease swelling), physical therapy, ventilators, tube feeding, and Hospice Care (for comfort measures) 

Preventions- No smoking, controlled anxiety, controlled blood pressure, normal weight, low fat and low cholesterol diet to prevent clogging of arteries of the brain 

Meningitis 

Meningitis- inflammation (swelling ) of the meninges 

Causes- a virus or bacterial infection 

Treatments- antibiotics for bacterial infection, but there is no known specific treatment for viral meningitis 

Adrenleukodystrophy ( ALD) 

ALD - occurs when the Myelin sheath around the axons of the nerve cells of the brain degenerate and allow nerve impulses to jump from one neuron to surrounding neurons causing a kind of short circuiting of the brain and its functions resulting in a progressive degeneration of abilities resulting in coma then death if untreated. Usually affects young male children. 


Treatments - diet high in the type of fat needed to maintain the Myelin 


Effects of drugs and Alcohol 



Stimulants 

stimulants-increases activity of the nervous system,works on CNS (central nervous system) 

Examples- Caffeine, cocaine, 

Effects- increases activity of involuntary organs, making the person hyper 

Where and How- increases stimulation of the autonomic nervous system in the brainstem, arousal system and cerebral cortex 

Depressant 

Depressant- "downer" 

Examples- Sleeping pills, Valium, Barbiturates, and certain pain medication 

Effect- depress body function or nerve activity making person dull or less active 

Where and How- works on the thalamus and hypothalamus causing calming effects 

Hallucinogen 

hallucinogen- drugs that effect the way the brain interprets sensory input 

Examples- LSD (lysergic Acid Diethylamide), peyto, and sometimes alcohol 

Effects- produces hallucinations ; maybe visual, auditory, or olfactory 

judgement maybe impaired, can't tell the difference between what is real or imaginary 

Alcohol 

BAC- Blood Alcohol Content 

Effects as BAC levels rise- in general alcohol being a depressant causes your brain to shut off one part at a time, starting with the parts least necessary to maintain life 

low BAC level - Affects the cerebrum by impairing senses and thinking, depresses inhibitions, this definitely affects your ability to drive! 

moderate BAC level - Begins to affect the cerebellum as well, causing slurred speech and staggering, will shut off cerebrum all together causing one to pass out 

high BAC level - Begins by causing vomiting, progresses by shutting off cerebellum functioning and then affects the medulla (brain stem) by causing alcohol induced heart attack or coma. 


Legal intoxication for adults is a BAC of .1 

Legal intoxication for minors is a BAC of .01 

Both levels are consider to be in the low BAC range 



Pain Killers 

Pain Killers- naturally occurring or man made copies of endorphins and enkelphins 

Effects- they stop the pain "message"  impulse from reaching the brain 

Where and How- pain killers act like neurotransmitters and act in the synapses 

Endorphins- effect emotions 

Enkelpahins- also reduce the pain feeling and are known as natural opiates 


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Quiz 
Nervous System
1. Neurons that conduct nerve impulses from the receptors to the central nervous system are
motor neurons.
efferent neurons.
interneurons.
sensory neurons.***

2. Processes that carry nerve impulses away from the cell body are called
dendrites.
axons. ***
synapses.
myelin sheaths.


3. The neuroglia that produce myelin sheaths around axons in the peripheral nervous system are
Schwann cells.***
oligodendrocytes.
microglia.
astroctyes.


4. The portion of the nervous system that is considered involuntary is the 
somatic nervous system.
sensory nervous system.
autonomic nervous system.***
motor nervous system.


5. All of the following are functions of the nervous system EXCEPT
senses changes.
analyzes changes.
stores calcium.***
responses to changes.


6. The different charge between the outside and the inside of a neuron at rest is called
action potential.
synaptic potential.
resting membrane potential.***
equilibrium potential.


7. The stage in an action potential that immediately follows depolarization is
polarization.
repolarization.***
threshold. 
the resting period.


8. The junction between two nerve cells is called
neuromuscular junction.
neuroglandular junction.
gap junction.
synapse.***


9. Neurotransmitters are released at the
dendrite.
axon terminal.***
cell body.
myelin sheath.


10. In the reflex arc, a muscle or gland is considered to be the
receptor.
integrating center.
motor neuron.
effector.***
http://en.wikipedia.org/wiki/Nervous_Tissue

Nervous tissue
From Wikipedia, the free encyclopedia
(Redirected from Nervous Tissue)• Ten things you didn't know about Wikipedia •Jump to: navigation, search
 
Example of nervous tissue.Nervous tissue is the fourth major class of vertebrate tissue. The function of the nervous tissue is in communication between parts of the body. It is composed of neurons, which transmit impulses, and the neuroglia, which assist propagation of the nerve impulse as well as provide nutrients to the neuron.

All nervous tissue of an organism makes up its nervous system, which may include the Brain, Spinal Cord, and nerves throughout the organism.

Nervous tissue is made of nerve cells that come in many varieties, all of which are distinctly characteristic by the axon or long stem like part of the cell that sends action potential signals to the next cell.

All living cells have the ability to react to stimuli. Nervous tissue is specialized to react to stimuli and to conduct impulses to various organs in the body which bring about a response to the stimulus. Nerve tissue (as in the brain, spinal cord and peripheral nerves that branch throughout the body) are all made up of specialized nerve cells called neurons. Neurons are easily stimulated and transmit impulses very rapidly. A nerve is made up of many nerve cell fibers (neurons) bound together by connective tissue. A sheath of dense connective tissue, the epineurium, surrounds the nerve. This sheath penetrates the nerve to form the perineurium which surrounds bundles of nerve fibers. blood vessels of various sizes can be seen in the epineurium. The endoneurium, which consists of a thin layer of loose connective tissue, surrounds the individual nerve fibers.

Contents [hide]
1 Organizational Structure 
2 Structure of a Motor Neuron 
2.1 A motor neuron 
2.2 A Synapse 
3 Classification of Neurons 
4 Functions of Nerve Tissue 
5 External links 
 


[edit] Organizational Structure
Although the system forms a unit it can be divided into the following parts: the central nervous system (CNS) which consists of the brain and spinal cord, and the peripheral nervous system (PNS) consists of the nerves outside the CNS which connect the brain and spinal cord to the organs and muscles of the body.[1]

There are three main types of neurons, which are classified according their function:

Those that conduct impulses from the sensory organs to the central nervous system (brain and spinal cord) are called sensory (or afferent) neurons. 
Those that conduct impulses from the central nervous system to the effector organs (such as muscles and glands) are called motor (or efferent) neurons. 
Those that connect sensory neurons to motor neurons are called interneurons (also known as connector neurons or association neurons) 

[edit] Structure of a Motor Neuron
A motor neuron has many processes (cytoplasmic extensions), called dendrites, which enter a large, grey cell body at one end. A single process, the axon, leaves at the other end, extending towards the dendrites of the next neuron or to form a motor endplate in a muscle. Dendrites are usually short and divided while the axons are very long and does not branched freely. The impulses are transmitted through the motor neuron in one direction, i.e. into the cell body by the dendrites and away from the cell body by the axon . The cell body is enclosed by a cell (plasma) membrane and has a central nucleus. Granules called Nissl bodies are found in the cytoplasm of the cell body. Within the cell body, extremely fine neurofibrils extend from the dendrites into the axon. The axon is surrounded by the myelin sheath, which forms a whitish, non-cellular, fatty layer around the axon. Outside the myelin sheath is a cellular layer called the neurilemma or sheath of Schwann cells. The myelin sheath together with the neurilemma is also known as the medullary sheath. This medullary sheath is interrupted at intervals by the nodes of Ranvier.





[edit] A motor neuron
Nerve cells are functionally connected to each other at a junction known as a synapse, where the terminal branches of an axon and the dendrites of another neuron lie in close proximity to each other but never make direct contact.





[edit] A Synapse

[edit] Classification of Neurons
On the basis of their structure, neurons can also be classified into three main types:

Unipolar Neurons 
Sensory neurons have only a single process or fibre which divides close to the cell body into two main branches (axon and dendrite). Because of their structure they are often referred to as unipolar neurons. 
Multipolar Neurons 
Motor neurons, which have numerous cell processes (an axon and many dendrites) are often referred to as multipolar neurons. Interneurons are also multipolar. 
Bipolar Neurons 
Bipolar neurons are spindle-shaped, with a dendrite at one end and an axon at the other . An example can be found in the light-sensitive retina of the eye. 

[edit] Functions of Nerve Tissue
Nervous tissue allows an organism to sense stimuli in both the internal and external environment. The stimuli are analysed and integrated to provide appropriate, co-ordinated responses in various organs.

The afferent or sensory neurons conduct nerve impulses from the sense organs and receptors to the central nervous system. 
Internuncial or connector neurons supply the connection between the afferent and efferent neurons as well as different parts of the central nervous system. 
Efferent or somatic motor neurons transmit the impulse from the central nervous system to a muscle (the effector organ) which then react to the initial stimulus. 
Autonomic motor or efferent neurons transmit impulses to the involuntary muscles and glands. 

[edit] External links
Histology at uwa.edu.au 
Histology at usc.edu 
  This neuroscience article is a stub. You can help Wikipedia by expanding it. 

  This cell biology article is a stub. You can help Wikipedia by expanding it. 

[show]v • d • eBiological tissue 
Animals Epithelium - Connective - Muscular - Nervous 
Plants Dermal - Vascular - Ground 
[show]v • d • eHistology: nervous tissue 
Nervous tissue is found in the brain, spinal cord, and nerves. It is responsible for coordinating and controlling many body activities. It stimulates muscle contraction, creates an awareness of the environment, and plays a major role in emotions, memory, and reasoning. To do all these things, cells in nervous tissue need to be able to communicate with each other by way of electrical nerve impulses. 

The cells in nervous tissue that generate and conduct impulses are called neurons or nerve cells. These cells have three principal parts: the dendrites, the cell body, and one axon. The main part of the cell, the part that carries on the general functions, is the cell body. Dendrites are extensions, or processes, of the cytoplasm that carry impulses to the cell body. An extension or process called an axon carries impulses away from the cell body. 
Nervous Tissue: Structure and Function

Supportive connective tissue cells 

Neuroglia support and protect neurons in the CNS. Specific glial cells are phagocytes; others myelinate neuron processes in the CNS or line cavities. 

Schwann cells myelinate neuron processes in the PNS (Figure 7.2). 

Neurons 

Anatomy: All neurons have a cell body containing the nucleus and processes (fibers) of two types; (1) axons (one per cell) typically generate and conduct impulses away from the cell body and release a neurotransmilter, and (2) dendrites (one to many per cell) typically carry electrical currents toward the cell body. Most large fibers are myelinated; myelin increases the rate of nerve impulse transmission. 

Classification 

On the basis of function (direction of impulse transmission) there are sensory (afferent) and motor (efferent) neurons and association neurons (interneurons). Dendritic endings of sensory neurons are bare (pain receptors), or are associated with sensory receptors (Figure 7.3). 

On the basis of structure, there are unipolar, bipolar, and multipolar neurons; the terminology reveals the number of processes extending from the cell body. Motor and association neurons are multipolar; most sensory neurons are unipolar. The exceptions are sensory neurons in certain special sense organs (ear, eye), which are bipolar. 

Physiology 

A nerve impulse is an electrochemical event (initiated by various stimuli) that causes a change in neuron plasma membrane permeability, allowing sodium ions (Na+) to enter the cell (depolarization). Once begun, the action potential, or nerve impulse, continues over the entire surface of the cell. Electrical conditions of the resting state are restored by the diffusion of potassium ions (K+) out of the cell (repolarization). Ion concentrations of the resting state are restored by the sodium-potassium pump (Figure 7.4). 

A neuron influences other neurons or effector cells by releasing neurotransmitters, chemicals that diffuse across the synaptic cleft and attach to membrane receptors on the postsynaptic cell. The result is opening of specific ion channels and activation or inhibition, depending on the neurotransmitter released and the target cell (Figure 7.5). 

A reflex is a rapid, predictable response to a stimulus. There are two types: autonomic and somatic. The minimum number of components of a reflex arc is four: receptor, effector, and sensory and motor neurons (most, however, have one or more interneurons) (Figure 7.6). Normal reflexes indicate normal nervous system function. 
Nervous system

From Wikipedia, the free encyclopedia


The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. Prominent parts of a nervous system include neurons and nerves, which are used in coordination. All parts of the nervous system are made of nervous tissue. The classification of the nervous system is mostly similar in humans as in other vertebrates.

Contents


    * 1 Humans
          o 1.1 Central nervous system
          o 1.2 Peripheral nervous system
                + 1.2.1 By direction
                + 1.2.2 By function
    * 2 Vertebrates
    * 3 Worms
    * 4 Arthropoda
    * 5 See also
    * 6 External links

 Humans

The nervous system of humans is often divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord.

Central nervous system

    Main article: Central nervous system
    See also: List of regions in the human brain

The central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. Together with the peripheral nervous system, it has a fundamental role in the control of behavior. The CNS is contained within the dorsal cavity, with the brain within the cranial subcavity, and the spinal cord in the spinal cavity. The CNS is covered by the meninges. The brain is also protected by the skull, and the spinal cord is also protected by the vertebrae.

Central
nervous
system 	Brain 	Prosencephalon 	Telencephalon 	

Rhinencephalon, Amygdala, Hippocampus, Neocortex, Lateral ventricles
Diencephalon 	

Epithalamus, Thalamus, Hypothalamus, Subthalamus, Pituitary gland, Pineal gland, Third ventricle
Brain stem 	Mesencephalon 	

Tectum, Cerebral peduncle, Pretectum, Mesencephalic duct
Rhombencephalon 	Metencephalon 	

Pons, Cerebellum,
Myelencephalon 	Medulla oblongata
Spinal cord

[edit] Peripheral nervous system

    Main article: Peripheral nervous system

The PNS consists of all other nerves and neurons that do not lie within the CNS. The large majority of what are commonly called nerves (which are actually axonal processes of nerve cells) are considered to be PNS. The peripheral nervous system can be further classified either by direction of neurons and by function.

 By direction

There are three types of directions of the neurones:

    * Sensory system by sensory neurons, which carry impulses from a receptor to the CNS
    * Efferent system by motor neurons, which carry impulses from the CNS to an effector
    * Relay system by relay neurons (also called interneurons), which transmit impulses between the sensory and motor neurones. However, there are relay neurons in the CNS as well.

The junction between two neurones is called a synapse. There is a very narrow gap between the neurones - the synaptic cleft.

[edit] By function

By function, the peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.

The somatic nervous system is responsible for coordinating the body's movements, and also for receiving external stimuli. It is the system that regulates activities that are under conscious control.

The autonomic nervous system is then split into the sympathetic division, parasympathetic division, and enteric division. The sympathetic nervous system responds to impending danger or stress, and is responsible for the increase of one's heartbeat and blood pressure, among other physiological changes, along with the sense of excitement one feels due to the increase of adrenaline in the system. The parasympathetic nervous system, on the other hand, is evident when a person is resting and feels relaxed, and is responsible for such things as the constriction of the pupil, the slowing of the heart, the dilation of the blood vessels, and the stimulation of the digestive and genitourinary systems. The role of the enteric nervous system is to manage every aspect of digestion, from the esophagus to the stomach, small intestine and colon.
Peripheral
nervous
system 	by direction 	sensory system
efferent system
By function 	Somatic
Autonomic 	Sympathetic
Parasympathetic
Enteric

[edit] Vertebrates

The nervous system of all vertebrate animals, is often divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord.

[edit] Worms

Planaria, a type of flatworm, have dual nerve cords running along the length of the body and merging at the tail and the mouth. These nerve cords are connected by transverse nerves like the rungs of a ladder. These transverse nerves help coordinate the two sides of the animal. Two large ganglia at the head end function similar to a simple brain. Photoreceptors on the animal's eyespots provide sensory information on light and dark.

The nervous system of the roundworm Caenorhabditis elegans has been mapped out to the cellular level. Every neuron and its cellular lineage has been recorded and most, if not all, of the neural connections are known. In this species, the nervous system is sexually dimorphic; the nervous systems of the two sexes, males and hermaphrodites, have different numbers of neurons and groups of neurons that perform sex-specific functions. In C. elegans, males have exactly 383 neurons, while hermaphrodites have exactly 302 neurons [1]

[edit] Arthropoda

Arthropods, such as insects and crustaceans, have a nervous system made up of a series of ganglia, connected by a ventral nerve cord made up of two parallel connectives running along the length of the belly [2]. Typically, each body segment has one ganglion on each side, though some ganglia are fused to form the brain and other large ganglia [3].

The head segment contains the brain, also known as the supraesophageal ganglion. In the insect nervous system, the brain is anatomically divided into the protocerebrum, deutocerebrum, and tritocerebrum. Immediately behind the brain is the subesophageal ganglion, which is composed of three pairs of fused ganglia. It controls the mouthparts, the salivary glands and certain muscles.

Many arthropods have well-developed sensory organs, including compound eyes for vision and antennae for olfaction and pheromone sensation. The sensory information from these organs is processed by the brain.

[edit] See also

    * Major systems of the human body
    * Neural tissue
    * Neural network
    * Neuroendocrinology
    * Neuroscience
    * Neurotoxin
    * Neural ensemble
    * Somatic sensation
A pathway of the human nervous system is the series of neurons or other structures used to transmit an item of information. In general, we consider two major types of pathways-the general sensory pathways and the motor pathways.
Neuroglia cells do not conduct nerve impulses, but instead, they support, nourish, and protect the neurons. They are far more numerous than neurons and, unlike neurons, are capable of mitosis.
Neurons, or nerve cells, carry out the functions of the nervous system by conducting nerve impulses. They are highly specialized and amitotic. This means that if a neuron is destroyed, it cannot be replaced because neurons do not go through mitosis. The image below illustrates the structure of a typical neuron.
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5125488892289002290"><img src="http://lh3.google.com/cardwell.bob/RyFk_dUYqzI/AAAAAAAAByE/nIM76WUcKZ8/s800/synapse.gif.jpg" /></a></html>
Lesson 2
OTHER PARTS OF THE HUMAN URINARY SYSTEM

8-5. THE URETERS

The ureter is a tubular structure that is continuous with the renal pelvis. The ureter of each kidney passes down the posterior abdominal wall on its respective side.

The ureter then enters the pelvic region. The urine moves along the ureters drop by drop, pushed by the wave like muscular contractions (peristalsis) of the tubular wall. In the pelvis, the two ureters enter the posterior inferior corners of the urinary bladder.

8-6. THE URINARY BLADDER

The urinary bladder is an organ that is highly specialized to store urine until it is eliminated from the body. 

Trigone. The base of the urinary bladder is known as the trigone because of its triangular shape. The trigone is fairly solid and nonstretchable. 
Stretchable Wall. The rest of the wall of the urinary bladder is very stretchable and forms a spherical sac when filled. 
Transitional Epithelial Lining. The mucosal lining of the urinary bladder is made up of a unique epithelium, called the transitional epithelium. 
(1)  Voiding reflex. The transitional epithelium has the capacity to stretch to a certain degree. At the limit of its stretchability, it causes a message to be sent to the spinal cord about the fullness of the urinary bladder. This initiates the voiding reflex, which would cause the urine to pass out of the body. 
(2)  Increments of stretching and reorganization. Often, however, it is not convenient to void (empty the bladder). Thus, after a short period, the transitional epithelium can reorganize itself and undergo another increment of stretching. Soon, however, the fullness message is somewhat more urgent. There can be several increments of stretching until the limit of the urinary bladder is finally reached. At that limit, the urine must be voided. 
8-7. THE URETHRA

The urethra is the single tubular structure that connects the urinary bladder to the outside. 

Sexual Dimorphism. Relatively short and straight, the female urethra opens directly to the outside. However, the male urethra is incorporated into the penis. Since the male urethra has two more-or-less right-angle turns, one permanent and one flexible, the male is more difficult to catheterize than the female. 
Urethral Sphincters. The urethral sphincters are two muscular structures which prevent urine from leaving the urinary bladder. Each urethral sphincter is a circular mass of muscle tissue. Relaxation of the sphincters allows urine to be forced through them. 
Chapter 22: The Lymphatic System and Immunity  
   
 Objectives 
   
 After successfully completing this chapter, you will be able to:

Explain the difference between nonspecific and specific defense, and the role of lymphocytes in the immune response. 
Identify the major components of the lymphatic system and explain their functions. 
Discuss the importance of lymphocytes and describe their distribution in the body. 
Describe the structure of lymphoid tissues and organs and explain their functions. 
List the body’s nonspecific defenses and explain the function of each. 
Describe the components and mechanisms of each nonspecific defense. 
Define specific resistance and identify the forms and properties of immunity. 
Distinguish between cell-mediated (cellular) immunity and antibody-mediated (humoral) immunity and identify the cells responsible for each. 
Discuss the types of T cells and the role played by each in the immune response. 
Describe the mechanisms of T cell activation and the differentiation of the major classes of T cells. 
Describe the mechanisms of B cell activation and the differentiation of plasma cells and memory B cells. 
Describe the structure of an antibody and discuss the types of antibodies in body fluids and secretions. 
Explain the functions of antibodies and how they perform those functions. 
Discuss the primary and secondary responses to antigen exposure. 
Describe the origin, development, activation, and regulation of normal resistance to disease. 
Explain the origin of autoimmune disorders, immunodeficiency diseases, and allergies and list important examples of each typeof disorder. 
Discuss the effects of stress on the immune function. 
Describe the effects of aging on the lymphatic system and the immune response. 
   




Copyright © 1995-2008 by Benjamin Cummings A division of Pearson Education Legal Disclaimer 


 
Organization of the Nervous System

Structural: All nervous system structures are classified as part of the CNS (brain and spinal cord) or PNS (nerves and ganglia). 

Functional: Motor nerves of the PNS are classified on the basis of whether they stimulate skeletal muscle (somatic division) or smooth/cardiac muscle and glands (autonomic division)
Osteoblast 

An osteoblast (from the Greek words for "bone" and "germ" or embryonic) is a mononucleate cell that is responsible for bone formation. Osteoblasts produce osteoid, which is composed mainly of Type I collagen. Osteoblasts are also responsible for mineralization of the osteoid matrix. Bone is a dynamic tissue that is constantly being reshaped by osteoblasts, which build bone, and osteoclasts, which resorb bone.
http://en.wikipedia.org/wiki/Oxidation

Redox
From Wikipedia, the free encyclopedia
(Redirected from Oxidation)• Ten things you didn't know about Wikipedia •Jump to: navigation, search
“Reduced” redirects here. For other uses, see reduction.
 
Illustration of a redox reactionRedox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed.

This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide, or the reduction of carbon by hydrogen to yield methane (CH4), or it can be a complex process such as the oxidation of sugar in the human body through a series of very complex electron transfer processes.

The term redox comes from the two concepts of reduction and oxidation. It can be explained in simple terms:

Oxidation describes the loss of electrons by a molecule, atom or ion 
Reduction describes the gain of electrons by a molecule, atom or ion 
However, these descriptions (though sufficient for many purposes) are not truly correct. Oxidation and reduction properly refer to a change in oxidation number — the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. In practice, the transfer of electrons will always cause a change in oxidation number, but there are many reactions which are classed as "redox" even though no electron transfer occurs (such as those involving covalent bonds).

Non-redox reactions, which do not involve changes in formal charge, are known as metathesis reactions.

 
The two parts of a redox reaction 
Rusting iron 
A bonfire. Combustion consists of redox reactions involving free radicals.Contents [hide]
1 Oxidizing and reducing agents 
2 Oxidation in industry 
3 Examples of redox reactions 
3.1 Other examples 
4 Redox reactions in biology 
5 Redox cycling 
6 References 
7 See also 
8 External links 
 


[edit] Oxidizing and reducing agents
Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. Put in another way, the oxidant removes electrons from another substance, and is thus reduced itself. And because it "accepts" electrons it is also called an electron acceptor.

Oxidants are usually chemical substances with elements in high oxidation numbers (e.g., H2O2, MnO4−, CrO3, Cr2O72−, OsO4) or highly electronegative substances that can gain one or two extra electrons by oxidizing a substance (O, F, Cl, Br).

Substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. Put in another way, the reductant transfers electrons to another substance, and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor. Reductants in chemistry are very diverse. Metal reduction - electropositive elemental metals can be used (Li, Na, Mg, Fe, Zn, Al). These metals donate or give away electrons readily. Other kinds of reductants are hydride transfer reagents (NaBH4, LiAlH4), these reagents are widely used in organic chemistry[1][2], primarily in the reduction of carbonyl compounds to alcohols. Another useful method is reductions involving hydrogen gas (H2) with a palladium, platinum, or nickel catalyst. These catalytic reductions are primarily used in the reduction of carbon-carbon double or triple bonds.

The chemical way to look at redox processes is that the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or reducing agent loses electrons and is oxidized and the oxidant or oxidizing agent gains electrons and is reduced. The pair of an oxidising and reducing agent that are involved in a particular reaction is called a redox pair.


[edit] Oxidation in industry
Oxidation is used in a wide variety of industries such as in the production of cleaning products.

Redox reactions are the foundation of electrochemical cells.


[edit] Examples of redox reactions
A good example is the reaction between hydrogen and fluorine:

 
We can write this overall reaction as two half-reactions: the oxidation reaction

 
and the reduction reaction:

 
Analysing each half-reaction in isolation can often make the overall chemical process clearer. Because there is no net change in charge during a redox reaction, the number of electrons in excess in the oxidation reaction must equal the number consumed by the reduction reaction (as shown above).

Elements, even in molecular form, always have an oxidation number of zero. In the first half reaction, hydrogen is oxidized from an oxidation number of zero to an oxidation number of +1. In the second half reaction, fluorine is reduced from an oxidation number of zero to an oxidation number of −1.

When adding the reactions together the electrons cancel:

 
And the ions combine to form hydrogen fluoride:

 

[edit] Other examples
iron(II) oxidizes to iron(III): 
Fe2+ → Fe3+ + e− 
hydrogen peroxide reduces to hydroxide in the presence of an acid: 
H2O2 + 2 e− → 2 OH− 
overall equation for the above:

2Fe2+ + H2O2 + 2H+ → 2Fe3+ + 2H2O 
denitrification, nitrate reduces to nitrogen in the presence of an acid: 
2NO3− + 10e− + 12 H+ → N2 + 6H2O 
iron oxidizes to iron(III) oxide and oxygen is reduced forming iron(III) oxide (commonly known as rusting, which is similar to tarnishing): 
4Fe + 3O2 → 2 Fe2O3 
Combustion of hydrocarbons, e.g. in an internal combustion engine, produces water, carbon dioxide, some partially oxidized forms such as carbon monoxide and heat energy. Complete oxidation of materials containing carbon produces carbon dioxide. 
In organic chemistry, stepwise oxidation of a hydrocarbon produces water and, successively, an alcohol, an aldehyde or a ketone, carboxylic acid, and then a peroxide. 
In biology many important processes involve redox reactions. Cell respiration, for instance, is the oxidation of glucose (C6H12O6) to CO2 and the reduction of oxygen to water. The summary equation for cell respiration is: 
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O 
The process of cell respiration also depends heavily on the reduction of NAD+ to NADH and the reverse reaction (the oxidation of NADH to NAD+). Photosynthesis is essentially the reverse of the redox reaction in cell respiration: 
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 

[edit] Redox reactions in biology
 
 
Top: ascorbic acid (reduced form of Vitamin C)
Bottom: dehydroascorbic acid (oxidized form of Vitamin C)Much biological energy is stored and released by means of redox reactions. Photosynthesis involves the reduction of carbon dioxide into sugars and the oxidation of water into molecular oxygen. The reverse reaction, respiration, oxidizes sugars to produce carbon dioxide and water. As intermediate steps, the reduced carbon compounds are used to reduce nicotinamide adenine dinucleotide (NAD+), which then contributes to the creation of a proton gradient, which drives the synthesis of adenosine triphosphate (ATP) and is maintained by the reduction of oxygen. In animal cells, mitochondria perform similar functions. See Membrane potential article.

The term redox state is often used to describe the balance of NAD+/NADH and NADP+/NADPH in a biological system such as a cell or organ. The redox state is reflected in the balance of several sets of metabolites (e.g., lactate and pyruvate, beta-hydroxybutyrate and acetoacetate) whose interconversion is dependent on these ratios. An abnormal redox state can develop in a variety of deleterious situations, such as hypoxia, shock, and sepsis. Redox signaling involves the control of cellular processes by redox processes.


[edit] Redox cycling
A wide variety of aromatic compounds are enzymatically reduced to form free radicals that contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes and their coenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide and regenerate the unchanged parent compound. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen to form superoxide. This catalytic behavior has been described as futile cycle or redox cycling.

Examples of redox cycling-inducing molecules are the herbicide paraquat and other viologens and quinones such as menadione. [1]PDF (2.76 MiB)


[edit] References
^ Hudlický, Miloš (1996). Reductions in Organic Chemistry. Washington, D.C.: American Chemical Society, 429. ISBN 0-8412-3344-6.  
^ Hudlický, Miloš (1990). Oxidations in Organic Chemistry. Washington, D.C.: American Chemical Society, 456. ISBN 0-8412-1780-7.  

[edit] See also
Wikibooks has a book on the topic of 
General Chemistry/Redox ReactionsBessemer process 
Bioremediation 
Calvin cycle 
Citric acid cycle 
Electrochemical cell 
Electrochemistry 
Galvanic cell 
Membrane potential 
Oxidative addition and reductive elimination 
Reducing agent 
Thermic reaction 
Partial oxidation 

[edit] External links
Redox reactions calculator 
Redox reactions at Chemguide 
Online redox reaction equation balancer, balances equations of any half-cell and full reactions 
Retrieved from "http://en.wikipedia.org/wiki/Redox"
Categories: Organic redox reactions | Soil chemistry
 Lesson 6
PARTURITION

9-21. DEFINITION

Parturition is the process of childbirth.

9-22. INITIAL PHASE

The initial phase includes dilation (stretching) of the uterine cervix. At the appropriate moment, the amniotic membranes rupture and release the amniotic fluid.

9-23. PASSAGE OF THE FETUS

The release of amniotic fluid is followed by the passage of the fetus through the birth canal. 

During this passage, the newborn makes two partial rotations to accommodate the diameters of the relaxed bony pelvis. 
In the birthing process, there are several reflexes occurring at appropriate times. Natural childbirth (without anesthetics or similar devices) allows these reflexes to occur normally. Since the uterine wall musculature (myometrium) is not capable of expelling the fetus by itself, the mother must learn how to utilize the abdominal wall musculature in coordination with the uterine wall musculature to effect a normal childbirth. 
The head of the newborn presents itself in the perineum. If the central tendon of the perineum has not relaxed sufficiently, an episiotomy may be performed. This procedure involves cutting the posterior margin of the vagina to prevent tearing. Proper repair of the central tendon is essential to the proper recovering of the pelvis and perineum. 
After the birth of the newborn, the placenta and amniotic membranes ("afterbirth") are delivered. These are accompanied by a significant flow of blood. 
 
 Lesson 6
SOME PROTECTIVE MECHANISMS ASSOCIATED WITH THE HUMAN DIGESTIVE SYSTEM

6-23. CONTINUITY WITH SURROUNDING ENVIRONMENT

The human digestive system is essentially a continuous tube. It is open at both ends. Therefore, the lumen (cavity) connects directly with the surrounding environment.

a.      Along with the ingested food, almost anything can pass through the mouth into the digestive system. Almost anything does enter the digestive system.

b.      The digestive tract is open to the surrounding environment also at the other end, the anus.

6-24. COMMENT ABOUT THE RETICULOENDOTHELIAL SYSTEM

As indicated above, a variety of toxic materials and/or microorganisms may be included with the ingested foods. To protect against these undesired materials, special protective mechanisms are associated with the human digestive system. Such protective mechanisms are said to belong to the reticuloendothelial system. This term refers to the association of such mechanisms with a particular layer of epithelial cells.

6-25. COMMENT ABOUT LYMPHOID TISSUES

a.      The lymphocyte is an important type of white blood cell that is also found in the interspaces of a tissue called lymphoid (or lymphatic) tissue. Lymphocytes signal other types of white blood cells to phagocytize (engulf) foreign materials found within the body. The lymphoid tissues are particularly important in individuals from birth until about 15 years of age. The mass of lymphoid tissue found in the body of a 12-year-old is about twice the mass found in a full-grown adult. (Between 6 and 15 years of age, the immune system of the blood becomes the primary protector of the body from disease.)

b.      The lymphoid tissues are a primary component of the reticuloendothelial system.

6-26. TONSILS

Tonsils are aggregates of lymphoid tissue found at the beginning of the pharynx. There are three pairs of tonsils. Together, they form a ring of lymphoid tissue at the beginning of the pharynx. This ring, called Waldeyer's ring, completely surrounds the entrance to the pharynx from both the mouth (digestive entrance) and the nose and nasal chambers (respiratory entrance). 

a. In the upper recess of the pharynx is the pair of pharyngeal tonsils (commonly known as the adenoids). 
b. On either side, below the soft palate, are the palatine tonsils. These are the tonsils that one sees most frequently in small children. 
c. On the back of the root of the tongue are the lingual tonsils. 
6-27. "TONSILS" OF THE SMALL INTESTINES

Lymphoid aggregates of varying size are found in the walls of the small intestines. In the ileum portion, in particular, these aggregates are large enough to be easily observed and are called Peyer's patches. These might be considered "tonsils" of the small intestines.

6-28. "TONSILS" OF THE LARGE INTESTINE

At the beginning of the large intestine, at the inferior end of the cecum, is a structure known as the vermiform appendix. Since the vermiform appendix is actually a collection of lymphoid tissue, it should be considered the "tonsil" of the large intestine.

6-29. KUPFFER'S CELLS

As we have seen, blood from the absorptive areas of the gut tract is collected and delivered to the liver by the hepatic venous portal system. As this blood passes through the sinusoids (channels) of the liver, it is acted upon by cells called Kupffer's cells. These cells line the sinusoids. Since Kupffer's cells remove harmful substances from the blood, they are considered part of the reticuloendothelial system.

6-30. THE MAMMARY GLAND

a.      When the newborn baby is nursed by its mother, the initial secretion of the mammary glands is called colostrum. Although this colostrum lacks nutrients, it is loaded with antibodies. These antibodies provide the infant with its primary protection for the first 6 months of life.

b.      After a few days, the mammary gland produces the natural food for the human infant. As the infant suckles at the mother's breast, there is a certain amount of reflux (backward flow) into the milk ducts of the mammary gland. Should the infant develop an upper respiratory infection, the organisms causing the infection will be included in this reflux. Generally by the next time the infant suckles, the mammary gland will have produced the appropriate antibodies. These antibodies are delivered to the infant for its protection.
 
 Lesson 1
INTRODUCTION

7-1. PURPOSE OF RESPIRATION AND BREATHING 

The processes of respiration and breathing serve to provide oxygen to the body cells. This oxygen is used in the process of metabolic oxidation. In metabolic oxidation, the energy trapped in glucose molecules is released for use in the body's activities. 
Also, the carbon dioxide (CO2) produced during metabolic oxidation and any other unwanted gases are removed from the body. 
7-2. DEFINITIONS

a  Respiration. In general, respiration is the exchange of gases. In the human body, two kinds of respiration take place.

(1)  External respiration. In external respiration, gases are exchanged between the blood and the surrounding air. 
(2)  Internal respiration. In internal respiration, gases are exchanged between the blood and the individual cells of the body. 
b.  Breathing. On the other hand, breathing is the process by which air is moved into and out of the lungs.

(1)  Types. In humans, there are two types of breathing. In costal breathing, the rib cage is used. In diaphragmatic breathing, there is reciprocal interaction between the diaphragm and the abdominal wall. 
(2)  Direction of air flow. When the air flows inward, we call it inhalation (inspiration). When the air flows outward, we call it exhalation (expiration). 
7-3. PHYSICAL PRINCIPLES

Both respiration and breathing are essentially physical processes. Air and/or various gases are moved from one place to another. Their movement is because of differences in their relative pressures from one space to another. 

Pressure Gradient. Consider a situation in which there are two separate but connected spaces. If the concentration or pressure of that substance is greater in one space than the other, then there is a pressure gradient for that substance. As a result, the substance will move from the area of higher pressure to the area of lower pressure. 
Boyle's Law. Assume that we have a container and we can change the volume of the container without allowing a gas to escape. Boyle's law tells us that if we increase the volume, the pressure inside will decrease. Likewise, if we decrease the volume, the pressure inside will increase. 
Pascal's Law. If a closed container is filled with a fluid, a pressure applied to the fluid will produce an equal pressure at each and every point on the inner surface. 
Surface Area. Most phenomena in breathing and respiration take place at one surface or another. As surface area increases, more gases can be exchanged or treated. 
7-4. GENERAL ANATOMY AND CONSTRUCTION OF THE HUMAN TRUNK

The human trunk (Figure 7-1) can be considered a hollow cylinder. A muscular membrane, the thoracic diaphragm, extends across this hollow and divides the trunk into upper and lower cavities.

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0701.jpg]]

Figure 7-1. Schematic frontal section of the human trunk. 

Thoracic Cavity. The thoracic cavity is the space of the trunk above the diaphragm. It is open to the outside by way of the neck and head. Since the wall of the thorax is reinforced by special muscles, bones, and cartilages, we can consider the thorax to be a "solid-walled container" filled with gas. 
Abdominopelvic Cavity. The abdominopelvic cavity is the rest of the trunk cavity below the diaphragm. The abdominopelvic cavity is a closed system. Its walls are "elastic" since they are made up of musculature. The abdominopelvic cavity is filled with a fluid continuum. This fluid continuum consists primarily of water contained in the soft tissues of the abdomen and the pelvis. 
 
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5125488900878936930"><img src="http://lh5.google.com/cardwell.bob/RyFk_9UYq2I/AAAAAAAAByc/PoOT1cw8I30/s800/reflex.gif.jpg" /></a></html>
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5119523320999788562"><img src="http://lh4.google.com/cardwell.bob/RwwzVgeFQBI/AAAAAAAABYI/_o4RdSWofJU/s800/illu_pelvic_girdle.jpg" /></a></html>
Peripheral Nervous System

A nerve is a bundle of neuron processes wrapped in connective tissue coverings (endoneurium, perineurium, epineurium) (Figure 7.10). 

Cranial nerves: Twelve pairs of nerves that extend from the brain to serve the head and neck region. The exception is the vagus nerves, which extend into the thorax and abdomen. 

Spinal nerves: Thirty-one pairs of nerves are formed by the union of the dorsal and ventral roots of the spinal cord on each side. The spinal nerve proper is very short and splits into dorsal and ventral rami. Dorsal rami serve the posterior body trunk; ventral rami (except T1 through T12) form plexuses (cervical, brachial, lumbar, sacral) that serve the limbs. 

Autonomic nervous system: Part of the PNS, composed of neurons that regulate the activity of smooth and cardiac muscle and glands. This system differs from the somatic nervous system in that there is a chain of two motor neurons from the CNS to the effector. Two subdivisions serve the same organs with different effects (Figure 7.11). 

The sympathetic division is the "fight-or-flight" subdivision, which prepares the body to cope with some threat. Its activation results in increased heart rate and blood pressure. The pre-ganglionic neurons are in the gray matter of the cord. The postganglionic neurons are in sympathetic chains or in collateral ganglia. Postganglionic axons secrete norepinephrine. 

The parasympathetic division is the "housekeeping" system and is in control most of the time. This division maintains homeostasis by seeing that normal digestion and elimination occur, and that energy is conserved. The first motor neurons are in the brain or the sacral region of the cord. The second motor neurons are in the terminal ganglia close to the organ served. Postganglionic axons secrete acetylcholine. 
file:///D:/Tiddlewiki/My%20ANP%20TiddlyWiki/anp.html#%5B%5BNerve%20Cell%20Picture%5D%5D%20%5B%5BGENERAL%20SENSORY%20PATHWAYS%20OF%20THE%20HUMAN%20NERVOUS%20SYSTEM%5D%5D%20%5B%5BGENERAL%20VERSUS%20SPECIAL%20SENSES%20%5D%5D%20%5B%5BMOTOR%20PATHWAYS%20IN%20THE%20HUMAN%20NERVOUS%20SYSTEM%5D%5D%20%5B%5BMedulla%20oblongata%5D%5D%20Meninges%20%5B%5BNervous%20System%5D%5D%20%5B%5BNervous%20Tissue%5D%5D%20%5B%5BNervous%20Tissue%20Cells%5D%5D%20%5B%5BNervous%20system%5D%5D%20Neuroglia%20Neurons%20%5B%5BTHE%20AUTONOMIC%20NERVOUS%20SYSTEM%5D%5D%20%5B%5BTHE%20GENERAL%20REFLEX%20AND%20THE%20REFLEX%20ARC%5D%5D%20%5B%5BTHE%20NEURON%5D%5D%20%5B%5BTHE%20PERIPHERAL%20NERVOUS%20SYSTEM%20%5D%5D%20%5B%5BTHE%20SPECIAL%20SENSE%20OF%20SMELL%20(OLFACTION)%5D%5D%20%5B%5BTHE%20SPECIAL%20SENSE%20OF%20TASTE%20(GUSTATION)%5D%5D%20%5B%5BTHE%20SPECIAL%20SENSE%20OF%20VISION%5D%5D%20%5B%5BThe%20Nervous%20System%20Review%5D%5D%20%5B%5BThe%20Peripheral%20Nervous%20System%5D%5D%20%5B%5BUnit%2012%20The%20Human%20Nervous%20System%5D%5D%20%5B%5BUnit%20Five%5D%5D%20%5B%5BUnit%20Five-%20The%20Nervous%20System%5D%5D%20%5B%5Bglial%20cells%5D%5D%20meninges%20%5B%5Bnodes%20of%20Ranvier%5D%5D%20oligodendrocytes%20%5B%5Bsomatic%20nervous%20system%5D%5D%20%5B%5Bvisceral%20efferent%20nervous%20system%5D%5D
Phalanx bones
From Wikipedia, the free encyclopedia
• Find out more about navigating Wikipedia and finding information •Jump to: navigation, search
"Phalanges" redirects here. For the Lebanese Phalange, see the Kataeb Party. For the Spanish political party, see Falange.
 
The phalanges in a human hand 
Illustration of the phalangesThe name Phalanges is commonly given to the bones that form fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.

The phalanx do not really have individual names but are named after the digit, and their distance from the body.

Distal phalanges are at the tips of the fingers and toes. 
Proximal phalanges are closest to the hand (or foot) and articulate with the metacarpals of the hand, or metatarsals of the foot. 
Middle or Intermediate phalanges are between the distal and proximal. The thumb and big toe do not have middle phalanges. 
The term phalanx or phalanges refers to an ancient Greek army formation in which soldiers stand side by side, several rows deep, like an arrangement of fingers or toes.


[edit] Additional images

Upper extremity



 
Bones of the human hand.



 
Bones of the right foot. Plantar surface.



 


[edit] Reference
MedTerms.com Medical Dictionary 

[edit] See also
Phalanges of the foot 
Phalanges of the hand 
Phalanges Rock Band 
Retrieved from "http://en.wikipedia.org/wiki/Phalanx_bones"
Category: Long bones
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5125488896583969618"><img src="http://lh4.google.com/cardwell.bob/RyFk_tUYq1I/AAAAAAAAByU/VsTD08bPbVw/s800/potential.gif.jpg" /></a></html>
http://academic.pgcc.edu/~aimholtz/AandP/PracticeQuestions/ANPquestions.html
Prokaryotes do not have a nucleus, mitochondria or any other membrane bound organelles. In other words neither their DNA nor any other of their metabolic functions are collected together in a discrete membrane enclosed area. Instead everything is openly accessible within the cell, though some bacteria have internal membranes as sites of metabolic activity these membranes do not enclose a separate area of the cytoplasm. 
Pseudostratified columnar epithelium lines portions of the respiratory tract and some of the tubes of the male reproductive tract. 
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Chemical reaction
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For other uses, see Chemical reaction (disambiguation).
 
Vapours of hydrogen chloride in a beaker and ammonia in a test tube meet to form a cloud of a new substance, ammonium chlorideA chemical reaction is a process that results in the interconversion of chemical substances.[1] The substance or substances initially involved in a chemical reaction are called reactants. Chemical reactions are usually characterized by a chemical change, and they yield one or more products which are, in general, different from the reactants. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions.

Different chemical reactions are used in combinations in chemical synthesis in order to get a desired product. In biochemistry, series of chemical reactions catalyzed by enzymes form metabolic pathways, by which syntheses and decompositions ordinarily impossible in conditions within a cell are performed.

Contents [hide]
1 Reaction types 
2 Chemical kinetics 
3 See also 
4 References 
 


[edit] Reaction types
Although there are potentially many complex clasification systems for chemistry the system most commonly used by practising chemists (Zumdhal 1995:Chemical Principles) is very simple:

Precipitation Reactions where solutions are combined and a precipitate is formed, often a metalic salt 
acid-base reactions including neutralisation on combination of a (protonic) acid solution and a (hydroxyllic alkaline) solution to produce a salt and water :: HCl + NaOH → NaCl + H2O (described as a 'Displacement' reaction below, which is true, but rather unhelpful i think) but in the wider (Lewis Acid Base) sense including reactions described below (again rahter unhelpfully) ONLY as Metathesis reactions (shriver atkins langford:Inorganic Chemsitry 1990 p172) 
Oxidation-Reduction A.K.A. Redox reactions remember O.I.L.R.I.G: Oxidation Is Loss (of electrons) Reduction IS Gain (of electrons), this covers a multitude of reactions, and can even include acid base reactions really. It is the basis of combustion, and hence of metabolic chemistry, it is an excellent model for examining all other forms of organic chemistry as well. 

Chemical reactions may be classified in different ways depending on the aspect being considered and on one's approach on chemistry. Some examples of widely used terms for describing common kinds of reactions are:

Isomerisation, in which a chemical compound undergoes a structural rearrangement without any change in its net atomic composition; see stereoisomerism 
Direct combination or synthesis, in which two or more chemical elements or compounds unite to form a more complex product: 
N2 + 3H2 → 2NH3 
Chemical decomposition or analysis, in which a compound is decomposed into smaller compounds or elements: 
2H2O → 2H2 + O2 
Single displacement or substitution, characterized by an element being displaced out of a compound by a more reactive element: 
2Na(s) + 2HCl(aq) → 2NaCl(aq) + H2(g) 
Metathesis or Double displacement reaction, in which two compounds exchange ions or bonds to form different compounds: 
NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s) 
Combustion, in which any combustible substance combines with an oxidizing element, usually oxygen, to generate heat and form oxidized products. The term combustion is used usually only large-scale oxidation of whole molecules, i.e. a controlled oxidation of a single functional group is not combustion. 
C10H8+ 12O2 → 10CO2 + 4H2O 
CH2S + 6F2 → CF4 + 2 HF + SF6 
Some branches of chemistry include any detectable changes in chemical conformation in the reaction types, while others consider these changes merely as physical properties of a compound.

The collision of more than two particles into the ordered structure necessary to perform chemical transformations is extremely unlikely; which is why ternary reactions in practice are not observed. A chemical reaction may require three or more reagents, but the process can generally be best described as a stepwise series of elementary reactions.

The large diversity of chemical reactions makes it difficult to establish simple criteria for functional (as opposed to mechanistic) classification. However, some kinds of reactions have similarities which make it possible to define some larger groups. A few examples are:

Organic reactions encompass several different kinds of reactions involving compounds which have carbon as the main element in their molecular structure. These reactions occur mostly according to, within, by, or via functional groups. 
Petrochemical reactions are often distinguished from other organic reactions. 
Redox reactions involve augmenting or decreasing the electrons associated with a particular atom. according to its oxidation number. 
Combustion, in which a substance reacts with an oxidizing element, such as oxygen gas. 
Reactions can also be classified according to their mechanism, some typical examples being:

Reactions of ions, e.g. disproportionation of hypochlorite 
Reactions with reactive ionic intermediates, e.g. reactions of enolates 
Radical reactions, e.g. combustion at high temperature 
Reactions of carbenes 

[edit] Chemical kinetics
Main article: Chemical kinetics
The rate of a chemical reaction is a measure of how the concentration or pressure of the involved substances changes with time. Analysis of reaction rates is important for several applications, such as in chemical engineering or in chemical equilibrium study. Rates of reaction depends basically on:

Reactant concentrations, which usually make the reaction happen at a faster rate if raised through increased collisions per unit time, 
Surface area, the amount of the substance being used, 
Pressure, by increasing the pressure, you decrease the volume between molecules. This will increase the frequency of collisions of molecules. 
Activation energy, which is defined as the amount of energy required to make the reaction start and carry on spontaneously. Higher activation energy implies that the reactants need more energy to start than a reaction with a lower activation energy. 
Temperature, which hastens reactions if raised, since higher temperature increases the energy of the molecules, creating more collisions per unit time, 
The presence or absence of a catalyst. Catalysts are substances which change the pathway (mechanism) of a reaction which in turn increases the speed of a reaction by lowering the activation energy needed for the reaction to take place. A catalyst is not destroyed or changed during a reaction, so it can be used again. 
For some reactions, the presence of electromagnetic radiation, most notably ultra violet, is needed to promote the breaking of bonds to start the reaction. This is particularly true for reactions involving radicals. 
Reaction rates are related to the concentrations of substances involved in reactions, as quantified by the rate law of each reaction. Note that some reactions have rates that are independent of reactant concentrations. These are called zero order reactions.


[edit] See also
List of reactions 
Organic reaction 
Inorganic chemical reaction 
List of important publications in chemistry 
Stoichiometry 
Stoichiometric coefficient 
Transition state theory 
Gas stoichiometry 
Thermodynamic databases for pure substances 

[edit] References
^ International Union of Pure and Applied Chemistry. "chemical reaction". Compendium of Chemical Terminology Internet edition. 
Retrieved from "http://en.wikipedia.org/wiki/Chemical_reaction"
Categories: Chemical reactions | Chemistry
Redox
From Wikipedia, the free encyclopedia
(Redirected from Reduction (chemistry))• Learn more about citing Wikipedia •Jump to: navigation, search
“Reduced” redirects here. For other uses, see reduction.
 
Illustration of a redox reactionRedox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed.

This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide, or the reduction of carbon by hydrogen to yield methane (CH4), or it can be a complex process such as the oxidation of sugar in the human body through a series of very complex electron transfer processes.

The term redox comes from the two concepts of reduction and oxidation. It can be explained in simple terms:

Oxidation describes the loss of electrons by a molecule, atom or ion 
Reduction describes the gain of electrons by a molecule, atom or ion 
However, these descriptions (though sufficient for many purposes) are not truly correct. Oxidation and reduction properly refer to a change in oxidation number — the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. In practice, the transfer of electrons will always cause a change in oxidation number, but there are many reactions which are classed as "redox" even though no electron transfer occurs (such as those involving covalent bonds).

Non-redox reactions, which do not involve changes in formal charge, are known as metathesis reactions.

 
The two parts of a redox reaction 
Rusting iron 
A bonfire. Combustion consists of redox reactions involving free radicals.Contents [hide]
1 Oxidizing and reducing agents 
2 Oxidation in industry 
3 Examples of redox reactions 
3.1 Other examples 
4 Redox reactions in biology 
5 Redox cycling 
6 References 
7 See also 
8 External links 
 


[edit] Oxidizing and reducing agents
Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. Put in another way, the oxidant removes electrons from another substance, and is thus reduced itself. And because it "accepts" electrons it is also called an electron acceptor.

Oxidants are usually chemical substances with elements in high oxidation numbers (e.g., H2O2, MnO4−, CrO3, Cr2O72−, OsO4) or highly electronegative substances that can gain one or two extra electrons by oxidizing a substance (O, F, Cl, Br).

Substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. Put in another way, the reductant transfers electrons to another substance, and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor. Reductants in chemistry are very diverse. Metal reduction - electropositive elemental metals can be used (Li, Na, Mg, Fe, Zn, Al). These metals donate or give away electrons readily. Other kinds of reductants are hydride transfer reagents (NaBH4, LiAlH4), these reagents are widely used in organic chemistry[1][2], primarily in the reduction of carbonyl compounds to alcohols. Another useful method is reductions involving hydrogen gas (H2) with a palladium, platinum, or nickel catalyst. These catalytic reductions are primarily used in the reduction of carbon-carbon double or triple bonds.

The chemical way to look at redox processes is that the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or reducing agent loses electrons and is oxidized and the oxidant or oxidizing agent gains electrons and is reduced. The pair of an oxidising and reducing agent that are involved in a particular reaction is called a redox pair.


[edit] Oxidation in industry
Oxidation is used in a wide variety of industries such as in the production of cleaning products.

Redox reactions are the foundation of electrochemical cells.


[edit] Examples of redox reactions
A good example is the reaction between hydrogen and fluorine:

 
We can write this overall reaction as two half-reactions: the oxidation reaction

 
and the reduction reaction:

 
Analysing each half-reaction in isolation can often make the overall chemical process clearer. Because there is no net change in charge during a redox reaction, the number of electrons in excess in the oxidation reaction must equal the number consumed by the reduction reaction (as shown above).

Elements, even in molecular form, always have an oxidation number of zero. In the first half reaction, hydrogen is oxidized from an oxidation number of zero to an oxidation number of +1. In the second half reaction, fluorine is reduced from an oxidation number of zero to an oxidation number of −1.

When adding the reactions together the electrons cancel:

 
And the ions combine to form hydrogen fluoride:

 

[edit] Other examples
iron(II) oxidizes to iron(III): 
Fe2+ → Fe3+ + e− 
hydrogen peroxide reduces to hydroxide in the presence of an acid: 
H2O2 + 2 e− → 2 OH− 
overall equation for the above:

2Fe2+ + H2O2 + 2H+ → 2Fe3+ + 2H2O 
denitrification, nitrate reduces to nitrogen in the presence of an acid: 
2NO3− + 10e− + 12 H+ → N2 + 6H2O 
iron oxidizes to iron(III) oxide and oxygen is reduced forming iron(III) oxide (commonly known as rusting, which is similar to tarnishing): 
4Fe + 3O2 → 2 Fe2O3 
Combustion of hydrocarbons, e.g. in an internal combustion engine, produces water, carbon dioxide, some partially oxidized forms such as carbon monoxide and heat energy. Complete oxidation of materials containing carbon produces carbon dioxide. 
In organic chemistry, stepwise oxidation of a hydrocarbon produces water and, successively, an alcohol, an aldehyde or a ketone, carboxylic acid, and then a peroxide. 
In biology many important processes involve redox reactions. Cell respiration, for instance, is the oxidation of glucose (C6H12O6) to CO2 and the reduction of oxygen to water. The summary equation for cell respiration is: 
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O 
The process of cell respiration also depends heavily on the reduction of NAD+ to NADH and the reverse reaction (the oxidation of NADH to NAD+). Photosynthesis is essentially the reverse of the redox reaction in cell respiration: 
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 

[edit] Redox reactions in biology
 
 
Top: ascorbic acid (reduced form of Vitamin C)
Bottom: dehydroascorbic acid (oxidized form of Vitamin C)Much biological energy is stored and released by means of redox reactions. Photosynthesis involves the reduction of carbon dioxide into sugars and the oxidation of water into molecular oxygen. The reverse reaction, respiration, oxidizes sugars to produce carbon dioxide and water. As intermediate steps, the reduced carbon compounds are used to reduce nicotinamide adenine dinucleotide (NAD+), which then contributes to the creation of a proton gradient, which drives the synthesis of adenosine triphosphate (ATP) and is maintained by the reduction of oxygen. In animal cells, mitochondria perform similar functions. See Membrane potential article.

The term redox state is often used to describe the balance of NAD+/NADH and NADP+/NADPH in a biological system such as a cell or organ. The redox state is reflected in the balance of several sets of metabolites (e.g., lactate and pyruvate, beta-hydroxybutyrate and acetoacetate) whose interconversion is dependent on these ratios. An abnormal redox state can develop in a variety of deleterious situations, such as hypoxia, shock, and sepsis. Redox signaling involves the control of cellular processes by redox processes.


[edit] Redox cycling
A wide variety of aromatic compounds are enzymatically reduced to form free radicals that contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes and their coenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide and regenerate the unchanged parent compound. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen to form superoxide. This catalytic behavior has been described as futile cycle or redox cycling.

Examples of redox cycling-inducing molecules are the herbicide paraquat and other viologens and quinones such as menadione. [1]PDF (2.76 MiB)


[edit] References
^ Hudlický, Miloš (1996). Reductions in Organic Chemistry. Washington, D.C.: American Chemical Society, 429. ISBN 0-8412-3344-6.  
^ Hudlický, Miloš (1990). Oxidations in Organic Chemistry. Washington, D.C.: American Chemical Society, 456. ISBN 0-8412-1780-7.  

[edit] See also
Wikibooks has a book on the topic of 
General Chemistry/Redox ReactionsBessemer process 
Bioremediation 
Calvin cycle 
Citric acid cycle 
Electrochemical cell 
Electrochemistry 
Galvanic cell 
Membrane potential 
Oxidative addition and reductive elimination 
Reducing agent 
Thermic reaction 
Partial oxidation 

[edit] External links
Redox reactions calculator 
Redox reactions at Chemguide 
Online redox reaction equation balancer, balances equations of any half-cell and full reactions 
Retrieved from "http://en.wikipedia.org/wiki/Redox"
Categories: Organic redox reactions | Soil chemistry
 
 
http://lrn.org/Content/Lessons/respiratory.html
 



Functional Anatomy of the Respiratory System

The nasal cavity, the chamber within the nose, is divided medially by a nasal septum and separated from the oral cavity by the palate(Figure 13.1). The nasal cavity is lined with a mucosa, which warms, filters, and moistens incoming air. The mucosa also contains receptors for sense of smell. Paranasal sinuses and nasolacrimal ducts drain into the nasal cavity. 

The pharynx (throat) is a mucosa-lined, muscular tube with three regions nasopharynx, oropharynx, and laryngopharynx. The nasopharynx functions in respiration only; the others serve both respiratory and digestive functions. The pharynx contains tonsils, which act as part of the body's defense system. 

The larynx (voice box) is a cartilage structure; most prominent is the thyroid cartilage (Adam's apple). The larynx connects the pharynx with the trachea below. The laryngeal opening (glottis) is hooded by the epiglottis, which prevents entry of food or drink into respiratory passages when swallowing. The larynx contains the true vocal cords, which produce sounds used in speech. 

The trachea (windpipe) extends from larynx to primary bronchi. The trachea is a smooth muscle tube lined with a ciliated mucosa and reinforced with C-shaped cartilage rings, which keep the trachea open. 

Right and left primary bronchi result from subdivision of the trachea. Each plunges into the hilus of the lung on its side. 

The lungs are paired organs flanking the mediastinum in the thoracic cavity. The lungs are covered with visceral pleura; the thorax wall is lined with parietal pleura. Pleural secretions decrease friction during breathing. The lungs are primarily elastic tissue, plus passageways of the respiratory tree. The smallest passageways end in clusters of alveoli. 

The conducting zone includes all respiratory passages from the nasal cavity to the terminal bronchioles; they conduct air to and from the lungs. Respiratory bronchioles, alveolar ducts and sacs, and alveoli which have thin walls through which gas exchanges are made with pulmonary capillary blood are respiratory zone structures (Figure 13.2). 


Respiratory Physiology

Mechanics of breathing: Gas travels from high-pressure to low-pressure areas. Pressure outside the body is atmospheric pressure; pressure inside the lungs is intrapulmonary pressure; pressure in the intrapleural space is intrapleural pressure (which is always negative). Movement of air into and out of the lungs is called pulmonary ventilation, or breathing (Figure 13.3). When inspiratory muscles contract, intrapulmonary volume increases, its pressure decreases, and air rushes in (inspiration). When inspiratory muscles relax, the lungs recoil and air rushes out (expiration). Expansion of the lungs is helped by cohesion between pleurae and by the presence of surfactant in alveoli. 

Nonrespiratory air movements: Nonrespiratory air movements are voluntary or reflex activities that move air into or out of the lungs. These include coughing, sneezing, laughing, crying, hiccuping, yawning. 

Respiratory volumes and capacities: Air volumes exchanged during breathing are tidal volume, inspiratory reserve volume, expiratory reserve volume, and vital capacity (Figure 13.4). Residual volume is non-exchangeable respiratory volume and allows gas exchange to go on continually. 

Respiratory sounds: Bronchial sounds are sounds of air passing through large respiratory passageways. Vesicular breathing sounds occur as air fills alveoli. 

External respiration, gas transport, and internal respiration: Gases move according to laws of diffusion (Figure 13.5). Oxygen moves from alveolar air into pulmonary blood. Most oxygen is transported bound to hemoglobin inside RBCs. Carbon dioxide moves from pulmonary blood into alveolar air. Most carbon dioxide is transported as bicarbonate ion in plasma. At body tissues, oxygen moves from blood to the tissues, whereas carbon dioxide moves from the tissues to blood. 

Control of respiration 

Nervous control: Neural centers for control of respiratory rhythm are in the medulla and pons. Reflex arcs initiated by stretch receptors in the lungs also play a role in respiration by notifying neural centers of excessive overinflation. 

Physical factors: Increased body temperature, exercise, speech, singing, and nonrespiratory air movements modify both rate and depth of breathing. 

Volition: To a degree, breathing may be consciously controlled if it does not interfere with homeostasis. 

Emotional factors: Some emotional stimuli can modify breathing. Examples are fear, anger, and excitement. 

Chemical factors: Changes in blood levels of carbon dioxide are the most important stimuli affecting respiratory rhythm and depth. Carbon dioxide acts directly on the medulla via its effect on reducing blood pH. Rising levels of carbon dioxide in blood result in faster, deeper breathing; falling levels lead to shallow, slow breathing. Hyperventilation may result in apnea and dizziness, due to alkalosis. Oxygen is less important as a respiratory stimulus in normal, healthy people, but it is the stimulus for those whose systems have become accustomed to high levels of carbon dioxide. 



Respiratory Disorders

The major respiratory disorders are emphysema, chronic bronchitis, and lung cancer. A significant cause is cigarette smoking. 

Emphysema is characterized by permanent enlargement and destruction of alveoli. The lungs lose their elasticity, and expiration becomes an active process. 

Chronic bronchitis is characterized by excessive mucus production and its pooling in lower respiratory passageways, which severely impairs ventilation and gas exchange. Patients may become cyanotic as a result of chronic hypoxia. 

Lung cancer is extremely aggressive and metastasizes rapidly. The three most common lung cancers are squamous cell carcinoma, adenocarcinoma, and small cell carcinoma. 
 


Developmental Aspects of the Respiratory System

Premature infants have problems keeping their lungs inflated due to lack of surfactant in their alveoli. (Surfactant is formed late in pregnancy.) 

The most important birth defects of the respiratory system are cleft palate and cystic fibrosis. 

The lungs continue to mature until young adulthood. 

During youth and middle age, most respiratory system problems are a result of external factors, such as infections and substances that physically block respiratory passageways. 

In old age, the thorax becomes more rigid and lungs become less elastic, leading to decreased vital capacity. Protective mechanisms of the respiratory system decrease in effectiveness in elderly persons, predisposing them to more respiratory tract infections. 
      

Functional Anatomy of the Respiratory System

The nasal cavity, the chamber within the nose, is divided medially by a nasal septum and separated from the oral cavity by the palate(Figure 13.1). The nasal cavity is lined with a mucosa, which warms, filters, and moistens incoming air. The mucosa also contains receptors for sense of smell. Paranasal sinuses and nasolacrimal ducts drain into the nasal cavity. 

The pharynx (throat) is a mucosa-lined, muscular tube with three regions nasopharynx, oropharynx, and laryngopharynx. The nasopharynx functions in respiration only; the others serve both respiratory and digestive functions. The pharynx contains tonsils, which act as part of the body's defense system. 

The larynx (voice box) is a cartilage structure; most prominent is the thyroid cartilage (Adam's apple). The larynx connects the pharynx with the trachea below. The laryngeal opening (glottis) is hooded by the epiglottis, which prevents entry of food or drink into respiratory passages when swallowing. The larynx contains the true vocal cords, which produce sounds used in speech. 

The trachea (windpipe) extends from larynx to primary bronchi. The trachea is a smooth muscle tube lined with a ciliated mucosa and reinforced with C-shaped cartilage rings, which keep the trachea open. 

Right and left primary bronchi result from subdivision of the trachea. Each plunges into the hilus of the lung on its side. 

The lungs are paired organs flanking the mediastinum in the thoracic cavity. The lungs are covered with visceral pleura; the thorax wall is lined with parietal pleura. Pleural secretions decrease friction during breathing. The lungs are primarily elastic tissue, plus passageways of the respiratory tree. The smallest passageways end in clusters of alveoli. 

The conducting zone includes all respiratory passages from the nasal cavity to the terminal bronchioles; they conduct air to and from the lungs. Respiratory bronchioles, alveolar ducts and sacs, and alveoli which have thin walls through which gas exchanges are made with pulmonary capillary blood are respiratory zone structures (Figure 13.2). 



Respiratory Physiology

Mechanics of breathing: Gas travels from high-pressure to low-pressure areas. Pressure outside the body is atmospheric pressure; pressure inside the lungs is intrapulmonary pressure; pressure in the intrapleural space is intrapleural pressure (which is always negative). Movement of air into and out of the lungs is called pulmonary ventilation, or breathing (Figure 13.3). When inspiratory muscles contract, intrapulmonary volume increases, its pressure decreases, and air rushes in (inspiration). When inspiratory muscles relax, the lungs recoil and air rushes out (expiration). Expansion of the lungs is helped by cohesion between pleurae and by the presence of surfactant in alveoli. 

Nonrespiratory air movements: Nonrespiratory air movements are voluntary or reflex activities that move air into or out of the lungs. These include coughing, sneezing, laughing, crying, hiccuping, yawning. 

Respiratory volumes and capacities: Air volumes exchanged during breathing are tidal volume, inspiratory reserve volume, expiratory reserve volume, and vital capacity (Figure 13.4). Residual volume is non-exchangeable respiratory volume and allows gas exchange to go on continually. 

Respiratory sounds: Bronchial sounds are sounds of air passing through large respiratory passageways. Vesicular breathing sounds occur as air fills alveoli. 

External respiration, gas transport, and internal respiration: Gases move according to laws of diffusion (Figure 13.5). Oxygen moves from alveolar air into pulmonary blood. Most oxygen is transported bound to hemoglobin inside RBCs. Carbon dioxide moves from pulmonary blood into alveolar air. Most carbon dioxide is transported as bicarbonate ion in plasma. At body tissues, oxygen moves from blood to the tissues, whereas carbon dioxide moves from the tissues to blood. 

Control of respiration 

Nervous control: Neural centers for control of respiratory rhythm are in the medulla and pons. Reflex arcs initiated by stretch receptors in the lungs also play a role in respiration by notifying neural centers of excessive overinflation. 

Physical factors: Increased body temperature, exercise, speech, singing, and nonrespiratory air movements modify both rate and depth of breathing. 

Volition: To a degree, breathing may be consciously controlled if it does not interfere with homeostasis. 

Emotional factors: Some emotional stimuli can modify breathing. Examples are fear, anger, and excitement. 

Chemical factors: Changes in blood levels of carbon dioxide are the most important stimuli affecting respiratory rhythm and depth. Carbon dioxide acts directly on the medulla via its effect on reducing blood pH. Rising levels of carbon dioxide in blood result in faster, deeper breathing; falling levels lead to shallow, slow breathing. Hyperventilation may result in apnea and dizziness, due to alkalosis. Oxygen is less important as a respiratory stimulus in normal, healthy people, but it is the stimulus for those whose systems have become accustomed to high levels of carbon dioxide. 



Respiratory Disorders

The major respiratory disorders are emphysema, chronic bronchitis, and lung cancer. A significant cause is cigarette smoking. 

Emphysema is characterized by permanent enlargement and destruction of alveoli. The lungs lose their elasticity, and expiration becomes an active process. 

Chronic bronchitis is characterized by excessive mucus production and its pooling in lower respiratory passageways, which severely impairs ventilation and gas exchange. Patients may become cyanotic as a result of chronic hypoxia. 

Lung cancer is extremely aggressive and metastasizes rapidly. The three most common lung cancers are squamous cell carcinoma, adenocarcinoma, and small cell carcinoma. 



Developmental Aspects of the Respiratory System

Premature infants have problems keeping their lungs inflated due to lack of surfactant in their alveoli. (Surfactant is formed late in pregnancy.) 

The most important birth defects of the respiratory system are cleft palate and cystic fibrosis. 

The lungs continue to mature until young adulthood. 

During youth and middle age, most respiratory system problems are a result of external factors, such as infections and substances that physically block respiratory passageways. 

In old age, the thorax becomes more rigid and lungs become less elastic, leading to decreased vital capacity. Protective mechanisms of the respiratory system decrease in effectiveness in elderly persons, predisposing them to more respiratory tract infections. 

     


Functional Anatomy of the Respiratory System

The nasal cavity, the chamber within the nose, is divided medially by a nasal septum and separated from the oral cavity by the palate(Figure 13.1). The nasal cavity is lined with a mucosa, which warms, filters, and moistens incoming air. The mucosa also contains receptors for sense of smell. Paranasal sinuses and nasolacrimal ducts drain into the nasal cavity. 

The pharynx (throat) is a mucosa-lined, muscular tube with three regions nasopharynx, oropharynx, and laryngopharynx. The nasopharynx functions in respiration only; the others serve both respiratory and digestive functions. The pharynx contains tonsils, which act as part of the body's defense system. 

The larynx (voice box) is a cartilage structure; most prominent is the thyroid cartilage (Adam's apple). The larynx connects the pharynx with the trachea below. The laryngeal opening (glottis) is hooded by the epiglottis, which prevents entry of food or drink into respiratory passages when swallowing. The larynx contains the true vocal cords, which produce sounds used in speech. 

The trachea (windpipe) extends from larynx to primary bronchi. The trachea is a smooth muscle tube lined with a ciliated mucosa and reinforced with C-shaped cartilage rings, which keep the trachea open. 

Right and left primary bronchi result from subdivision of the trachea. Each plunges into the hilus of the lung on its side. 

The lungs are paired organs flanking the mediastinum in the thoracic cavity. The lungs are covered with visceral pleura; the thorax wall is lined with parietal pleura. Pleural secretions decrease friction during breathing. The lungs are primarily elastic tissue, plus passageways of the respiratory tree. The smallest passageways end in clusters of alveoli. 

The conducting zone includes all respiratory passages from the nasal cavity to the terminal bronchioles; they conduct air to and from the lungs. Respiratory bronchioles, alveolar ducts and sacs, and alveoli which have thin walls through which gas exchanges are made with pulmonary capillary blood are respiratory zone structures (Figure 13.2). 



Respiratory Physiology

Mechanics of breathing: Gas travels from high-pressure to low-pressure areas. Pressure outside the body is atmospheric pressure; pressure inside the lungs is intrapulmonary pressure; pressure in the intrapleural space is intrapleural pressure (which is always negative). Movement of air into and out of the lungs is called pulmonary ventilation, or breathing (Figure 13.3). When inspiratory muscles contract, intrapulmonary volume increases, its pressure decreases, and air rushes in (inspiration). When inspiratory muscles relax, the lungs recoil and air rushes out (expiration). Expansion of the lungs is helped by cohesion between pleurae and by the presence of surfactant in alveoli. 

Nonrespiratory air movements: Nonrespiratory air movements are voluntary or reflex activities that move air into or out of the lungs. These include coughing, sneezing, laughing, crying, hiccuping, yawning. 

Respiratory volumes and capacities: Air volumes exchanged during breathing are tidal volume, inspiratory reserve volume, expiratory reserve volume, and vital capacity (Figure 13.4). Residual volume is non-exchangeable respiratory volume and allows gas exchange to go on continually. 

Respiratory sounds: Bronchial sounds are sounds of air passing through large respiratory passageways. Vesicular breathing sounds occur as air fills alveoli. 

External respiration, gas transport, and internal respiration: Gases move according to laws of diffusion (Figure 13.5). Oxygen moves from alveolar air into pulmonary blood. Most oxygen is transported bound to hemoglobin inside RBCs. Carbon dioxide moves from pulmonary blood into alveolar air. Most carbon dioxide is transported as bicarbonate ion in plasma. At body tissues, oxygen moves from blood to the tissues, whereas carbon dioxide moves from the tissues to blood. 

Control of respiration 

Nervous control: Neural centers for control of respiratory rhythm are in the medulla and pons. Reflex arcs initiated by stretch receptors in the lungs also play a role in respiration by notifying neural centers of excessive overinflation. 

Physical factors: Increased body temperature, exercise, speech, singing, and nonrespiratory air movements modify both rate and depth of breathing. 

Volition: To a degree, breathing may be consciously controlled if it does not interfere with homeostasis. 

Emotional factors: Some emotional stimuli can modify breathing. Examples are fear, anger, and excitement. 

Chemical factors: Changes in blood levels of carbon dioxide are the most important stimuli affecting respiratory rhythm and depth. Carbon dioxide acts directly on the medulla via its effect on reducing blood pH. Rising levels of carbon dioxide in blood result in faster, deeper breathing; falling levels lead to shallow, slow breathing. Hyperventilation may result in apnea and dizziness, due to alkalosis. Oxygen is less important as a respiratory stimulus in normal, healthy people, but it is the stimulus for those whose systems have become accustomed to high levels of carbon dioxide. 



Respiratory Disorders

The major respiratory disorders are emphysema, chronic bronchitis, and lung cancer. A significant cause is cigarette smoking. 

Emphysema is characterized by permanent enlargement and destruction of alveoli. The lungs lose their elasticity, and expiration becomes an active process. 

Chronic bronchitis is characterized by excessive mucus production and its pooling in lower respiratory passageways, which severely impairs ventilation and gas exchange. Patients may become cyanotic as a result of chronic hypoxia. 

Lung cancer is extremely aggressive and metastasizes rapidly. The three most common lung cancers are squamous cell carcinoma, adenocarcinoma, and small cell carcinoma. 



Developmental Aspects of the Respiratory System

Premature infants have problems keeping their lungs inflated due to lack of surfactant in their alveoli. (Surfactant is formed late in pregnancy.) 

The most important birth defects of the respiratory system are cleft palate and cystic fibrosis. 

The lungs continue to mature until young adulthood. 

During youth and middle age, most respiratory system problems are a result of external factors, such as infections and substances that physically block respiratory passageways. 

In old age, the thorax becomes more rigid and lungs become less elastic, leading to decreased vital capacity. Protective mechanisms of the respiratory system decrease in effectiveness in elderly persons, predisposing them to more respiratory tract infections. 

[img[http://lrn.org/Graphics/Respiratory/figure%2013.1.gif]]

[img[http://lrn.org/Graphics/Respiratory/figure%2013.2.gif]]

[img[http://lrn.org/Graphics/Respiratory/figure%2013.3.gif]]

[img[http://lrn.org/Graphics/Respiratory/figure%2013.4.gif]]

[img[http://lrn.org/Graphics/Respiratory/figure%2013.5.gif]]
 

Here is a photo of Rick from 1974
[img[http://bp0.blogger.com/_fwukQ1dvAw8/RvmdVhwzcxI/AAAAAAAABLQ/puGmx3Ow1WE/s400/rick21974.jpeg" border="0" alt=""id="BLOGGER_PHOTO_ID_5114291845021790994"]]

Here is a photo of Rick from 2007
[img[http://bp0.blogger.com/_fwukQ1dvAw8/RvmddhwzcyI/AAAAAAAABLY/wJshgGwITqM/s400/rickbrace.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5114291982460744482"]]

[img[http://photos1.blogger.com/img/261/2778/400/gohell.jpg]]
 Lesson 4
THE SPECIAL SENSE OF EQUILIBRIUM, THE GENERAL BODY SENSE, AND POSTURAL REFLEXES

13-15. INTRODUCTION 

The human body is composed of a series of linkages, block on top of block. These blocks can be arranged in a multitude of patterns called postures. In order to produce and control these postures, the human brain utilizes a great number of continuous inputs telling the brain the instantaneous condition of the body posture. Overall, we refer to this process as the general body sense. 
The internal ear provides one of the input systems for the general body sense. The internal ear responds to gravitational forces, of which there are two kinds--static and kinetic (in motion). Of the kinetic stimuli, the motion may be in a straight line (linear) or angular (curvilinear). 
13-16. THE MACULAE

The membranous labyrinth of the internal ear has two sac-like parts--the sacculus and the utriculus. On the wall of each of these sacs is a collection of hair cells known as the macula (plural: maculae). The hairs of these hair cells move in response to gravitational forces, both static and linear kinetic. The maculae are particularly sensitive to small changes in the orientation of the head from an upright position. Thus, the maculae are very important in maintaining a standing or upright position.

13-17. THE SEMICIRCULAR DUCTS 

In addition, three tubular structures are associated with the utriculus. The circle of each of these semicircular ducts is completed by the cavity of the utriculus. At one end of each semicircular duct is a crista, a ridge of hair cells across the axis of the duct. 
When a jet takes off, a passenger tends to remain in place at first and can feel the resulting pressure of the seat against his back. Also, when the jet is no longer accelerating, the passenger can feel that the pressure of the seat against his back has returned to normal. 
Likewise, in the appropriate semicircular duct, the endolymph ("passenger") tends to remain in place early during an acceleration. Because the duct ("seat") itself is moving with the body ("jet"), the hairs of the crista are affected by the change in movement. Later, when acceleration stops, the effect upon the hairs of the crista is also registered. 
However, the cristae of the semicircular ducts detect rotation of the head (angular acceleration and angular velocity). Linear acceleration, as with our example of the passenger and the jet, is detected primarily by the maculae, discussed above. 
13-18. RESULTING INPUTS FOR THE SPECIAL SENSE OF EQUILIBRIUM

The combined inputs from the maculae of the sacs and the cristae of the semicircular ducts provide continuous, instantaneous information about the specific location and posture of the head in relationship to the center of gravity of the earth. These inputs are transmitted by the vestibular neurons to the hindbrainstem.

13-19. INPUTS FOR THE GENERAL BODY SENSE

In addition to the inputs from the membranous labyrinth, various other inputs are used to continuously monitor the second-to-second posture of the human body. 

We have already examined the proprioceptive sense, which monitors the condition of the muscles of the body. 
Various other receptors are associated with the joint capsules, the integument, etc. They indicate the precise degree of bending present in the body. 
A very important body sense is vision. Even when other inputs are lacking, if an individual can see his feet, he may still be able to stand and move. 
13-20. POSTURAL REFLEXES

To automatically control the posture, the human nervous system has a number of special reflexes. These reflexes are coordinated through the cerebellum. 

The head and neck tonic reflexes orient the upper torso in relationship to the head. 
Another set of reflexes does likewise for the body in general. The righting reflexes come into play when the body falls out of balance or equilibrium. 
A special set of reflexes connects the vestibular apparatus to the extraocular muscles of the eyeball. This was discussed earlier in the section on the special sense of the vision. 
 
 Lesson 6
SESAMOID BONES

4-13. GENERAL

The sesamoid bones are another kind of bone. Sesamoid bones develop in place within tendons of skeletal muscles where the tendons sustain excessive pressures. Since the sesamoid bone absorbs these pressures, it protects the tendon from wear and tear.

4-14. EXAMPLE-PATELLA

The primary example of sesamoid bones is the patella (kneecap). In the form of a simple pulley mechanism, the tendon of the quadriceps femoris muscle passes over the distal end of the femur. Located at this point within the tendon is the patella.
 
 Lesson 5
SUBCUTANEOUS LAYER

3-20. INTRODUCTION

Between the integument proper and the investing deep fascia is the middle layer called the subcutaneous layer.

SUB = under CUTANEOUS = skin

In general, the subcutaneous layer is made up primarily of loose areolar FCT and fat. The fat tends to be localized in special areas that are different in the two sexes. (In affluent societies, there may be general obesity rather than localized fat.)

3-21. CUTANEOUS NAVL

Also found in the subcutaneous layer are the cutaneous NAVL (nerves, arteries, veins, lymphatics). In addition, some of the sensory receptors of the nervous system actually extend from the subcutaneous layer up into the papillae of the dermis, immediately below the epidermis.

Cutaneous Capillaries. The cutaneous capillaries of the subcutaneous layer tend to be localized at two levels. First, there is a superficial layer near the underside of the dermis. Second, there is a deeper layer near the investing deep fascia. These two layers of capillaries are more or less separated by the fatty tissue in the subcutaneous layer.

Sensory Innervations. If one looks at a zebra or a tiger, one can immediately see that the fur of these animals has a belt-like color pattern. There is also a belt-like pattern in the integument of humans. It is not a pattern of colors, as with zebras and tigers. It is a pattern of sensory innervations. A "belt" is innervated by a specific spinal nerve, left and right. This belt-like area is called a dermatome. We refer to the nerves supplying these areas as segmental nerves because they "segment" the integument into dermatomes. Except for the three dermatomes of the face, there is an overlap of adjacent dermatomes.

3-22. INTEGUMENTARY MUSCLES

Also associated with the subcutaneous layer are a number of integumentary muscles.

Facial Muscles. As the term implies, facial muscles are associated with the face. Facial muscles are mainly involved with the various openings of the face. They are able to open and close these openings. Because they are also used in visual communication, they are sometimes called mimetic muscles ("muscles of expression").

Arrector Pili Muscles. Another group of integumentary muscles is known as the arrector pili muscles. Ordinarily, the hairs and the hair follicles are at an angle to the skin rather than perpendicular (straight up or down). At times of emotional stress, the arrector pili muscles contract. In hairy areas, the contraction of these muscles, attached to the follicles, causes the hairs to stand "straight up." In glabrous areas, their contraction produces "goose bumps."
 
 Lesson 9
SUPERFICIAL WOUND HEALING

3-35. INTRODUCTION

A wound of the integument creates an opening. This opening is an avenue for infection and water loss.

3-36. RELATIONSHIP WITH SPLIT LINES

A wound crossing the split lines of the dermis tends to gape open. A wound parallel to the split lines closes easily. For this reason, when a surgeon can choose an incision, he tends to follow the split lines.

3-37. HEALING

A wound is healed by the reuniting of the margins. This is accomplished by the growth and multiplication of the cells at the margins of the wound.

3-38. SCARRING

Scars result from the healing process. In some human groups (for example, Orientals), scars can become quite large and are called keloids. For all groups, the scar (cicatrix) is much less prominent for wounds that parallel the split lines.
 
 Lesson 3
SWALLOWING (DEGLUTITION)

6-8. INTRODUCTION

When the food has been adequately broken down (increased surface area), wetted thoroughly, and tested (tasted), it is ready to be swallowed.

a.      The bolus is moved posteriorly out of the mouth (oral cavity) into the pharynx and then down through the esophagus to the stomach.

b.      The pharynx is common to both the digestive and respiratory systems. Therefore, as the bolus passes through the pharynx, both the upper and lower air passageways must be protected. Otherwise, food particles might enter the passageways.

6-9. MOVEMENT OUT OF THE ORAL CAVITY

a.      Initial Movement of the Bolus. There are intrinsic muscles in the tongue. Through their action, the tongue arches upward and presses against the hard palate, the roof of the mouth. This initiates the posterior movement of the bolus.

b.      Action of the Hyoid Complex. The muscles of the hyoid bone pull the hyoid bone upward and force the tongue upward into the oral cavity. This closes up the front part of the oral cavity and forces the bolus further to the rear.

c.      Action of the Soft Palate. As the bolus approaches the pharynx, the soft palate is raised. Thus, the soft palate serves as a trap door to close the upper air passageway. By tensing to resist the pressure from the bolus of food, the soft palate ensures the continued backward movement of the bolus into the pharynx.

6-10. MOVEMENT THROUGH THE PHARYNX

a.      Pharyngeal Constrictor Muscles. The wall of the pharynx contains three pharyngeal constrictor muscles. By wavelike contractions, these muscles force the bolus down into the beginning of the esophagus.

b.      Action of the Epiglottis. As the hyoid bone's muscles raise the tongue up into the oral cavity, they also raise the larynx. The larynx is raised because it is attached to the inferior margin of the hyoid bone. As the larynx is raised, its epiglottis automatically turns down over the opening of the larynx. Thus, food is prevented from entering the lower-air passage-way.

6-11. MOVEMENT THROUGH THE ESOPHAGUS

The esophagus is a tube with muscular walls. It extends from the pharynx above, through the neck and thorax, to the stomach in the abdomen. Wavelike contractions (peristalsis) move the bolus through the esophagus to the stomach.
 
http://classroom.jc-schools.net/basic/scianatomy.html
Serous membranes line body cavities that do not open directly to the outside, and they cover the organs located in those cavities. Serous membranes are covered by a thin layer of serous fluid that is secreted by the epithelium. Serous fluid lubricates the membrane and reduces friction and abrasion when organs in the thoracic or abdominopelvic cavity move against each other or the cavity wall. Serous membranes have special names given according to their location. For example, the serous membrane that lines the thoracic cavity and covers the lungs is called pleura. 




http://en.wikipedia.org/wiki/Serous_membrane

[img[http://upload.wikimedia.org/wikipedia/commons/6/64/Illu_stomach2.jpg]]


Serous membrane
From Wikipedia, the free encyclopedia
• Learn more about citing Wikipedia •Jump to: navigation, search
Serous membrane 
 
Layers of the enteric nervous system. (Serosa at top, in red.) 
 
Stomach. (Serosa is labeled at far right, and is colored yellow.) 
Latin tunica serosa 
Precursor mesoderm 
MeSH Serous+membrane 
Dorlands/Elsevier t_22/12832289 
In anatomy, a serous membrane, or serosa, is a smooth membrane consisting of a thin layer of cells which excrete a fluid, known as serous fluid. Serous membranes line and enclose several body cavities, known as serous cavities, where they secrete a lubricating fluid which reduces friction from muscle movement. Serosa is not to be confused with adventitia, a connective tissue layer which binds together structures rather than reducing friction between them.

Contents [hide]
1 Structure 
2 Serous cavities 
3 Embryological origins 
4 Additional images 
5 External links 
 


[edit] Structure
Each serous membrane is composed of a secretory epithelial layer and a connective tissue layer underneath.

The epithelial layer, known as mesothelium, consists of a single layer of avascular flat nucleated cells (simple squamous epithelium) which produce the lubricating serous fluid. This fluid has a consistency similar to thin mucous. These cells are bound tightly to the underlying connective tissue. 
The connective tissue layer provides the blood vessels and nerves for the overlying secretory cells, and also serves as the binding layer which allows the whole serous membrane to adhere to organs and other structures. 
For the heart, the surrounding serous membranes include:

Outer Inner 
Parietal peritoneum Visceral peritoneum 
Parietal pleura Pulmonary pleura 
Parietal pericardium Visceral pericardium (epicardium) 

Other parts of the body may also have specific names for these structures. For example, the serosa of the uterus is called the perimetrium.


[edit] Serous cavities
 
Highly schematic diagram of an organ invaginating into a serous cavityThe pericardial cavity (containing the heart), pleural cavity (containing the lungs) and peritoneal cavity (containing most organs of the abdomen) are the three serous cavities within the human body. It should be noted that while serous membranes have a lubricative role to play in all three cavities, in the pleural cavity it has a greater role to play in the function of breathing.

The serous cavities are formed from the intraembryonic coelom and are basically an empty space within the body surrounded by serous membrane. Early in embryonic life visceral organs develop adjacent to a cavity and invaginate into the bag-like coelom. Therefore each organ becomes surrounded by serous membrane - they do not lie within the serous cavity. The layer in contact with the organ is known as the visceral layer, while the parietal layer is in contact with the body wall.


[edit] Embryological origins
All serous membranes found in the human body formed ultimately from the mesoderm of the trilaminar embryo. The trilaminar embryo consists of three relatively flat layers of ectoderm, endoderm (also known known as "entoderm") and mesoderm.

As the embryo develops, the mesoderm starts to segment into three main regions: the paraxial mesoderm, the intermediate mesoderm and the lateral plate mesoderm.

The lateral plate mesoderm later splits in half to form two layers bounding a cavity known as the intraembryonic coelom. Collectively, both layers are known as splanchnopleure. Individually, each are known as visceropleure and somatopleure.

The visceropleure is associated with the underlying endoderm which it is in contact with, and later becomes the serous membrane in contact with visceral organs within the body. 
The somatopleure is associated with the overlying ectoderm and later becomes the serous membrane in contact with the body wall. 
The intraembronic coelom can now be seen as a cavity within the body which is covered with serous membrane derived from the splanchnopleure. This cavity is divided and demarcated by the folding and development of the embryo, ultimately forming the serous cavities which house many different organs within the thorax and abdomen.


[edit] Additional images

Layers of stomach wall



 
Section of duodenum of cat. X 60.



 


[edit] External links
MeSH serous+membrane 
serosa at eMedicine Dictionary 
Histology at BU 00102loa - "Tissues, Layers, and Organs: transverse section of rat gut" 
Histology at OU 21_02 - "Uterus" 
Histology at OU 54_07 - "Jejunum" 
UIUC Histology Subject 844 
[hide]v • d • etissue layers 
mesothelium, serosa/adventitia, muscularis externa (outer & inner), submucosa, mucosa (muscularis mucosa, lamina propria, epithelium), lumen 
Q: Why do I shiver when I become cold?

A: When muscles need to create ATP, their only energy source, they combine glucose with oxygen. This reaction also creates heat as a by-product. The body uses this heat to maintain normal body temperature.

When the temperature of the body drops below normal, the brain signals the muscles to contract rapidly—what we perceive as shivering. The heat generated by these rapid muscle contractions helps to raise or at least stabilize body temperature.

When lactic acid builds up in muscle fibers, it increases the acidity in the fibers. Key enzymes in the fibers are then deactivated, and the fibers can no longer function properly. As a result, muscles are not as effective, contracting less and less. This condition is known as muscle fatigue.

In a state of fatigue, muscle contractions may be painful. Finally, muscles may simply stop working.

Lactic acid is normally carried away from muscles by the blood. It is then transported to the liver, where it is changed back into glucose. In order to do this, however, the liver needs ATP. To produce ATP in the liver, oxygen is once again needed. This is why breathing rate remains high even after vigorous physical activity is stopped. Only after the liver produces the necessary ATP does breathing gradually return to normal.
Bob's Anatomy and Physiology Study Page
[img[http://upload.wikimedia.org/wikipedia/commons/8/89/Illu_muscle_structure.jpg]]
 Lesson1
INTRODUCTION

3-1. INTRODUCTION

The envelopes of the body serve to protect the living structures within the body in a number of ways. The envelopes are like an air conditioner; they help to remove heat. The envelopes are like a blanket; they help to retain heat when the surrounding air is cold. One of the envelopes, the skin, is like a chemical factory; it manufactures vitamin D in the presence of sunlight. The skin is like an umbrella; it helps to protect us from the sun and the rain. The skin also protects the body from dehydration and friction.

3-2. ENVELOPES OF THE BODY

The human body has three concentric coverings (Figure 3-1), one inside of the other. The outermost layer is the integument proper (skin). Immediately beneath the skin is the subcutaneous layer. Beneath this layer is the investing deep fascia, a membrane which completely covers the remaining structures of the body.


[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0301.jpg]]
Figure 3-1. The integument and related structures. 

These three concentric layers form complete envelopes around the body, except for the various openings.

3-3. THE INTEGUMENTARY SYSTEM

An organ system is a group of organs performing a common overall function.

The outermost covering of the body is the integument proper, the largest single organ of the body. A number of structures are formed or derived from the various layers of the integument proper. These structures are known as the integumentary derivatives, sometimes referred to as "appendages." Together, the integument proper and the integumentary derivatives make up the integumentary system.
 
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5120471572469334946"><img src="http://lh5.google.com/cardwell.bob/Rw-RxAeFQ6I/AAAAAAAABkk/dtfbmE7jdGE/s400/Facial_Bones.jpg" /></a></html>
<html><embed type="application/x-shockwave-flash" src="http://picasaweb.google.com/s/c/bin/slideshow.swf" width="600" height="400" flashvars="host=picasaweb.google.com&RGB=0x000000&feed=http%3A%2F%2Fpicasaweb.google.com%2Fdata%2Ffeed%2Fapi%2Fuser%2Fcardwell.bob%2Falbumid%2F5118044722673565521%3Fkind%3Dphoto%26alt%3Drss" pluginspage="http://www.macromedia.com/go/getflashplayer"></embed></html>
http://www.geocities.com/doctor_uae/ctb3.htm
http://www.geocities.com/doctor_uae/study.htm
http://www.geocities.com/doctor_uae/anatomy.htm
Before TiddlyWiki supported [[Plugins]], several independent developers created their own extended adaptations to support new features. These can be considered forks of the original core code, and won't necessarily be based on the latest version. For that reason, the trend more recently has been for developers to release new features as [[Plugins]] that can be readily mixed and matched and upgraded to the latest version.

Adaptations include:
* TimoBenk's TiddlyTasks at http://m28s01.vlinux.de/tiddlytasks.html
* KeithHodges' TiddlyPom at http://www.warwick.ac.uk/~tuspam/tiddlypom.html
* RodneyGomes' RoWiki, based on PyTW, at http://rodney.gotdns.com/
* LarsEnglund's TiddlyWikiRDF at http://larsenglund.com/TiddlyWikiRDF/
* BramChen's PrinceTiddlyWiki at http://ptw.sourceforge.net/
* JoshGoebel's ServerSideWiki at http://www.serversidewiki.com
* MasakiYatsu's LesserWiki at http://lesserwiki.org/
* MichaelBridgen's StickyWiki at http://www.squaremobius.net/~mikeb/Darcs/sticky-wiki/
* DavidHarper's BloTid, at http://www.spacecoastweb.net/BloTid/Tiddly/
* JacquesTurbé's TidliPo, in French at http://avm.free.fr/tidlipo.html
* JoeRaii's pytw at http://www.cs.utexas.edu/~joeraii/pytw/ and his Siglet at http://www.cs.utexas.edu/~joeraii/siglet/
* JároliJózsef's MagyarTiddlyWiki at http://innen.hu/MagyarTiddlyWiki in Hungarian
* Yoshimov's EncryptedTiddlyWiki, at http://wiki.yoshimov.com/?page=EncryptedTiddlyWiki
* TiagoDionizio's TsWiki using Tcl and SQLite, at http://mega.ist.utl.pt/~tngd/wiki/
* TimMorgan's ZiddlyWiki based on Zope, at http://ziddlywiki.org/
* SteveRumsby's YetAnotherTiddlyWikiAdaptation at http://www.rumsby.org/yatwa/
* PhonoHawk's PerlTiddlyWiki at http://ccm.sherry.jp/tiddly/
* NathanBower's GTDTiddlyWiki at http://shared.snapgrid.com/gtd_tiddlywiki.html
* GeetDuggal's PileTiddly at http://www.geetduggal.com/PileTiddly/
* DanPhiffer's TiddlyWikiRemote at http://phiffer.org/tiddly/
* JonnyLeRoy's TiddlyTagWiki at http://www.digitaldimsum.co.uk/
* JodyFoo's TagglyWiki at http://informationality.com/tagglywiki/tagglywiki.html
* ChristianHauck's at http://www.christianhauck.net/html/14300.html
* TonyLownds's TiddlyHacks at http://tony.lownds.com/tiddly/dev/cgi/index.cgi
* AlanHecht's QwikiWeb at http://snipurl.com/qwikiweb
* TimCuthbertson and MattGiuca's TiddlyWikiCSS at http://codestar.lidonet.net/misc/tiddlywikicss.html
** PeterLazarev's further improvements at http://petka.webhop.net/#NiceTiddlyWiki
* PatrickCurry and GabrielJeffrey's PhpTiddlyWiki at http://www.patrickcurry.com/tiddly/

* There's also KevemBuangga's TiddlyWikiClone at http://www.kevembuangga.com/hwk/hailiwiki.htm
* Also inspired by TiddlyWiki, Dr MichaelRees' [[DotWikIE|http://comet.it.bond.edu.au/dotsoft/Pages/dotwikiehome.aspx]],
* And AndreNho's StickWiki at http://stickwiki.sourceforge.net/

See also the earlier FirstVersionAdaptations and SecondVersionAdaptations. There's also some TiddlyWikiTools that extend TiddlyWiki.
Spasm
From Wikipedia, the free encyclopedia
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Name of Symptom/Sign:
Muscle spasm
Classifications and external resources ICD-10 R25.2 
ICD-9 728.85 
A spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice. It is sometimes accompanied by a sudden burst of pain, but is usually harmless and ceases after a few minutes. Spasmodic muscle contraction may also be due to a large number of medical conditions, however, including the dystonias.

By extension, a spasm is also a sudden and temporary burst of energy, activity, or emotion.

 
Muscle spasms in a patient suffering from tetanus (1809)A subtype of spasms is colic, an episodic pain due to spasms of smooth muscle in a particular organ (e.g. the bile duct). A characteristic of colic is the sensation of having to move about, and the pain may induce nausea or vomiting if severe. Series of spasms or permanent spasms are called a spasmism.

In very severe cases, the spasm can induce muscular contractions that are more forceful than the sufferer could generate under normal circumstances. This can lead to torn tendons and ligaments.

Some argue that hysterical strength is a type of spasm induced by the brain under extreme circumstances.

Cramp 
Angina 
Cadaveric spasm 
Myoclonus 
Hypnic jerk 
Blepharospasm 
Muscle contraction 
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5125488905173904258"><img src="http://lh6.google.com/cardwell.bob/RyFlANUYq4I/AAAAAAAABys/maKsqbYETu0/s800/meninges.gif.jpg" /></a></html>
Spleen
The spleen is really part of the circulatory system, but it's always described with the lymphatic organs because of the very large population of lymphocytes found in it. The spleen is a flaccid bag that serves as a storage site for blood, a processing station for the scavenging of aged erythrocytes, and a few other things. It's one of the "dispensable" organs, because mammals get along quite nicely without a spleen. In the case of a traumatic injury that ruptures the spleen, the easiest thing to do is to take it out, and a splenectomy is commonly done. It's easier to remove the spleen than to try to repair it and risk renewed hemorrhage.
Steps in mitosis 

interphase - the stage where a cell grows in size and performs all normal cell activities 

prophase - nuclear membrane disappears, chromatids become visible, centrioles start to migrate, spindle fibers start to form 

metaphase - chromatids align along the equator, centrioles are at the poles 

anaphase - chromatids are pulled apart by spindle fibers and start to move towards the poles 

telophase - chromosomes are each pole, nuclear membrane reforms and the cell starts to "pinch in" 

Cytokinesis now occurs and divides the cytoplasm creating two new genetically identical cells 


FUNCTIONAL CLASSIFICATION Joints are class. Depending on the degree of mobility they allow.

1. Synarthrosis: Permints little or no mobility.Most of these joints are fibrous and can be categorized as to how the two bones are joined together. a) SYNCONDROSES : Two bones are connected by a piece of cartilage. b) SYNOSTOSES: the two bones are initially separated 
<html><a href="http://picasaweb.google.com/cardwell.bob/AnatomyPhotos/photo#5119523359654494466"><img src="http://lh5.google.com/cardwell.bob/RwwzXweFQQI/AAAAAAAABaA/QdMzk35zv8M/s400/joints.gif.jpg" /></a></html>
'Synovial Membranes' or Synovium

http://en.wikipedia.org/wiki/Synovial_membrane

Synovium
From Wikipedia, the free encyclopedia
(Redirected from Synovial membrane)• Ten things you didn't know about images on Wikipedia •Jump to: navigation, search
Synovium is the soft tissue that lines the non-cartilaginous surfaces within joints with cavities (synovial joints). The word synovium comes from a Latin word meaning "with egg," because the synovial fluid in joints that have a cavity between the bearing surfaces is like egg white.

Contents [hide]
1 Structure 
2 Mechanics 
3 Pathology 
4 References 
 


[edit] Structure
 
Black is subintima, purple is intima, light brown is bone, orange is cartilage, yellow is synovial fluidSynovium is very variable but often has two layers. The outer layer, or subintima, can be of almost any type: fibrous, fatty or loosely "areolar". The inner layer, or intima, consists of a sheet of cells thinner than a piece of paper. Where the underlying subintima is loose the intima sits on a pliable membrane, giving rise to the term synovial membrane. This membrane, together with the cells of the intima, provides something like an inner tube, sealing the synovial fluid from the surrounding tissue (effectively stopping the joints being squeezed dry when subject to impact, such as running). The intimal cells are of two types, fibroblasts and macrophages, both of which are different in certain respects from similar cells in other tissues. The fibroblasts manufacture a long chain sugar polymer called hyaluronan, which is what makes the synovial fluid "ropy" like egg-white, together with a molecule called lubricin, which lubricates the joint surfaces. The water of synovial fluid is not secreted as such, but is effectively trapped in the joint space by the hyaluronan. The macrophages are responsible for the removal of undesirable substances from the synovial fluid. The surface of synovium may be flat or may be covered with finger-like projections or villi, which probably help to allow the soft tissue to change shape as the joint surfaces move one on another. Just beneath the intima most synovium has a dense net of small blood vessels which provide nutrients not only for synovium, but also for the avascular cartilage. In any one position much of the cartilage is close enough to get nutrition direct from synovium. Some areas of cartilage have to obtain nutrients indirectly and may do so either from diffusion through cartilage or possibly by 'stirring' of synovial fluid, although the film is very thin.


[edit] Mechanics
Although a biological joint can resemble a man-made joint in being a hinge or a ball and socket, the engineering problems that nature must solve are very different because the joint works within an almost completely solid structure, with no wheels or nuts and bolts. In general the bearing surfaces of man made joints interlock, as in a hinge. This is rare for biological joints, although the badger's jaw interlocks. More often the surfaces are held together by cord-like ligaments. Virtually all the space between muscles, ligaments, bones and cartilage is filled with pliable solid tissue. The fluid-filled gap is mostly only a twentieth of a millimetre thick. This means that synovium has certain rather unexpected jobs to do. These may include:

Providing a plane of separation, or disconnection, between solid tissues so that movement can occur with minimum bending of solid components. If this separation is lost, as in a 'frozen shoulder' the joint cannot move. 
Providing a packing that can change shape in whatever way is needed to allow the bearing surfaces to move on each other. 
Controlling the volume of fluid in the cavity so that it is just enough to allow the solid components to move over each other freely. This volume is normally so small that the joint is under slight suction. 

[edit] Pathology
Synovium can become irritated and thickened in conditions such as rheumatoid arthritis. When this happens, the synovium can become a danger to the bearing surface structure in a variety of ways. Excess synovial fluid weeping from inflamed synovium can provide a barrier to diffusion of nutrients to cartilage. The synovial cells may also use up nutrients so that the glucose level in the tissue is almost zero. These factors may lead to starvation and death of cartilage cells. Synovial cells may also produce enzymes which can digest the cartilage surface, although it is not clear that these will damage cartilage with healthy cells.


[edit] References
Edwards, JCW. The Synovium. In 'Rheumatology', editors Hochberg MC et al, Mosby (an imprint of Elsevier), Edinburgh, 2003, chapter 17, pp 159-168. 
Retrieved from "http://en.wikipedia.org/wiki/Synovium"
Category: Tissues
http://en.wikipedia.org/wiki/Synovial_membrane
Synovium
From Wikipedia, the free encyclopedia
(Redirected from Synovial membrane)• Ten things you didn't know about images on Wikipedia •Jump to: navigation, search
Synovium is the soft tissue that lines the non-cartilaginous surfaces within joints with cavities (synovial joints). The word synovium comes from a Latin word meaning "with egg," because the synovial fluid in joints that have a cavity between the bearing surfaces is like egg white.

Contents [hide]
1 Structure 
2 Mechanics 
3 Pathology 
4 References 
 


[edit] Structure
 
Black is subintima, purple is intima, light brown is bone, orange is cartilage, yellow is synovial fluidSynovium is very variable but often has two layers. The outer layer, or subintima, can be of almost any type: fibrous, fatty or loosely "areolar". The inner layer, or intima, consists of a sheet of cells thinner than a piece of paper. Where the underlying subintima is loose the intima sits on a pliable membrane, giving rise to the term synovial membrane. This membrane, together with the cells of the intima, provides something like an inner tube, sealing the synovial fluid from the surrounding tissue (effectively stopping the joints being squeezed dry when subject to impact, such as running). The intimal cells are of two types, fibroblasts and macrophages, both of which are different in certain respects from similar cells in other tissues. The fibroblasts manufacture a long chain sugar polymer called hyaluronan, which is what makes the synovial fluid "ropy" like egg-white, together with a molecule called lubricin, which lubricates the joint surfaces. The water of synovial fluid is not secreted as such, but is effectively trapped in the joint space by the hyaluronan. The macrophages are responsible for the removal of undesirable substances from the synovial fluid. The surface of synovium may be flat or may be covered with finger-like projections or villi, which probably help to allow the soft tissue to change shape as the joint surfaces move one on another. Just beneath the intima most synovium has a dense net of small blood vessels which provide nutrients not only for synovium, but also for the avascular cartilage. In any one position much of the cartilage is close enough to get nutrition direct from synovium. Some areas of cartilage have to obtain nutrients indirectly and may do so either from diffusion through cartilage or possibly by 'stirring' of synovial fluid, although the film is very thin.


[edit] Mechanics
Although a biological joint can resemble a man-made joint in being a hinge or a ball and socket, the engineering problems that nature must solve are very different because the joint works within an almost completely solid structure, with no wheels or nuts and bolts. In general the bearing surfaces of man made joints interlock, as in a hinge. This is rare for biological joints, although the badger's jaw interlocks. More often the surfaces are held together by cord-like ligaments. Virtually all the space between muscles, ligaments, bones and cartilage is filled with pliable solid tissue. The fluid-filled gap is mostly only a twentieth of a millimetre thick. This means that synovium has certain rather unexpected jobs to do. These may include:

Providing a plane of separation, or disconnection, between solid tissues so that movement can occur with minimum bending of solid components. If this separation is lost, as in a 'frozen shoulder' the joint cannot move. 
Providing a packing that can change shape in whatever way is needed to allow the bearing surfaces to move on each other. 
Controlling the volume of fluid in the cavity so that it is just enough to allow the solid components to move over each other freely. This volume is normally so small that the joint is under slight suction. 

[edit] Pathology
Synovium can become irritated and thickened in conditions such as rheumatoid arthritis. When this happens, the synovium can become a danger to the bearing surface structure in a variety of ways. Excess synovial fluid weeping from inflamed synovium can provide a barrier to diffusion of nutrients to cartilage. The synovial cells may also use up nutrients so that the glucose level in the tissue is almost zero. These factors may lead to starvation and death of cartilage cells. Synovial cells may also produce enzymes which can digest the cartilage surface, although it is not clear that these will damage cartilage with healthy cells.


[edit] References
Edwards, JCW. The Synovium. In 'Rheumatology', editors Hochberg MC et al, Mosby (an imprint of Elsevier), Edinburgh, 2003, chapter 17, pp 159-168. 
Retrieved from "http://en.wikipedia.org/wiki/Synovium"
Category: Tissues
 Lesson 7
TEMPERATURE CONTROL BY MEANS OF THE BLOOD

10-38. ELIMINATION OF EXCESS HEAT

Heat is produced as a by-product by various activities of the human body, particularly muscular contractions. When excess heat is accumulated, it must be eliminated from the body to maintain a healthy condition. 

The water of the blood has a great heat-carrying capacity. 
There are superficial capillary beds in the subcutaneous layer, close to the surface of the body. When the blood flows through these beds, some of its heat can radiate directly to the surrounding environment. 
The sweat glands take water from the blood and secrete it onto the surface of the skin. Here, even more calories of heat are lost during the evaporation of the water. 
10-39. CONSERVATION OF BODY HEAT

On the other hand, if the body has an insufficient amount of heat, heat loss must be reduced. For this purpose, the superficial capillary beds can be closed down. Then, the fat in the subcutaneous layer serves as insulation.

10-40. CORE TEMPERATURE CONTROL

Unlike the peripheral portions of the body, whose temperatures may vary considerably, the center of the body must be maintained at a certain temperature within very narrow limits. 

Control. There are special temperature detectors in the hypothalamus of the forebrainstem. These continuously monitor the temperature of the blood flowing through the brain. 
Counter-Current Mechanism. The peripheral blood in the limbs is several degrees cooler than the blood in the center of the body. Therefore, it must be warmed as it returns toward the heart. As previously described, the arteries and veins of the limbs are located side by side as they extend from the trunk and through the length of the limbs. As it returns to the trunk, cool venous blood is gradually warmed by the arterial blood flowing in the opposite direction. 
10-41. COOLING OF ORGANS WITH A HIGH METABOLIC RATE

Certain organs of the body, such as the brain and the liver, have a relatively high metabolic rate. Because of this, they produce excessive heat. Part of the blood supply to these organs is specifically designed to remove the excess calories of heat.

10-42. WARMING OF INFLOWING AIR

As blood flows through the arteries of the mucoperiosteum of the nasal chambers, the inflowing air is warmed.

10-43. ERYTHEMA

At the site of an infection or injury, the most common reaction observed is redness (erythema). This indicates that extra blood and heat are available for healing.
 
 Lesson 4
TEMPORARY STORAGE

6-12. INTRODUCTION

a.      The stomach is a saclike enlargement of the digestive tract. By way of the esophagus, the stomach receives the food that has been processed in the oral cavity.

b.      The stomach's capacity is great enough to allow the individual to take in enough food material at one time to last for an extended period of time. This allows the individual to engage in activities other than eating.

c.      In addition, certain digestive processes are initiated in the stomach.

d.      The food is retained in the stomach for varying lengths of time, depending upon the types of food eaten, the condition of the individual, and many other factors.

6-13. ADAPTATIONS OF THE STOMACH FOR THE STORAGE FUNCTION 

The stomach is adapted as a storage area in several ways.

a. Its wall is quite stretchable. The mucosal lining of the stomach is thrown up into longitudinal folds called rugae. These rugae flatten out as the stomach capacity increases.

b. At each end of the stomach, there is a structure to keep the contents from leaving the stomach.

(1)     At the point where the esophagus enters the stomach, there is a "gastroesophageal valve." This valve appears to be functional, although it has not been demonstrated anatomically. 
(2)     At the other end of the stomach is the well-developed pyloric valve. 
6-14. ADAPTATIONS OF THE STOMACH FOR ADDITIONAL FOOD PROCESSING

a.      Gastric Glands. The mucosal lining of the stomach contains a number of gastric glands. These gastric glands produce gastric digestive juices for initiating digestion, particularly of proteins. Some of the gastric glands also produce hydrochloric acid. Thus, chyme, the mixture produced by the stomach, is quite acid.

b.      Additional Musculature. A third inner, oblique layer of muscle has been added to the stomach wall. With the three layers of muscles, the contents of the stomach are thoroughly mixed.
 
 Lesson 8
THE "RESPIRATORY TREE" AND PULMONARY ALVEOLI

7-30. INTRODUCTION

The infralaryngeal structures (Figure 7-4) include the "respiratory tree" and the lungs. The respiratory tree is so named because it has the appearance of an inverted tree, with its trunk and branches. It is essentially a tubular structure connecting the larynx to the alveoli of the lungs. This tubular structure is lined with a ciliated epithelium. (Remember, cilia are hair-like projections from cells.) The tubes are kept open (patent) by a series of ring-like structures of cartilage.

7-31. TRACHEA

The "trunk" of the tree is the trachea. The trachea extends from the inferior margin of the larynx, down through the neck, and into the center of the thorax.



Figure 7-4. Infralaryngeal structures.

7-32. BRONCHI

In the center of the thorax, the trachea divides into right and left primary bronchi. The right is somewhat more vertical than the left. Therefore, when a person accidentally aspirates ("breathes in") a foreign object, it is more likely to be found in the right primary bronchus than the left. 

Each primary bronchus extends laterally into the substance of the appropriate lung. Within each lung, the tubular structure divides, subdivides, and divides again, up to about 30 times. Thus, the tubes become more and more numerous and smaller and smaller in size. At the terminals of the branching tubes are groups of spherical alveoli. This gives the appearance of a bunch of grapes. 
A variety of situations may occlude (close or shut off) these tubular air passageways. 
(1)     A foreign object may be aspirated ("breathed in"). 
(2)     The wall of the tube may constrict in a bronchial spasm. 
(3)     The lining of the tube may become swollen with fluid and close the passageway. 
7-33. "DEAD AIR"

None of the air found in the upper and lower passageways plays a part in actual respiration. Thus, this air is often referred to as "dead air." During quiet breathing, it amounts to about two-fifths of the total air volume exchanged.

7-34. PULMONARY ALVEOLI

External respiration is the exchange of gases between the air and the blood. External respiration takes place in the alveoli (alveolus, singular). The alveoli are small, spherical sacs that are continuous with the terminal elements of the branches of the respiratory tree. As we indicated earlier, external respiration is a surface phenomenon in which the gases pass through the wall of the alveolus. 

Since there is a critical relationship between volume and surface area, the inflated alveolus is spherical. The alveolus is also of a particular size that is ideal for the efficiency of external respiration. 
In each lung, there are billions of alveoli. 
Numerous blood capillaries are adjacent to the walls of the alveoli. 
To facilitate the exchange of gases between the air in the alveolus and the blood in the capillaries, the wall of the alveolus contains a special chemical known as surfactant. 
The inner surfaces of the alveoli must be kept wet to make the transfer of gases possible. Because these surfaces are wet, one of the major fluid losses of the body is with the exhaled air. 
 
Lesson 6
THE ADRENAL (SUPRARENAL)GLANDS

11-13. LOCATION AND STRUCTURE

As seen in a previous lesson, the kidneys are attached to the upper posterior abdominal wall by a combination of fat and fascia. The adrenal (suprarenal) gland is embedded in the fat immediately above each kidney. Each is triangular or crescent shaped. Each adrenal gland has a central medulla and an outer cortex.

11-14. HORMONES OF THE ADRENAL MEDULLA

The central portion of the adrenal gland produces two hormones: epinephrine (Adrenalin) and norepinephrine (noradrenalin). These hormones mobilize the energy-producing organs of the body and immobilize the others. This is important during the stress reaction ("fight or flight").

11-15. HORMONES OF THE ADRENAL CORTEX

The outer portion (the cortex) of the adrenal gland produces a variety of hormones which can be grouped into three categories: 

Mineralocorticoids (for example, aldosterone), which are concerned with the electrolyte and water balance of the body. 
Glucocorticoids (for example, cortisol), which are concerned with many metabolic functions. They are especially known for their anti-inflammatory effects. 
Sex Hormones (adrenal androgens and estrogens). 
 Lesson 10
THE APPENDICULAR SKELETON

4-36. INTRODUCTION

The appendicular skeleton consists of the bones of the upper and lower members.

4-37. THE GIRDLES

Each member is attached ("appended") to the axial skeleton by a skeletal element called a girdle.

a.      Pelvic Girdles. The girdle of each lower member is called the pelvic girdle. Each pelvic girdle is attached firmly to the corresponding side of the sacrum. With their ligaments, the two pelvic girdles and sacrum together form a solid bony circle known as the bony pelvis.

b.      Pectoral Girdles. The girdle of each upper member is called the pectoral girdle. Unlike the pelvic girdles, each pectoral girdle is very loosely attached to the axial skeleton. The sole attachment is by the sternoclavicular joint, which in turn is constructed to increase the degrees of motion.

4-38. GENERAL STRUCTURE OF THE LIMBS

Both the upper and lower members have limbs arranged in three segments. The proximal segment has one bone. The middle segment has two bones. The distal segment has many bones arranged in a five-rayed (pentadactyl) pattern.

4-39. FUNCTIONS OF THE LOWER MEMBER

a.      Body Support. The skeleton of the lower member is strongly constructed in a columnar fashion for body support. The foot at the lower end of the lower limb extends at a 90° angle. Therefore, the foot forms a base for the body during the erect, standing posture.

b.      Locomotion. At the same time, the lower limb has a series of linkages that enable the body to move from place to place.

4-40. FUNCTIONS OF THE UPPER MEMBER

The grasping hand is the distal segment of the upper member. The flexible construction of the pectoral girdle and the bones of the upper limb serve to place the grasping hand into as many positions as possible. This is particularly helpful in grasping food and placing it into the mouth. The grasping hand also serves as a tool-holding device. (When we study the nervous system, we shall see that a significant portion of the brain and special pathways are present in order to control the movements of this grasping hand.)
 
 Lesson 4
THE AUTONOMIC NERVOUS SYSTEM

12-10. CONTROL OF VISCERAL ACTIVITIES

The autonomic nervous system (ANS) is that portion of the nervous system concerned with commands for smooth muscle tissue, cardiac muscle tissue, and glands. 

The term visceral organs may be used to include: 
(1)  The various hollow organs of the body whose walls have smooth muscle tissue in them. Examples are the blood vessels and the gut. 
(2) The glands. 
The visceral organs are innervated by the ANS. This results in a "visceral motor system." For most of us, the control of the visceral organs is automatic, that is, without conscious control. However, recent research demonstrates that conscious control of some of the visceral organs is possible after proper training. 
12-11. TWO MAJOR SUBDIVISIONS

The ANS is organized into two major subdivisions--the sympathetic and the parasympathetic nervous systems. 

The neurons of the sympathetic nervous system originate in the thoracic and lumbar regions of the spinal cord. Thus, it is also known as the thoraco-lumbar outflow. 
Some of the neurons of the parasympathetic nervous system originate in nuclei of the brainstem. Others originate in the sacral region of the spinal cord. Thus, the parasympathetic nervous system is also known as the cranio-sacral outflow. 
In the ANS, there are always two neurons (one after the other) connecting the CNS with the visceral organ. The cell bodies of the second neurons form a collection outside the CNS, called a ganglion. Processes of these postganglionic neurons extend to the visceral organs. Those processes going to peripheral visceral organs are included with the peripheral nerves. 
12-12. EQUILIBRIUM

Under ordinary circumstances, the sympathetic and parasympathetic nervous system have opposite effects upon any given visceral organ. That is, one system will stimulate the organ to action, and the other system will inhibit it. The interplay of these two systems helps visceral organs to function within a stable equilibrium. This tendency to produce an equilibrium is called homeostasis.

12-13. RESPONSE TO STRESS

Under conditions of stress, the sympathetic nervous system produces a "fight-or-flight" response. In other words, it mobilizes all of the energy producing structures of the body. Simultaneously, it inhibits those structures that do not contribute to the mobilization of energy. For example, the sympathetic nervous system makes the heart beat faster. Later, as equilibrium is restored, the parasympathetic nervous system slows the heart down.
 
Lesson 3
THE BLOOD VESSELS-THE CONDUITS OF THE CARDIOVASCULAR SYSTEM

10-18. INTRODUCTION

The blood vessels are tubular structures throughout the entire body. Since this tubular system is continuous (without interruption or opening), we sometimes refer to it as a closed system.

10-19. TYPES OF BLOOD VESSELS AND THEIR CONSTRUCTION

In general, there are three types of blood vessels--arteries, veins, and capillaries. We use the following abbreviations:

A. = artery   V. = vein 
Aa. = arteries  Vv. = veins 
NAVL = nerve(s), artery(ies), vein(s), lymphatic(s) 
Three General Layers. In general, a blood vessels has a wall composed of three layers. 
(1)  Intima. The innermost layer is the intima. The intima is a simple epithelium made up of a single layer of flat epithelial cells. 
(2)  Media. The main portion of the wall is the media. It is made up of a combination of FCT and smooth muscle tissue. 
(3)  Adventitia. The outer surface of the blood vessel is the adventitia. It is an FCT layer. 
Comparison of the Structures of Arteries and Veins. Given an artery and a vein with similar inner diameters, the artery will have a thicker wall than the vein. This greater thickness is due to the presence of more smooth muscle tissue and the presence of elastic FCT as a significant element. 
Capillary Structure. Capillary walls have only one layer--the intima. Capillary networks (beds) are the exchange areas for the cardiovascular system. This includes the internal exchange areas between the blood and the individual cells of the body. Since the capillary wall consists of flat single cells, substances can move readily between the body cells and the blood. 
10-20. SPECIAL SITUATIONS

This paragraph describes several special situations associated with the blood vascular system. 

Nutrient Versus Functional Blood Supplies. The lungs, liver, and heart actually have two blood supplies. The functional blood supply provides blood to be worked upon by the organ. The nutrient blood supply provides blood for the usual exchange of materials between body cells and the blood. 
Collateral Circulation. A collateral circulation is a special organization of blood vessels around a major joint of other area of the body. Its purpose is to provide a continuing supply of blood even if one of the vessels is damaged. Several blood vessels are included so that there will be an alternate route when needed. 
End Arteries. There are other areas of the body where a single artery is the sole supply of blood. Such an artery is called an end artery. When an end artery is damaged and can no longer supply blood to an area, the tissues of the areas will die. End arteries are most common in the brain and the heart. 
Portal Veins. A portal vein is a venous blood vessel that begins with capillaries in one area and ends in capillaries of another area. The most important portal vein in the human body is the hepatic portal vein. The hepatic portal vein extends from the capillaries of the digestive system to the capillaries/sinusoids of the liver. 
10-21. LOCATIONS OF BLOOD VESSELS TYPES

In the human body, blood vessels are located differently according to their types. 

Arteries. If an artery is injured, the threat to life is greater than with other types of blood vessels. For protection, arteries tend to be located deep within the structures of the body. Only the very smallest of arteries, especially the cutaneous arteries, come close to the surface of the body. 
Veins. There are both deep veins and cutaneous veins. The deep veins accompany the arteries side by side. The cutaneous veins are found in the subcutaneous layer of the body. The cutaneous veins drain into the deep veins at specific locations (especially the inguinal region and the axillary region). 
Capillaries. The capillaries are located throughout all tissues of the body. No individual cell is more than two cells away from a capillary. The networks of capillaries in the tissues are often called capillary beds. 
10-22. PATTERNS OF BLOOD CIRCULATION

Blood vessels make up a closed system, since there is no place in the system where whole blood can leave. 

Direction of Flow of Arteries and Veins. Arteries carry blood from the chambers of the heart to the tissue of the body. Veins carry blood from the tissues to the chambers of the heart. (Coronary arteries carry blood from the chambers of the heart inside to the walls of the heart outside.) 
wo-Cycle System. It is also a two-cycle system (Figure 10-2). It involves both the pulmonary cycle and the systemic cycle. Blood circulates through two circuits. In the pulmonary cycle, blood circulates from the heart to the lungs and back to the heart. In the systemic cycle, blood circulates from the heart to the rest of the body and back to the heart. 

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1002.jpg]]

Figure 10-2. Cardiovascular circulatory pattern.

c. Fetal Circulation. Since the fetus is located within the uterus, its lungs do not take in air. Therefore, the pulmonary cycle does not function in the fetus. Essentially, fetal blood flows to and from the placenta. There are certain bypasses in the heart to avoid the pulmonary cycle. At the time of birth, the fetal circulation is changed to the normal pattern.
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Lesson 2
THE CENTRAL NERVOUS SYSTEM

12-5. INTRODUCTION

a. Centrality. The central nervous system (CNS) (Figure 12-2) is central in both location and function.



Figure 12-2. The human central nervous system (CNS).

b. Major Subdivisions. The fully formed CNS can be considered in two major subdivisions: the brain and the spinal cord.

12-6. THE HUMAN BRAIN

The human brain (Figures 12-3 and 12-4) has three major subdivisions: brainstem, cerebellum, and cerebrum. 

The Brainstem. The brainstem is the core of the brain. We consider it in three parts--the hindbrainstem, the midbrainstem, and the forebrainstem. In general, the brainstem is made up of many nuclei and fiber tracts. It is a primary coordinating center of the human nervous system. 
The Cerebellum. Over the hindbrainstem is the cerebellum. The cerebellum is connected to both the midbrainstem and the hindbrainstem. The cerebellum is the primary coordinating center for muscle actions. Here, patterns of movements are properly integrated. Thus, information is sent to the appropriate muscles in the appropriate sequences. Also, the cerebellum is very much involved in the postural equilibrium of the body. 


Figure 12-3. Human brain; sideview.



Figure 12-4. Human brain; bottom view. 

The Cerebrum. Attached to the forebrainstem are the two cerebral hemispheres (Figure 12-5). Together, these two hemispheres make up the cerebrum. Among related species, the cerebrum is the newest development of the brain. 
(1)  Cerebral hemispheres. The cerebrum consists of two cerebral hemispheres, right and left. They are joined together by a very large fiber tract known as the corpus callosum (the great commissure). 
(2)  Lobes. Each hemisphere can be divided into four lobes. Each lobe is named after the cranial bone it lies beneath--parietal, frontal, occipital, and temporal. (Actually, there are five lobes. The fifth is hidden at the bottom of the lateral fissure. It is known as the insula or insular lobe. It is devoted mainly to visceral activities.) 
(3)  Gyri and sulci. The cerebral cortex, the thin layer at the surface of each hemisphere, is folded. This helps to increase the amount of area available to neurons. Each fold is called a gyrus. Each groove between two gyri is called a sulcus. 
(a) The lateral sulcus is a cleft separating the frontal and parietal lobes from the temporal and occipital lobes. Therefore, the lateral sulcus runs along the lateral surface of each hemisphere. 
(b)   The central sulcus is a cleft separating the frontal from the parietal lobe. Roughly, each central sulcus runs from the left or right side of the cerebrum to top center and over into the medial side of the cerebrum. 
(c)   There are two gyri that run parallel to the central sulcus. Anterior to the central sulcus is the precentral gyrus. Posterior to the central sulcus is the postcentral gyrus. 


Figure 12-5. Left cerebral hemisphere.

12-7. THE HUMAN SPINAL CORD

Extending inferiorly from the brain is the spinal cord (Figure 12-6).



Figure 12-6. A cross section of the spinal cord. 

The spinal cord is continuous with the brainstem. Together, the spinal cord and the brainstem are called the neuraxis. The foramen magnum is taken as the point that divides the brainstem from the spinal cord. Thus, the brainstem is within the cranial cavity of the skull, and the spinal cord is within the vertebral (spinal) canal of the vertebral column. 
The spinal cord has a central portion known as the gray matter. The gray matter is surrounded by the white matter. 
(1)  The gray matter is made up of the cell bodies of many different kinds of neurons. 
(2)  The white matter is made up of the processes of neurons. The white color is due to their myelin sheaths. These processes serve several purposes: Many make a variety of connections within the spinal cord. Many ascend the neuraxis to carry information to the brain. Many descend the neuraxis to carry commands from the brain. 
Lesson 6
THE GENERAL REFLEX AND THE REFLEX ARC

12-20. THE GENERAL REFLEX

The simplest reaction of the human nervous system is the reflex. A reflex is defined as an automatic reaction to a stimulus.

12-21. THE GENERAL REFLEX ARC

The pathway followed by the stimulus (impulse) from beginning to end is the reflex arc. The general reflex arc (Figure 12-10) of the human nervous system has a minimum of five components:



Figure 12-10. The general reflex arc. 

The stimulus is received by a receptor organ specific to that stimulus. 
From the receptor organ, the stimulus is carried to the CNS by way of an afferent (sensory) neuron within the appropriate peripheral nerve. The cell body of this afferent neuron is located in the posterior root ganglion of a spinal nerve or the individual ganglion of a cranial nerve. 
Within the spinal cord or brainstem, the terminal of the afferent neuron synapses with the interneuron, or internuncial neuron. 
INTER = between 
NUNCIA = messenger 

In turn, the internuncial neuron synapses with the cell body of the efferent (motor) neuron.

In the spinal cord, the cell bodies of the efferent (motor) neurons make up the anterior column of the gray matter. In the brainstem, the motor neurons make up the individual nuclei of the cranial nerves. The axon of the motor neuron passes out of the CNS by way of the appropriate peripheral nerve. Command information is thus carried away from the CNS. 
The information is then delivered by the motor neuron to the effector organ. Somatic motor neurons lead to striated muscle fibers, particularly in skeletal muscles. Autonomic (visceral) motor neurons lead to smooth muscle tissue, cardiac muscle tissue, or glands. 

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1210.jpg]]
 Lesson 7
THE GONADS AS ENDOCRINE GLANDS 11-16. GENERAL

We have already seen that the primary sex organs (gonads) produce sex hormones in addition to sex cells (gametes). These hormones help to determine an individual's actual sex (male or female) and promote the sexual development of the individual.

11-17. MALE SEX HORMONES

In the male, certain cells of the testes produce the male sex hormones, known as androgens (for example, testosterone). Androgens are concerned with male sexuality.

11-18. FEMALE SEX HORMONES

The sex hormones of the female are known as the estrogens and progesterone. In the female, these hormones are secreted in a cyclic sequence, the menstrual cycle. During this cycle, the hormones affect a number of tissues of the female body. These tissues include the endometrium of the uterus, the milk-producing portions of the mammary glands, and so forth. During pregnancy, the placenta continues the production of progesterone.
 
Lesson 4
THE HEART-THE PRIMARY MOTIVE FORCE OF THE CARDIOVASCULAR SYSTEM
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1003.jpg]]

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1003.jpg]]

10-23. INTRODUCTION

In humans, the heart is the primary motive force for driving the blood along the arterial vessels. The heart consists of four separate chambers. Two chambers function as a "right heart," and two function as a "left heart." The muscular walls (myocardium) of the chambers apply force to the blood within and force the blood to move out of the chambers. (See Figure 10-3.)

10-24. CHAMBERS OF THE HUMAN HEART 

Atria. Two chambers are called the atria (singular: atrium). Down the middle, an interatrial septum separates the two atria. 
(1)  The muscular walls of the atria tend to be relatively thin. 
(2)  Attached to each atrium is an earlike appendage called an auricle. The auricles of the atria tend to have somewhat thicker walls. 
Ventricles. The other two chambers are the right and left ventricles. Between the ventricles is the interventricular septum. 
(1)  The left ventricle tends to be cylindrical in shape. It has a relatively thick wall. 
(2)  The right ventricle has a somewhat semilunar (half-moon) cross section, since it is wrapped around one side of the left ventricle. 


Figure 10-3. The human heart function.

10-25. FIBROUS SKELETON OF THE HEART

There is an FCT structure within the substance of the heart. This structure is known as the fibrous skeleton of the heart. This fibrous skeleton serves two general purposes: (1) as sites of attachment for muscle tissues and (2) as supporting structures for the cardia valves. All of the fibrous structures are continuous and form the fibrous skeleton of the heart. 

Fibrous Portion of the Interventricular Septum. The uppermost portion (also called the membranous portion) of the interventricular septum is a part of the fibrous skeleton of the heart. 
Atrioventricular (AV) Rings. Each atrioventricular valve of the heart is surrounded by a dense fibrous ring. This ring maintains the valve opening. 
Cylinders at Bases of Great Arteries. Each of the semilunar valves of the heart is located within a short fibrous cylinder. This cylinder maintains the structure and function of the valve. 
10-26. WALL STRUCTURE

The walls of the chambers of the heart are in three layers. 

The chambers themselves are lined with a simple epithelium known as the endocardium. 
Likewise, a simple epithelium surrounds the outside of the heart. It is known as the epicardium. The epicardium is the same as the visceral pericardium, which we shall discuss later. 
By far the most important is the myocardium, the middle layer. It is made up of cardiac muscle tissue. 
(1)  Cardiac muscle tissue consists of fibers formed by the fusion of many individual cells (syncytium). These cardiac fibers are striated and branched. 
(2)  The myocardium is thicker in the walls of the ventricles than the atria. This is because greater pressures are needed for the ventricles to perform their function. The wall of the left ventricle is especially thick, since it has to drive the blood throughout the body. 
(3)  The inner surfaces of the ventricular walls have ridges of muscle known as the trabeculae carneae, with spaces between them. 
(4)   When the musculature within a chamber wall contracts, the lumen (cavity) decreases in diameter. This is particularly true of the left ventricle. There is also a twisting or wringing action of the left ventricle that causes the apex of the heart to hit against the inner surface of the chest wall--the apex beat. 
(5)  The stroke volume is the amount of blood forced out of each ventricle in one contraction. The cardiac output is the volume of blood pumped out of the ventricles (RT into the lungs, LT into the systemic circulation) in one minute (expressed in liters per minute). These volumes will change according to the needs of the body. 
10-27. CARDIAC VALVES

Valves are structures that ensure that fluids will pass through them in only one direction. That is, a valve will open to allow fluids to pass in one direction but will close to prevent fluids from passing in the other direction. There are two sets of cardiac valves--the atrioventricular (AV) valves and the semilunar valves. Although the two sets of valves are quite different in design, they both function passively in response to the flow of the blood. 

AV Valves. The AV valves are found between the atria and the ventricles. The AV valves consist of flaps, known as cusps. The outer margin of each flap is attached to the inner surface of a fibrous ring. The inner edge of each flap is free. 
(1)  On the right side is the tricuspid valve. On the left side is the mitral valve. ("Might is never right.") 
(a)  Thus, the tricuspid valve is between the right atrium and the right ventricle. It is named for its three cusps. 
(b)  The mitral valve is located between the left atrium and the left ventricle. Since it has two cusps, it is sometimes called the "bicuspid" valve. 
(2) The contraction of the atrial walls forces the blood from the atria through the AV valves and into the ventricles (atrial systole). 
(3)  When the atria relax (atrial diastole) and the ventricles contract, the pressure would tend to drive the blood back into the atria. However, each opening is sealed when the cusps of each AV valve meet in the valve center. This prevents blood from flowing further back into the atria. 
(4)  A special anatomic arrangement helps prevent backward flow into the atria. Chordae tendineae are fibrous cords attached to the ventricular side of the cusps. Since these cords of dense FCT have a fixed length, they cannot be stretched or shortened. The other ends of these cords are attached to the papillary muscles. The papillary muscles are special extensions of the muscular walls of the ventricles. As the ventricles contract and become smaller, these muscles take up the slack in the cords. 
Semilunar (Aortic and Pulmonary) Valves. As mentioned before, the bases of the two great arteries (the pulmonary arch and the aortic arch) begin at their respective ventricles as short cylinders of the fibrous skeleton. Within each of these cylinders are three cuplike cusps, which make up each semilunar valve. When the ventricles contract (ventricular systole) and the AV valves have closed, the blood moves out into the great arteries through the semilunar valves. When the ventricles relax (ventricular diastole), the back pressure of the blood in the great arteries forces the cusps of the semilunar valves to the center and seals off each opening. 
10-28. NAVL OF THE HEART 

Controls of Heart Function. 
(1) Extrinsic controls. A number of cardiac nerves arise from both the sympathetic and parasympathetic portions of the nervous system (chapter 12). The sympathetic portion accelerates the action of the heart, while the parasympathetic portion slows it down. These portions are both controlled by cardiovascular centers in the medulla of the hind-brainstem. In addition, as everyone is well aware, various emotional states can affect the actions of the heart. 
(2) Intrinsic controls. Within the substance of the heart, certain fibers of the myocardium have been transformed from contracting muscle tissue to impulse-transmitting fibers. These are called Purkinje's fibers. Together, these fibers provide intrinsic control for the action of the heart. 
(a) The sinoatrial (SA) node is a collection of these fibers in the interatrial septum. The SA node is often called the pacemaker of the heart because it initiates each cycle of the contractions of the heart chambers. 
(b) The atrioventricular (AV) node is another group of these fibers just above the interventricular septum. 
(c)  Descending from the AV node is the bundle of His, which branches into the right and left septal bundles. These branches pass down on either side of the interventricular septum. 
(d) Impulse begin in the SA node, pass to the AV node, and then descend through the septal bundles to stimulate the myocardium of the ventricular walls to contract. 
(3) Humoral control. Apparently, some substances transported by the blood can accelerate or slow the action of the heart. This situation is called the humoral control of heart action. 
Coronary Arteries. Previously, we have described the flow of blood through the chambers of the heart. This blood, upon which the heart acts, is called functional blood. Now, we wish to discuss the supply of nutrient blood to the heart. This blood nourishes the tissues of the heart. The nutrient blood supplies oxygen and food materials to the tissues of the heart and removes waste materials. This nutrient blood is supplied to the walls of the heart by the right and left coronary arteries. 
(1)  The openings leading into the coronary arteries are located in the base of the ascending aorta, just above (behind the cusps of) the semilunar valve (aortic valve). When this valve is open, its cusps cover the openings of the coronary arteries. When the valve is closed, the backpressure of the blood in the aorta fills the coronary arteries with blood. The coronary arteries then distribute the blood to all of the tissues of the relaxed heart. 
(2)  Many of the branches of the coronary arteries are of the end artery type. This means that such a branch is the sole supply of nutrient blood to a specific area of the heart. If the branch should be closed for any reason, the tissue in that area will die for lack of oxygen and nourishment. 
Cardiac Veins and Coronary Sinus. The blood from the tissues of the heart is collected by the cardiac veins. These veins empty into the coronary sinus, a vessel, which in turn empties into the right atrium. 
Thebesian Veins. The thebesian veins are many minute sinuses found in the myocardium of the ventricles. They extend from the lumen into the myocardium of each ventricle. 
10-29. HEART SOUNDS

When the valves of the heart close, they produce audible sounds. First, the closing of the AV valves produces a noticeable "LUB." When the semilunar valves subsequently close, another sound "DUB" is produced to complete the cycle. These are referred to as the heart sounds--"LUB DUB, LUB DUB," etc.

10-30. ELECTROCARDIOGRAM (EKG)

Since the myocardial tissue is living material, its activity produces electrical impulses. With an electrocardiogram, the pattern of these electrical impulses can be recorded.

10-31. THE PERICARDIUM 

General. The heart is an active organ of the human body. Its pumping action, which begins in the very early embryo, continues without stopping until death. During each cycle of its activity, the heart changes in shape and size and tends also to rotate. (The number of cycles per minute is called heart rate.) To reduce the amount of friction resulting from this activity, the heart is includes within a serous sac, called the pericardium, or pericardial sac. 
Serous Space and Two Serous Pericardia. As in all serous cavities, there is a serous space between two serous membranes. 
(1)  The visceral pericardium intimately covers the surface of the heart. Earlier, we referred to this as the epicardium. 
(2)  The parietal pericardium is the outer serous membrane. 
(3)  Between the two serous pericardia is a very thin space containing a thin film of pericardial fluid. This lubricating fluid makes the action of the heart much less strenuous. 
Fibrous Pericardium. The parietal pericardium is covered with a very dense fibrous envelope. This envelope forms the outer portion of the pericardial sac. 
 Lesson 1
THE KIDNEY

8-1. INTRODUCTION TO THE URINARY SYSTEM 

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0802.jpg]]


The urinary system is a collection of organs to rid the body of nitrogenous wastes. These nitrogenous wastes are created by the metabolism of proteins. 
The urinary system includes the organs known as the kidney, the ureters, the urinary bladder, and the urethra (Figure 8-1). Together, these organs remove the nitrogenous wastes from the circulating blood, concentrate them into a fluid known as urine, and eliminate the urine from the body. 
8-2. GENERAL ANATOMY OF THE KIDNEY

In the human, there are two kidneys, one right and one left. 

Location. Both kidneys are attached high up on the posterior abdominal wall. The left kidney is slightly higher than the right. 
Shape. In the adult, each kidney measures about 1x2x4 inches. The kidneys have a kidney-bean shape. That is, they are notched on the medial side, they have a convex lateral curvature, and their front and rear surfaces are somewhat flat. 
Capsule. Each kidney is surrounded by a dense FCT membrane called a capsule. 
Internal Structure. When a kidney is cut from side to side, the internal structure is similar to that in Figure 8-1. There is a fleshy portion surrounding a central opening. The fleshy portion is divided into an outer cortex layer and an inner medulla. 
(1) The medulla consists of a series of pyramids whose apices (peaks) point into the hollow center of the kidney. The apex (peak) of each renal pyramid is known as the papilla.



Figure 8-1. The human urinary system.

(2) The central cavity of the kidney is known as the renal sinus. Its opening on the medial aspect of the kidney is known as the hilus (or hilum). The sinus contains a number of structures:

(a)  The spaces among these structures are filled with loose areolar FCT (fibrous connective tissue) and fat. 
(b  The renal NAVL enter the kidney directly from the abdominal aorta, through the hilus, and into the renal sinus. They then continue in a regular pattern throughout the medulla and cortex of the kidneys. 
(c)   A funnel-shaped, cup-like tube, called a calix (or calyx), surrounds the papilla of each pyramid. All of the calices are continuous with and empty into a hollow structure called the renal pelvis. 
e. Adherence to the Posterior Abdominal Wall. Each kidney is attached to the posterior abdominal wall on its respective side. Enclosing the kidneys and holding them in place are special perirenal fascial membranes and perirenal fats. During a "crash diet," an individual may lose some of this perirenal fat. This allows the kidney to move with the motions of the body. If the kidney should slump too far down, a kink may form in the ureter. This would prevent the normal flow of urine from the kidney to the bladder.

8-3. THE NEPHRON

The actual unit of kidney function is the structure referred to as the nephron (Figure 8-2). It is estimated that each kidney has about a million nephrons. Each nephron consists of a renal corpuscle and a tubular system. 

Renal Corpuscle. A nephron begins with a renal corpuscle. The renal corpuscle is made up of a double-walled capsule and an arterial capillary network known as the glomerulus. An afferent arteriole supplies blood to the glomerulus, and an efferent arteriole drains blood from the glomerulus. 
AFFERENT = carry to EFFERENT = carry away from

The blood from the afferent arteriole fills the glomerulus. Because of a pressure gradient, a large percentage of fluid in this blood passes through the wall of the glomerular capillary. The fluid then passes through the inner wall of the capsule. This brings the fluid into the hollow space between the inner and outer walls of the capsule.

Tubular System. The fluid, or filtrate, then passes through the tubular system of the nephron. Here, the majority of the water, glucose, and other valuable substances are reabsorbed from the fluid and returned to the cardiovascular system. 
Thus, at the end of the tubular system, the result is a very concentrated fluid containing the nitrogenous wastes. This concentrated fluid is called urine.



Figure 8-2. A "typical" nephron. 

8-4. COLLECTION OF URINE

The urine from each nephron flows into a collecting tubule (straight renal tubule). The collecting tubules merge until they form one of the papillary ducts that open at the papilla of the renal pyramid. At the papilla, the urine empties into the calices. The urine then flows into the renal pelvis in the sinus of the kidney.
 
 Lesson 8
OTHER CIRCULATORY SYSTEMS

10-44. THE LYMPHATIC SYSTEM

In general, the lymphatic system is a drainage system that picks up tissue fluids and returns them to the cardiovascular system. The tissue fluids are picked up in the interstitial spaces. They are eventually returned to the veins. 

Lymphatic Capillaries and Vessels. 
(1)  Within the tissue spaces, the lymphatic system begins with lymph capillaries. A lymph capillary begins with a blind end (cul-de-sac). 
(2)  The capillaries eventually come together to form lymphatic vessels, which gradually join and become larger and larger. Physiologically, lymphatic vessels are very similar to veins. Like veins, they have low pressure and possess valves. 
(3)  The thoracic duct is a major collecting vessel of the lymphatic system that empties into the deep veins of the neck. It begins in the upper posterior abdomen with a collection of sacs called the cisterna chyli. The cisterna chyli is a receiving area for lymph from three other major lymphatic vessels. From the cisterna chyli, the thoracic duct passes upward through the thorax and into the root of the neck. There, it empties into the deep veins of the neck. 
Lymph Nodes. Along the lymphatic vessels at various intervals are small structures known as lymph nodes. The lymph nodes function as sieves for the lymph passing through them. In healthy individuals, the lymph nodes usually draw no attention. However, in chronic diseases, the lymph nodes become enlarged and hardened (indurated). In the axilla, the inguinal region, and the neck, certain lymph nodes are large enough to be palpated even in health. Tonsils are aggregates of lymphatic tissue. 
Lymphocytes. Associated with the lymphatic system are special cells known as lymphocytes. The lymphocytes become part of the formed elements of the blood. They are primarily involved in the immune reactions of the body. 
10-45. CIRCULATORY SYSTEMS OF LESSER VOLUME

In addition to the cardiovascular and lymphatic circulatory systems, there are other circulatory systems of lesser volume. 

The cerebrospinal fluid (CSF) system is involved with the central nervous system. CSF is formed with fluid from the arteries and eventually returned to venous vessels. 
The bulbus oculi (eyeball) and the inner ear are fluid-filled hollow organs. Such organs have their own internal circulatory systems. In the case of the bulbus oculi, the fluid is the aqueous humor. In the case of the inner ear, the fluid is the endolymph/perilymph. In such cases, the fluids are produced from fluids of arterial vessels and then are picked up by venous vessels. Should the drainage pattern be interrupted, fluids will accumulate and cause increased pressure within the hollow organ. The increased pressure will interfere with the organ functions; examples are glaucoma of the eye and deafness of the ear. 
 
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0901.jpg]]

[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig0901.jpg]]

9-11. PRIMARY SEX ORGAN--TESTIS

The testis is the primary sex organ (gonad) of the male 

Location. Each male has a pair of testes located within the scrotum. The scrotum is a sac suspended from the inferior end of the trunk, between the thighs. Each testis is within a separate serous cavity within the scrotum. 
(1)   Migration. Originally, testes develop within the posterior abdominal region of the body. However, during development, they "migrate" out of the body cavity, through the inguinal canal of the abdominal wall, and into the scrotum. 
(2)  Temperature control. For the production of mature sperm (spermatozoa), the testes must be at a temperature that is a few degrees lower than that of the body cavity. For this reason, the testes are located outside of the body cavity. 
(a) Under cold conditions, each testis is pulled up toward the body by the cremaster muscle. At the same time, the dartos muscle of the scrotal wall contracts and thus reduces the exposed surface area and thickens the wall. 
(b) Under warm conditions, these structures are "relaxed." This allows the scrotum with the testes to hang free. 
(c)  If a boy baby is born with undescended testes (either in the abdominal cavity or inguinal canal) and if nothing is done to bring the testes into the scrotum, he will be sterile. 
Production of Spermatozoa. Millions of spermatozoa (male gametes) are produced by the seminiferous tubules of the testis. 
SEMEN = seed
FER = to carry

The male sex hormones (and rogens) are also produced by cells of the testes. 

9-12. SECONDARY SEX ORGANS

In general, the secondary sex organs of the male are responsible for the transport and care of the spermatozoa. 

Epididymis. The spermatozoa pass from the seminiferous tubules into the tubular structure known as the epididymis. The epididymis is a very long tube, but it is coiled and attached to the surface of the testis in the scrotum. As the spermatozoa pass along the length of the epididymis, they are nurtured by the secretions of the epididymal wall. During this passage through the epididymis, the spermatozoa become mature functioning gametes. They remain in the epididymis until "called for." 
Ductus (Vas) Deferens. During sexual excitement, the spermatozoa leave the epididymis and are carried by another duct known as the ductus deferens. The ductus deferens passes through the inguinal canal, enters the body cavity, and turns into the pelvic cavity. 
Seminal Vesicle. At the posterior surface of the prostate gland, the ductus deferens is joined by another duct called the seminal vesicle. The seminal vesicle is also a long tubular structure, but it is coiled up into a small mass at the back of the prostate gland. The seminal vesicle produces a nutrient fluid that helps to maintain the spermatozoa. 
Ejaculatory Duct. On each side, as the ductus deferens and seminal vesicle join, they form a single tube on the same side, called the ejaculatory duct. Each ejaculatory duct, left and right, carries the seminal vesicle secretion and spermatozoa through the substance of the prostate gland. Each ejaculatory duct empties into the prostatic urethra. 
Prostate Gland. The prostate gland is located in the pelvic cavity immediately under the urinary bladder. The urethra of the urinary system passes through the substance of the prostate gland, where it is known as the prostatic urethra. The prostate gland also adds a secretion. Altogether, the combination of secretions and spermatozoa is known as the semen. 
Urethra. In the male, the urethra is common to both the urinary system and the reproductive system. At different times, it carries either the urine or the semen. 
(1)  As already mentioned, the initial part of the urethra passes through the prostate gland and is called the prostatic urethra. 
(2) Immediately below the prostate gland, the urethra passes through the perineal membrane. Here, it is surrounded by the external urethral sphincter. This short section of the urethra is called the membranous urethra. 
(3)  That portion of the urethra passing through the penis (discussed below) is known as the penile urethra. 
Penis. The penis is a structure attached to the pubic arch of the bony pelvis and to the underside of the perineal membrane. It is an external structure of the male genital system, which is capable of enlargement and stiffening (erection). 
(1) The most favorable position for the deposit of semen (spermatozoa) is the upper recess of the vagina. This is opposite the opening of the cervix of the uterus. For this purpose, the penis is inserted into the female vagina ("sheath"). 
(2) Covering the glans ("head") of the penis is a fold of skin called the prepuce. In many cultures, the prepuce is removed shortly after birth in the procedure called circumcision. At the base of the glans, there are glands that secrete a lipid-like material called smegma. Thus, there is a need for continual cleanliness. 
9-13. SECONDARY SEXUAL CHARACTERISTICS

The secondary sexual characteristics of the male are those features designed to make a male attractive to the female. They help ensure that the two sexes will get together to produce the new generation. Among the more obvious of these features are muscularity, deep voice, and hair distribution.
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1201.jpg]]

Lesson 1
INTRODUCTION

12-1. THE NEURON

The neuron (nerve cell) is the conducting unit of the nervous system. It is specialized to be irritable and transmit signals, or impulses. The neurons are held together and supported by another nervous tissue known as neuroglia, or simply glia.

12-2. MAJOR SUBDIVISIONS OF THE NERVOUS SYSTEM

The human nervous system can be considered in three major subdivisions: 

The central nervous system (CNS). 
The peripheral nervous system (PNS). 
The autonomic nervous system (ANS). 
12-3. DEFINITIONS 

Neuron. A neuron (Figure 12-1) is the nerve cell body plus all of its processes and coverings. 


Figure 12-1. A "typical" neuron. 

Nerve. A nerve is a collection of neuron processes together and outside of the CNS. 
Fiber Tract. A fiber tract is a collection of neuron processes together and within the CNS. 
Ganglion. A ganglion is a collection of nerve cell bodies together and outside of the CNS. 
Nucleus. A nucleus is a collection of nerve cell bodies together and within the CNS. 
General Versus Special. If a nervous element is found throughout the body, it is said to be general. A nervous element located in just one part of the body, such as the head, is said to be special. For example, there are general senses, such as pain and temperature, and there are special sense organs, such as the eyes and the ears. 
Somatic Versus Visceral. 
(1) The term somatic refers to the peripheral part of the body. Thus, when we speak of somatic innervation, we are talking about the nerve supply to the trunk wall, upper and lower members, head, and neck. 
SOMA = body, body wall

(2) The term visceral refers to the visceral organs. These include hollow organs with smooth muscle (such as the intestines and the blood vessels) as well as sweat glands. Thus, visceral innervation refers to the nerve supply for these organs. Note that the visceral organs are located within both the trunk and periphery of the body. Those in the periphery include the blood vessels and the sweat glands. 
12-4. OVERVIEW OF THE HUMAN NERVOUS SYSTEM

The human nervous system is an integrated, connected circuitry of nervous tissues. 

It is supplied with special junctions called synapses. The synapses ensure the flow of information along the circuitry in the proper direction. 
In general terms, the human nervous system can be compared to a computer. There is input--the sensory information. There is central collation of input along with previously stored information. 
COLLATE = collect, compare, and arrange in order

Once a decision has been reached by the central portion, there is an output of commands to the effector organs (muscles and/or glands).

There are various control systems to be found within the body. Of these, the nervous system is the most rapid and precise in responding to specific situations. 

 


 
 Lesson 5
THE PANCREATIC ISLETS (ISLANDS OF LANGERHANS)

11-11. LOCATION AND STRUCTURE

There are small groups of cells, known as islets, distributed through the substance of the pancreas. These cells function independently of the pancreas and produce their own hormones.

11-12. HORMONES

Insulin and glucagon are two important hormones of the islets. These hormones are concerned with the glucose levels in the body.
 
 Lesson 3
THE PERIPHERAL NERVOUS SYSTEM (PNS)

12-8. PERIPHERAL NERVES

Connecting the CNS to all parts of the body are individual organs known as nerves. A nerve is a collection of neuron processes together and outside of the CNS. Peripheral nerves are nerves which pass from the CNS to the periphery of the body. Together, they are referred to as the peripheral nervous system. 

These nerves are bilateral and segmental. 
(1) Bilateral. This means that the peripheral nerves occur in pairs. In each pair, there is one nerve to the right and one to the left. 
(2) Segmental. The pairs of peripheral nerves occur in intervals, corresponding to the segments of the human embryo. 
Peripheral nerves connected to the brainstem are called cranial nerves. They are numbered from I through XII and also have individual names. 
Peripheral nerves connected to the spinal cord are called spinal nerves. They are identified by a letter representing the region of the vertebral column and a number representing the sequence in the region: 
Cervical: C-1 through C-8. 
Thoracic: T-1 through T-12. 
Lumbar: L-1 through L-5. 
Sacral: S-1 through S-5. 
Coccygeal. 
Thus, there are 31 pairs of spinal nerves.

12-9. A "TYPICAL" SPINAL NERVE (FIGURE 12-7)

In the human body, every spinal nerve has essentially the same construction and components. By learning the anatomy of one spinal nerve, you can understand the anatomy of all spinal nerves. Like a tree, a typical spinal nerve has roots, a trunk, and branches (rami).



Figure 12-7. A typical spinal nerve, with a cross section of the spinal cord.

Coming off of the posterior and anterior sides of the spinal cord are the posterior (dorsal) and anterior (ventral) roots of the spinal nerve. An enlargement on the posterior root is the posterior root ganglion. A ganglion is a collection of neuron cell bodies, together, outside the CNS. 
Laterally, the posterior and anterior roots of the spinal nerve join to form the spinal nerve trunk. The spinal nerve trunk of each spinal nerve is located in the appropriate intervertebral foramen of the vertebral column. (An intervertebral foramen is a passage formed on either side of the junction between two vertebrae.) 
Where the spinal nerve trunk emerges laterally from the intervertebral foramen, the trunk divides into two major branches. These branches are called the anterior (ventral) and posterior (dorsal) primary rami (ramus, singular). The posterior primary rami go to the back. The anterior primary rami go to the sides and front of the body, and to the upper and lower members. 
 
[img[http://www.free-ed.net/sweethaven/MedTech/Physiology/007fig1207.jpg]]
 Lesson 3
THE PINEAL GLAND

11-7. LOCATION

The pineal gland is located just above the brainstem. It is between the cerebral hemispheres.

11-8. FUNCTIONS

The details of the secretions and functions of the pineal gland are still not fully understood. Apparently, they are associated with sexual drive and reproduction. At least in lower animals, the pineal gland is influenced by the cumulative number of hours of light passing into the eyes each day.
 
Lesson 2
THE PITUITARY BODY

11-4. GENERAL 

The pituitary body is located immediately under the brain. It is in a special hollow of the floor of the cranial cavity. The pituitary body is actually two glands: the posterior pituitary gland and the anterior pituitary gland. 
As a whole, the pituitary body produces a large number of hormones. These affect many tissues of the body. Many of these hormones are referred to as tropins (or trophins) because they cause development or activity of the tissues. 
11-5. POSTERIOR PITUITARY GLAND

In the embryo, the posterior pituitary gland develops as an outcropping (hypophysis) of the inferior part of the brain. Later in life, the posterior pituitary gland remains connected to the forebrain-stem. There is a series of nuclei in the forebrainstem which are together referred to as the hypothalamus. The hormones of the posterior pituitary gland are actually produced in the hypothalamus. The hormones pass from the hypothalamus to the posterior pituitary gland by way of neurosecretory fibers. From the posterior pituitary gland, the hormones are secreted into the blood. The main hormones of the posterior pituitary gland are: 

Antidiuretic hormone (ADH). ADH is involved with the resorption or salvaging of water within the kidneys. Antidiuretic hormone is produced under thirst conditions. 
Oxytocin. Oxytocin has several specific effects, particularly upon smooth muscle. It is involved with contractions of smooth muscle in the uterus and with milk secretion. 
11-6. ANTERIOR PITUITARY GLAND

In the embryo, the anterior pituitary gland develops from the roof of the pharynx. Eventually, it lies in front of and attached to the posterior pituitary gland. Certain cells of the hypothalamus produce specific secretions called releasing factors. A special venous portal system carries these releasing factors to the anterior pituitary gland. There, they stimulate the cells of the anterior pituitary gland to secrete their specific hormones. 

Somatotropin (Somatotrophic Hormone; Growth Hormone). Somatotropin stimulates the growth of the body in general. When this hormone is deficient, dwarfism results. When it is present in excess amounts, giantism results. 
Thyrotropin. Thyrotropin stimulates the thyroid gland to produce its hormones. 
Adrenocorticotropic Hormone (ACTH). Adrenocorticotropic hormone stimulates the adrenal (suprarenal) cortex to produce its hormones. 
Luteinizing Hormone (LH). Luteinizing hormone stimulates ovulation and luteinization of ovarian follicles in females and promotes testosterone production in males. 
Follicle-Stimulating Hormone (FSH). Follicle-stimulating hormone stimulates ovarian follicle growth in females and stimulates spermatogenesis in males. 
Prolactin. Prolactin stimulates milk production and maternal behavior in females. 
 Lesson 10
THE PULMONARY NAVL

7-38. NERVOUS CONTROL OF BREATHING

As we have seen, breathing is a combination of many factors. These factors are integrated and controlled by the nervous system. 

Respiratory reflexes are controlled by the respiratory center found in the medullary portion of the hindbrainstem. ( See lesson 12). The level of carbon dioxide (CO2) in the circulating blood is one of the major influences upon the respiratory reflex. 
The individual intercostal nerves innervate the intercostal muscles. 
The muscles attached to and moving the rib cage are innervated by their appropriate nerves. (Ultimately, almost every muscle in the body may be mobilized to assist in breathing.) 
The diaphragm is innervated by its own individual pair of phrenic nerves. 
7-39. FUNCTIONAL BLOOD SUPPLY

There are essentially two blood supplies for the lungs-nutrient blood and functional blood. Nutrient blood is carried by the bronchial arteries from the thoracic aorta. Nutrient blood provides nourishment and oxygen to the tissues of the lung. Functional blood is actually involved in the respiratory exchange of gases between the alveoli and the capillaries. Functional blood is brought to and from the lungs by the pulmonary cycle of the cardiovascular system. 

The pulmonary cycle originates in the right ventricle of the heart. Contraction of the right ventricle forces the blood into the pulmonary arch, which divides into the right and left pulmonary arteries to their respective lungs. Paralleling the branching of the respiratory tree, the arteries divide and subdivide within the lungs. These arteries lead to capillaries in the vicinity of the alveoli. The walls of these capillaries are thin enough to accommodate the passage of gases to and from the alveolus. 
The blood, now saturated with oxygen, is collected by the pulmonary venous system. The blood is deposited ultimately into the left atrium of the heart. 
 
Lesson 3
THE SPECIAL SENSE OF HEARING (AUDITORY SENSE)

13-10. INTRODUCTION

If a medium is set into vibration within certain frequency limits (average between 25 cycles per second and 18,000 cycles per second), we have what is called a sound stimulus (Figure 13-5). The sensation of sound, of course, occurs only when these vibrations are interpreted by the cerebral cortex of the brain at the conscious level. 

The human ear is the special sensory receptor for the sound stimulus. As the stimulus passes from the external medium (air, water, or a solid conductor of sound) to the actual receptor cells in the head, the vibrations are in the form of (1) airborne waves, (2) mechanical oscillations, and (3) fluid-borne pulses. 


Figure 13-5. Characteristics of sound. 

The ear (Figure 13-6) is organized in three major parts: external ear, middle ear, and internal (inner) ear. Each part aids in the transmission of the stimulus to the receptor cells. 


Figure 13-6. A frontal section of the human ear. 

13-11. THE EXTERNAL EAR

The external ear begins with a funnel-like auricle. This auricle serves as a collector of the airborne waves and directs them into the external auditory meatus. At the inner end of this passage, the waves act upon the tympanic membrane (eardrum). The external auditory meatus is protected by a special substance called earwax (cerumen).

13-12. THE MIDDLE EAR 

Tympanic Membrane. The tympanic membrane separates the middle and external ears. It is set into mechanical oscillation by the airborne waves from the outside. 
Middle Ear Cavity. Within the petrous bone of the skull is the air-filled middle ear cavity. 
(1) Function of the auditory tube. Due to the auditory tube, the air of the middle ear cavity is continuous with the air of the surrounding environment. The auditory tube opens into the lateral wall of the nasopharynx. Thus, the auditory tube serves to equalize the air pressures on the two sides of the tympanic membrane. If these two pressures become moderately unequal, there is greater tension upon the tympanic membrane; this reduces (dampens) mechanical oscillations of the membrane. Extreme pressure differences cause severe pain. The passage of the auditory tube into the nasopharynx opens when one swallows; therefore, the pressure differences are controlled somewhat by the swallowing reflex. 
(2) Associated spaces. The middle ear cavity extends into the mastoid bone as the mastoid air cells. The relatively thin roof of the middle ear cavity separates the middle ear cavity from the middle cranial fossa. 
Auditory Ossicles. There is a series of three small bones, the auditory ossicles, which traverse the space of the middle ear cavity from the external ear to the internal ear. The auditory ossicles function as a unit. 
(1) The first ossicle, the malleus, has a long arm embedded in the tympanic membrane. Therefore, when the tympanic membrane is set into mechanical oscillation, the malleus is also set into mechanical oscillation. 
(2) The second ossicle is the incus. Its relationship to the malleus produces a leverage system which amplifies the mechanical oscillations received through the malleus. 
(3) The third ossicle, the stapes, articulates with the end of the arm of the incus. The foot plate of the stapes fills the oval (vestibular) window. 
Auditory Muscles. The auditory muscles are a pair of muscles associated with the auditory ossicles. They are named the tensor tympani muscle and the stapedius muscle. The auditory muscles help to control the intensity of the mechanical oscillations within the ossicles. 
13-13. THE INTERNAL EAR 

Transmission of the Sound Stimulus. The foot plate of the stapes fills the oval (vestibular) window, which opens to the vestibule of the internal ear (Figure 13-7A). As the ossicles oscillate mechanically, the stapes acts like a plunger against the oval window. The vestibule is filled with a fluid, the perilymph. These mechanical, plunger-like actions of the stapes impart pressure pulses to the perilymph. 


Figure 13-7. Diagram of the scalae. 

Organization of the Internal Ear. The internal ear is essentially a membranous labyrinth suspended within the cavity of the bony (osseous) labyrinth of the petrous bone (Figure 13-8). The membranous labyrinth is filled with a fluid, the endolymph. Between the membranous labyrinth and the bony labyrinth is the perilymph. 


Figure 13-8. The labyrinths of the internal ear. 

The Cochlea. The cochlea is a spiral structure associated with hearing. Its outer boundaries are formed by the snail-shaped portion of the bony labyrinth. The extensions of the bony labyrinth into the cochlea are called the scala vestibuli and the scala tympani (Figure 13-7B). These extensions are filled with perilymph. 
(1) Basilar membrane (Figure 1 3-7B). The basilar membrane forms the floor of the cochlear duct, the spiral portion of the membranous labyrinth. The basilar membrane is made up of transverse fibers. Each fiber is of a different length, and the lengths increase from one end to the other. Thus, the basilar membrane is constructed similarly to a harp or piano. Acting like the strings of the instrument, the individual fibers mechanically vibrate in response to specific frequencies of pulses in the perilymph. Thus, each vibration frequency of the sound stimulus affects a specific location of the basilar membrane. 
(2) Organ of Corti. Located upon the basilar membrane is the organ of Corti. The organ of Corti is made up of hair cells. When the basilar membrane vibrates, the hair cells are mechanically deformed so that the associated neuron is stimulated. 
13-14. NERVOUS PATHWAYS FOR HEARING

The neuron (associated with the hair cells of the organ of Corti) then carries the sound stimulus to the hindbrainstem. Via a special series of connections, the signal ultimately reaches Brodmann's area number 41, on the upper surface of the temporal lobe (see para 12-36). Here, the stimulus is perceived as the special sense of sound. It is interesting to note that speech in humans is primarily localized in the left cerebral hemisphere, while musical (rhythmic) sounds tend to be located in the right cerebral hemisphere.

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 Lesson 5
THE SPECIAL SENSE OF SMELL (OLFACTION)

13-21. SENSORY RECEPTORS

Molecules of various materials are dispersed (spread) throughout the air we breathe. A special olfactory epithelium is located in the upper recesses of the nasal chambers in the head. Special hair cells in the olfactory epithelium are called chemoreceptors, because they receive these molecules in the air.

13-22. OLFACTORY SENSORY PATHWAY

The information received by the olfactory hair cells is transmitted by way of the olfactory nerves (cranial nerves I). It passes through these nerves to the olfactory bulbs and then into the opposite cerebral hemisphere. Here, the information becomes the sensation of smell.
 
 Lesson 6
THE SPECIAL SENSE OF TASTE (GUSTATION)

13-23. SENSORY RECEPTORS

Molecules of various materials are also dispersed or dissolved in the fluids (saliva) of the mouth. These molecules are from the food ingested (taken in). Organs known as taste buds are scattered over the tongue and the rear of the mouth. Special hair cells in the taste buds are chemoreceptors to react to these molecules.

13-24. SENSORY PATHWAY

The information received by the hair cells of the taste buds is transmitted to the opposite side of the brain by way of three cranial nerves (VII, IX, and X). This information is interpreted by the cerebral hemispheres as the sensation of taste.
 
 Lesson 2
THE SPECIAL SENSE OF VISION

13-3. THE RETINA

Within the bulbus oculi (eyeball) is an inner layer called the retina. See Figure 13-1 for the location of the retina within the bulbus oculi. See Figure 13-2 for the types of cells found within the retina.



Figure 13-1. A focal-axis section of the bulbus oculi.

 



Figure 13-2. Cellular detail of the retina. 

Visual Fields (Figure 13-3). When a human looks at an object, light from the right half of the visual field goes to the left half of each eye. Likewise, light from the left half of the visual field goes to the right half of each eye. Later, in paragraph 13-4, we will see how the information from both eyes about a given half of the visual field is brought together by the nervous system. 
Photoreception and Signal Transmission. The cells of the retina include special photoreceptor cells in the form of cones and rods. The light ray stimulus chemically changes the visual chemical of the cones and rods. This produces a receptor potential which passes through the bodies of the rods and cones and which acts at the synapses to induce a signal in the bipolar cells. This signal is then transmitted to the ganglion cells. 


Figure 13-3. Scheme of visual input. 

(1) Cones. The cones of the retina are for acute vision and also receive color information. The cones tend to be concentrated at the rear of the eyeball. The greatest concentration is within the macula lutea at the inner end of the focal axis (Figure 13-1). 
(2) Rods. Light received by the rods is perceived in terms of black and white. The rods are sensitive to less intensive light than the cones. The rods are concentrated to the sides of the eyeball. 
(3) Signal transmission. The stimulus from the photoreceptors (cones and rods) is transferred to the bipolar cells. In turn, the stimulus is transferred to the ganglion cells, the cells of the innermost layer of the retina. The axons of the ganglion cells converge to the back side of the eyeball. The axons leave the eyeball to become the optic nerve, surrounded by a dense FCT sheath. There are no photoreceptors in the circular area where the axons of the ganglion cells exit the eyeball; thus, this area is called the blind spot. 
13-4. NERVOUS PATHWAYS FROM THE RETINAS 

The two optic nerves enter the cranial cavity and join in a structure known as the optic chiasma. Leading from the optic chiasma on either side of the brainstem is the optic tract. In the optic chiasma, the axons from the nasal (medial) halves of the retinas cross to the opposite sides. Thus, the left optic tract contains all of the information from the left halves of the retinas (right visual field), and the right optic tract contains all of the information from the right halves of the retinas (left visual field). 
The optic tracts carry this information to the LGB (lateral geniculate body) of the thalamus. From here, information is carried to the posterior medial portions (occipital lobes) of the cerebral cortex, where the information is perceived as conscious vision. Note that the right visual field is perceived within the left hemisphere, and the left visual field is perceived within the right hemisphere. 
The LGB also sends information into the midbrainstem. This information is used to activate various visual reflexes. 
13-5. FOCUSING OF THE LIGHT RAYS 

The light rays, which enter the eyeball from the visual field, are focused to ensure acute vision. The majority of this focusing is accomplished by the permanently rounded cornea. 
Fine adjustments of focusing, for acuteness of vision, are provided by the crystalline lens (biconvex lens). See Figure 13-4. This is particularly important when changing one's gaze between far and near objects. 


Figure 13-4. Bending of the light rays by a biconvex lens. 

13-6. ACCOMMODATION

The additional focusing provided by the crystalline lens, mentioned above, is one of the processes involved in accommodation. Accommodation refers to the various adjustments made by the eye to see better at different distances. 

The crystalline lens is kept in a flattened condition by the tension of the zonular fibers (zonule ligaments; fibers of the ciliary zonule) around its equator, or margin. Contraction of the ciliary muscle of the eyeball releases this tension and allows the elastic lens to become more rounded. Since the elasticity of the crystalline lens decreases with age, old people may find it very difficult to look at close objects. 
A second process in accommodation is the constriction of the pupils. The diameter of the pupil (the hole in the middle of the iris) controls the amount of light that enters the eyeball. As a light source comes closer and closer, the intensity of the light increases greatly. Therefore, the pupils must be constricted to control the amount of light entering the eyeball as an object under view comes close to the individual. 
A third process in accommodation is the convergence of the axes of the two eyeballs toward the midline. Since both eyes tend to focus on the same object (binocular vision), there is an angle between the two axes. As an object draws closer, the angle increases to enable the axes to still intersect the object. 
13-7. EYE MOVEMENTS 

Convergent and Conjugate Eye Movements. In a conjugate eye movement, both eyeballs move through an equal angle in one direction, such as right or left. In a convergent eye movement, both eyeballs turn toward the midline to focus upon a nearby object. In both cases, the movement of the left and right eyeballs is highly coordinated so that an object may be viewed by both eyes. Therefore, the object can be perceived within both cerebral hemispheres in a binocular fashion. 
"Searching" and "Following" Eye Movements. "Searching" and "following" movements of the eyeball are also called, respectively, voluntary fixation movements and involuntary fixation movements. For the first type of movement, the eyeballs move in a searching pattern, without focusing on a particular object until it is located. Once an object is located, the eyeballs will continually fix on that object in a following-type motion. 
Eye Movements During Reading. During reading of printed or written material, the eyeball demonstrates several physical characteristics. The amount of material that can be recognized at a given glance occupies a given width of a written line. Each glance is referred to as a fixation. During a fixation, the eyeball is essentially not moving, and each eyeball is oriented so that the image falls upon the macula lutea (the maximum receptive area). Reading is a series of motions in which the eyeballs fixate on a portion of the written line and then move very rapidly to the next portion. 
Compensation for Head Movements (Vestibular Control of Eye Movements). Since the human body cannot be held absolutely still, the eyeballs must move in order to remain fixed upon an object. For this purpose, the eyeballs must be moved in the opposite direction and at the opposite speed of the movement of the head. This is accomplished by a delicate and complicated mechanism. This mechanism includes the motor neurons of the muscles of the eyeball and the vestibular nuclei of the hindbrain (responsible for balance and spatial orientation). 
13-8. VISUAL REFLEXES

In the sense of vision, one consciously perceives the various objects being looked upon. In addition to this, there are a number of protective reactions to visual input--the visual reflexes. 

When an unexpected visual stimulus occurs within the visual field, the individual's response will often include movement and other types of reaction. This is a part of the startle reflex. 
When there is a change in the amount of light entering the eyeball, the size of the pupil will change. This is the pupillary reflex. The muscles of the iris automatically constrict or dilate to control the amount of light entering the eyeball. 
In the blink reflex, the eyelids automatically move over the exterior surface of the eyeball. This reflex results in the automatic washing of the exterior surface of the eyeball with the lacrimal fluids. It also helps to keep the surface moist. 
13-9. LACRIMAL APPARATUS

The eyeball is suspended in the orbit and faces outward. Helping to fill the orbit are a number of structures associated with the eyeball; these are the adnexa. Among these other structures is the lacrimal apparatus. 

The lacrimal gland is located in the upper outer corner in front. Via small ducts, it secretes the lacrimal fluid into the space between the external surface of the eyeball and the upper eyelid. 
The inner surface of the eyelids and the outer surface of the eyeball are covered by a continuous membrane known as the conjunctiva. The lacrimal fluid keeps the conjunctiva transparent. Also, with the blink reflex, the lacrimal fluid washes away any foreign particles that may be on the surface of the conjunctiva. 
The free margins of the upper and lower eyelids have special oil glands. The oily secretion of these glands helps prevent the lacrimal fluid from escaping. 
With the movement of the eyeball and the eyelids, the lacrimal fluid is gradually moved across the exterior surface of the eyeball to the medial inferior corner. Here, the lacrimal fluid is collected into a lacrimal sac, which drains into the nasal chamber by way of the nasolacrimal duct. Thus, the continuous production of lacrimal fluid is conserved by being recycled within the body. 

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 Lesson 6
THE SUPRALARYNGEAL STRUCTURES

7-20. GENERAL FUNCTIONS

The general functions of the supra laryngeal structures (Figure 7-3) are to condition the in flowing air and to test it. Conditioning includes cleansing, warming, and moistening.

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Figure 7-3. Supra laryngeal structures. 

7-21. NOSE

The (external) nose is the beginning of the respiratory system in humans. It is located in the center of the front of the face. It is pyramid shaped, with the base facing inferiorly. The base consists of two openings called the nares or nostrils. These open into a pair of vestibules, one on each side. The nares are guarded by stiff nasal hairs. These nasal hairs serve to remove the larger particles (such as lint and cinders) from the inflowing air.

7-22. NASAL CHAMBERS

The vestibules of the nose are continuous posteriorly with the right and left nasal chambers. 

Nasal Septum. Like the vestibules, the nasal chambers are separated by a nasal septum, a vertical wall from front to back. Constructed of bone and cartilage, the nasal septum extends from the floor to the roof and from front to back. 
Mucoperiosteal Lining. Each nasal chamber is lined with a mucoperiosteal lining. This mucoperiosteal lining is a special combination of tissues, which are rich in blood vessels. This excellent supply of blood furnishes moisture and heat. On the surface of the mucoperiosteum are minute hair-like processes called cilia. The cilia continuously drive fluids on the surface to the rear. A part of the fluids secreted on the surface is a mucous material. As a part of the continuous process of cleansing the inflowing air, finer particles are trapped by the mucus. 
Conchae. Thus, the conditioning of the inflowing air depends upon direct contact with the mucoperiosteum. The greater the surface area, the more efficient will be the conditioning. The conchae are three shelf-like projections that extend from the lateral wall of each nasal chamber. Thus, a superior, a middle, and an inferior concha are found on each side. During ordinary breathing, the air enters the vestibules of the nose and passes through the lower portions of the nasal chambers in direct contact with the inferior and middle conchae. 
Olfactory Epithelium. As the air passes through the nasal chambers, some of the air reaches the superior recesses of the nasal chambers. In these superior recesses is found the olfactory epithelium. The olfactory epithelium contains special hair cells that can detect individual molecules found in the air. Thus, the sense of smell (olfaction), tests the quality of inflowing air. 
Paranasal Sinuses. Connected with each nasal chamber are cavities found in the middle layer of various skull bones. These cavities are the paranasal sinuses. Like the nasal chambers, they are lined with a continuation of the mucoperiosteum. Each paranasal sinus is named according to the bone in which it is located. The function of the paranasal sinuses is unknown. 
7-23. NASOPHARYNX

The two nasal chambers are continuous posteriorly with a single cavity known as the nasopharynx. 

Pharyngeal Tonsils ("Adenoids"). The pharyngeal tonsils are a pair of lymphoid aggregates in the upper posterior recess of the nasopharynx. 
Auditory (Pharyngeotympanic or Eustachian) Tubes. On each lateral wall of the nasopharynx is a small mound with a slit-like opening. This is the opening of the auditory tube, which passes laterally to the middle ear cavity. Because of this tube, the air pressures are kept equal on the inner and outer sides of the tympanic membrane (eardrum). 
Soft Palate. The floor of the nasopharynx is the soft palate. The soft palate is a musculomembranous structure. (Unlike the soft palate, the hard palate is bony. The hard palate forms the floor of the nasal chambers and the roof of the oral cavity.) 
7-24. PHARYNX AND FUNCTION OF SOFT PALATE

The nasopharynx (of the respiratory system) and the oropharynx (of the digestive system) are continuous posteriorly with the pharynx proper. During swallowing, the soft palate is raised like a trap door to close off the upper air passageways. This prevents movement of food into the upper air passageways.
 
 Lesson 4
THE THYROID AND PARATHYROID GLANDS

11-9. THE THYROID GLAND 

Location and Structure. The thyroid gland is located around the trachea, just below the larynx. It consists of two lobes, left and right. They are connected across the front of the trachea by an isthmus. 
Hormones. 
(1)  Thyroxin. The most important hormone produced by the thyroid gland is thyroxin. Thyroxin affects the basal metabolic rate (BMR), the level of activity of the body. Since iodine is an important element in the structure of thyroxin, the dietary intake of iodine is very important. When the gland is not functioning properly, it may become enlarged (goiter). Insufficient or excess thyroxin has serious effects on the body. 
(2)  Calcitonin. A second hormone of the thyroid gland is calcitonin. It is involved with calcium metabolism in the body. 
11-10. THE PARATHYROID GLANDS

On the posterior side of each thyroid lobe is a pair (2 + 2 = 4) of tiny bodies called the parathyroid glands. The hormone of the parathyroid glands is parathoromone. It is important in maintaining the calcium levels of the body. When excess thyroid tissue is removed in surgery, the surgeon takes care not to remove the parathyroid glands.
 
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 Lesson 2
THE BLOOD-THE VEHICLE OF THE CARDIOVASCULAR SYSTEM

10-9. DEFINITION

Blood is the vehicle of the cardiovascular system. Thus, the component actually transports substances.

10-10. PLASMA

Plasma makes up about 55 percent of the total blood volume. 

Water. The major constituent of plasma is water. The physical characteristics of water make it a very good vehicle. 
(1)  Since water is fluid, it can flow through the conduits. 
(2)  Since most substances can be dissolved in water, it is often known as the "universal solvent." 
(3)  At ordinary pressures, water is essentially non-compressible. 
(4)  In addition, water has important temperature characteristics. 
(a)  Water has an ample heat-carrying capacity. It can carry heat readily throughout the body. 
(b)  Some of this heat is transferred to the water of the sweat glands. Since water can dissipate great quantities of heat through evaporation, excess heat can be efficiently disposed of at the surface of the skin. 
Dissolved and Suspended Substances. To some extent, all transported substances are dissolved or suspended in the water of the plasma. These substances include various gases, end products of digestion, various control substances, and waste products. Also, there are three major plasma proteins--albumin, globulins, and fibrinogen. Together with dissolved salts (electrolytes), these plasma proteins help to maintain the tonicity of the plasma. In addition, fibrinogen is important to blood clotting. 
10-11. FORMED ELEMENTS

The remainder of the blood volume consists of the formed elements--the red blood cells, the white blood cells, and the platelets. In adults, these formed elements normally make up 40 percent to 45 percent of the total blood volume. (This measure is called the hematocrit.) 

Red Blood Cells (RBCs; Erythrocytes). The primary function of RBCs is to contain the protein called hemoglobin, which in turn carries oxygen. Thus, RBCs carry the majority of the oxygen to the individual cells of the body. 
(1)  Structure. The normal, mature red blood cell is a biconcave disc. The biconcave shape results from the loss of the nucleus just before the final maturation of the RBC. Since this shape increases the surface area of the disc, there is an increase in the capacity for the flow of substances into and out of the RBC. 
(2)  Hemoglobin. Within the cytoplasm of the RBC is a special protein called hemoglobin. Because of its iron atoms, hemoglobin has a great affinity for oxygen. It will readily pick up oxygen until it is saturated. At the same time, however, hemoglobin will readily give up oxygen in areas of low concentration. 
(3)  Life cycle of the RBC. Because of the loss of its nucleus, the RBC has a limited life period (about 120 days). At the end of this period, the spleen removes the "worn out" RBC, and the liver salvages the "pieces," particularly the iron. 
White Blood Cells (WBCs; Leukocytes). The white blood cells are also formed elements of the blood. There are several types. 
(1)  Neutrophils and other phagocytic WBCs. The phagocytic WBCs can move independently out of the capillaries and penetrate into the tissues of the body. There, they actively attack foreign substances and engulf them in a process called phagocytosis. When these WBCs are overcome by foreign substances and die, their bodies accumulate to form a substance called pus. 
(2)  Lymphocytes. The lymphocytes are involved with the immune system of the body, including the production of antibodies. 
Platelets. The platelets are the third type of formed element in the blood. Platelets are fragments of former cells. They are very important in the clotting process. 
10-12. SERUM

After blood has been treated to remove the formed elements and the protein fibrinogen, there is a clear light-straw-colored fluid remaining. This fluid is called serum.

10-13. TRANSPORT OF GASES

One very important transport function of the blood is to carry gases back and forth between the lungs and the individual cells of the body. The alveoli and the individual body cells are the sites of exchange of gases to and from the blood. At these sites, the gases move according to the directions of pressure of concentration gradients. That is, each gas moves from an area where it is in higher concentration to an area of lesser concentration. 

Oxygen. Oxygen is in the air filling the alveolus of the lung. The oxygen passes through the walls of the alveolus and capillary to become dissolved in the plasma of the blood. Most of the dissolved oxygen is rapidly picked up by the hemoglobin of the RBCs. Thus, the RBC is the main transporting element for oxygen in the blood. 
Carbon Dioxide. Carbon dioxide is produced during metabolic oxidation within the individual cell. It passes through the cell membrane and the wall of the capillary to become dissolved in the plasma of the blood. Through action of an enzyme in the RBCs, most of the carbon dioxide (CO2) is transformed into bicarbonate ions (HCO3). 
10-14. TRANSPORT OF OTHER SUBSTANCES

Other substances, such as the end products of digestion, are also carried by the blood. They are either dissolved or suspended in the plasma.

10-15. IMPORTANCE OF BLOOD IN ENERGY MOBILIZATION

The life processes cannot continue in the body cells without sources of energy. From glucose, energy is released to produce ATP, the driving force of the life processes of the body. 

When a specific portion of the cerebral cortex is active, more blood is delivered to that portion. This is an example of how more blood can be delivered to the body parts where it is most needed. 
When the hormone epinephrine (Adrenalin) is secreted by the adrenal gland, it is delivered to all parts of the body by the cardiovascular system. Among other effects, epinephrine increases the rate of metabolism of all cells of the body. This helps to mobilize energy during a "fight-or-flight" stress reaction. 
In periods when much energy is required, the body can use its stores of fat as a source of energy. As we have seen in the chapter on the digestive system, the lymphatic circulatory system picks up the end products of lipid (fat) digestion and carries them to the cardiovascular system. 
(1) This fat is generally deposited throughout the body, particularly the subcutaneous layer, as yellow fat. In a rapid turnover, the high energy content of the fat is released for use throughout the body. 
(2) In infants, there is often brown fat at the junctions of the major blood vessels. In periods of high-energy requirements, this brown fat releases energy into the blood stream immediately. 
10-16. RESPONSES TO HEMORRHAGE

A blood vessel may be damaged by transection (cutting across) or rupture. At such points, a volume of whole blood can flow out of the blood vessels. This escape of blood from the blood vessels is called hemorrhage.

HEMO = blood
RRHAGE = excessive flow ("bursting forth")

Vascular contraction. The first response to a cut or ruptured vessels is contraction (spasm) of the blood vessel itself. This may considerably reduce the volume of blood loss. 
Platelet Plug. If the hole is small, a plug formed by clumping of the platelets may be adequate to stop the bleeding. 
Blood Clotting. There is a complicated process for sealing off holes or ends of blood vessels after a cut or rupture. By this process, called coagulation or clotting, the blood forms a solid mass to seal the opening where the blood is escaping. The mass is called a blood clot. After many intermediate steps, the protein fibrinogen of the blood is converted into sticky strands of fibrin. These sticky strands adhere to the wall of the opening and form a meshwork in the opening, which traps RBCs and plasma. Thus, the opening is sealed. 
Hematoma. A hematoma is a collection of blood, usually clotted, in an organ, space, or tissue. When found immediately beneath the skin, it will produce a purplish spot or mark. With time, as the clot is broken down and resorbed, the hematoma changes color and becomes smaller. 
Mobilization of Blood Reservoirs. Certain areas of the body contain enough blood that they can be used as reservoirs to maintain the circulating blood volume. This is important when a volume of blood has been lost through hemorrhage. Among these are the spleen and the liver, whose sinuses together can release several hundred milliliters of blood. Also important are several groups of veins, including the large abdominal veins, which can also provide several hundred milliliters of blood. 
10-17. BLOOD TRANSFUSIONS AND BLOOD MATCHING 

Transfusions. In cases where an individual has lost whole blood by hemorrhaging, it is often necessary to give transfusions of whole blood. Whole blood transfusions continue the functions of the RBCs. On the other hand, if an individual has suffered burns causing a loss of fluid but not the loss of formed elements, plasma or a plasma substitute will often be used. 
Blood Matching. There are a number of substances (antigens) on the surfaces of RBCs that vary among individuals. The blood of other individuals may contain or develop antibodies to these antigens. Before blood transfusions, the blood of the recipient and the donor must be matched to avoid potentially fatal reactions. Important systems of such antigens include the ABO system and the Rh system. 
 
The brain and spinal cord are the organs of the central nervous system. Because they are so vitally important, the brain and spinal cord, located in the dorsal body cavity, are encased in bone for protection. The brain is in the cranial vault, and

the spinal cord is in the vertebral canal of the vertebral column. Although considered to be two separate organs, the brain and spinal cord are continuous at the foramen magnum. Click here to learn more about the CNS. 
The Concept of the GALT
Tonsils and Peyer's patches, along with all the diffuse lymphatic tissue in the gastrointestinal tract and respiratory system, collectively are labeled gut associated lymphatic tissue, or GALT. The respiratory system arises in embryonic life as a diverticulum of the gut, and its lining cells, like those of the digestive tract, are derived from endoderm. The GALT is considered to be a lymphoid organ in its own right, which processes immunological challenges encountered in those systems.
Digestive System
Anatomy of the Digestive System
Functions of the Digestive System
Nutrition and Metabolism
Developmental Aspects of the Digestive System and Metabolism 


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Anatomy of the Digestive System

The digestive system consists of the alimentary canal (a hollow tube extending from mouth to anus) and several accessory digestive organs (Figure 14.1). The wall of the alimentary canal has four main tissue layers mucosa, submucosa, muscularis externa, serosa (Figure 14.2). The serosa (visceral peritoneum) is continuous with the parietal peritoneum, which lines the abdominal cavity wall. 

Organs of the alimentary canal: 

The mouth or oral cavity contains teeth and tongue and is bounded by lips, cheeks, and palate. Tonsils guard its posterior margin. 

The pharynx is a muscular tube that provides a passageway for food and air. 

The esophagus is a muscular tube that completes the passageway from the pharynx to the stomach. 

The stomach is a C-shaped organ located on the left side of the abdomen beneath the diaphragm (Figure 14.3). Food enters it through the cardio-esophageal sphincter and leaves it to enter the small intestine through the pyloric sphincter. The stomach has a third oblique layer of muscle in its wall that allows it to perform mixing or churning movements. Gastric glands produce hydrochloric acid, pepsin, renin, mucus, gastrin, and intrinsic factor. Mucus protects the stomach itself from being digested. 

The tubelike small intestine is suspended from the posterior body wall by the mesentery. Its subdivisions are the duodenum, jejunum, and ileum (Figure 14.4). Food digestion and absorption are completed here. Pancreatic juice and bile enter the duodenum through a sphincter at the distal end of the bile duct. Microvilli, villi, and circular folds increase the surface area of the small intestine for enhanced absorption. 

The large intestine frames the small intestine. Subdivisions are the cecum; appendix; ascending, transverse, and descending colon; sigmoid colon; rectum; anal canal (Figure 14.5). The large intestine delivers undigested food residue (feces) to the body exterior. 

Return to top 

Many accessory organs duct substances into the alimentary tube (Figure 14.6). 

The pancreas is a soft gland lying in the mesentery between the stomach and small intestine. Pancreatic juice contains enzymes (pancreatic amylase: acts on starch; trypsin: acts on protein; lipase: acts on lipids) in an alkaline fluid. 

The liver is a four-lobed organ overlying the stomach. Its digestive function is to produce bile, which it ducts into the small intestine. 

The gallbladder is a muscular sac that stores and concentrates bile. When fat digestion is not occurring, the continuously made bile backs up the cystic duct and enters the gallbladder. 

Salivary glands (three pairs - parotid, submandibular, sublingual) secrete saliva into the oral cavity. Saliva contains mucus and serous fluids. The serous component contains salivary amylase. 

Two sets of teeth are formed. The first set consists of 20 deciduous teeth that begin to appear at 6 months and are lost by 12 years. Permanent teeth (32) begin to replace deciduous teeth around 7 years. A typical tooth consists of crown covered with enamel and root covered with cementum. Most of the tooth is bonelike dentin. The pulp cavity contains blood vessels and nerves. 
Return to top 


Functions of the Digestive System

Foods must be broken down to their building blocks to be absorbed. Building blocks of carbohydrates are simple sugars, or monosaccharides, Building blocks of proteins are amino acids. Building blocks of fats, or lipids, are fatty acids and glycerol. 

Both mechanical (chewing) and chemical food breakdown begin in the mouth. Saliva contains mucus, which helps bind food together into a bolus, and salivary amylase, which begins the chemical breakdown of starch. Saliva is secreted in response to food in the mouth, mechanical pressure, and psychic stimuli. Essentially no food absorption occurs in the mouth. 

Swallowing has two phases: The buccal phase is voluntary; the tongue pushes the bolus into the pharynx. The involuntary pharyngeal-esophageal phase involves the closing off of nasal and respiratory passages and the conduction of food to the stomach by peristalsis. 

When food enters the stomach, gastric secretion is stimulated by vagus nerves and by gastrin (a local hormone). Hydrochloric acid activates the protein-digesting enzyme pepsin, and chemical digestion of proteins begins. Food is also mechanically broken down by the churning activity of stomach muscles. Movement of chyme into the small intestine is controlled by the enterogastric reflex. 

Chemical digestion of fats, proteins, and carbohydrates is completed in the small intestine by intestinal enzymes and, more importantly, pancreatic enzymes. Alkaline pancreatic juice neutralizes acid chyme and provides the proper environment for the operation of enzymes. Both pancreatic Juice (the only source of lipases) and bile (formed by the liver) are necessary for normal fat breakdown and absorption. Bile acts as a fat emulsifier. Secretin and cholecystokinin, hormones produced by the small intestine, stimulate release of bile and pancreatic juice. Segmental movements mix foods; peristaltic movements move foodstuffs along the small intestine. Most nutrient absorption occurs by active transport into the capillary blood of the villi (Figure 14.7). Fats are absorbed by diffusion into both capillary blood and lacteals in the villi. 

The large intestine receives bacteria-laden indigestible food residue. Activities of the large intestine are absorption of water and salts and of vitamins made by resident bacteria. When feces are delivered to the rectum by peristalsis and mass peristalsis. the defecation reflex is initiated. 
Return to top 


Nutrition and Metabolism

Metabolism includes all chemical breakdown (catabolic) and building (anabolic) reactions needed to maintain life (Figure 14.8). 

Carbohydrates, most importantly glucose, are the body's major energy fuel. As glucose is oxidized, carbon dioxide, water, and ATP are formed. The sequential pathways of glucose catabolism are glycolysis, which occurs in the cytosol, and the Krebs cycle and electron transport chain (in the mitochondria). During hypergiycemia, glucose is stored as glycogen or converted to fat. In hypoglycemia, glycogenolysis, gluconeogenesis, and fat breakdown occur to restore normal blood glucose levels. 

Fats insulate the body, protect organs, build some cell structures (membranes and myelin sheaths), and provide reserve energy. When carbohydrates are not available, more fats are oxidized to produce ATP. Excessive fat breakdown causes blood to become acidic. Excess dietary fat is stored in subcutaneous tissue and other fat depots. 

Proteins form the bulk of cell structure and most functional molecules. They are carefully conserved by body cells. Amino acids are actively taken up from blood by tissue cells; those that cannot be made by body cells are called essential amino acids. Amino acids are oxidized to form ATP mainly when other fuel sources are not available. Ammonia, released as amino acids are catabolized, is detoxified by liver cells that combine it with carbon dioxide to form urea. 

The liver is the body's key metabolic organ. Its cells remove nutrients from hepatic portal blood. It performs glycogenesis (glucose converted to and stored as glycogen), glycogenolysis (glycogen broken down into glucose), and gluconeogenesis (formation of glucose from proteins and fats) to maintain homeostasis of blood glucose levels. Its cells make blood proteins and other substances and release them to blood. Fats are burned by liver cells to provide some of their energy (ATP); excesses are stored or released to blood in simpler forms that can be used by other tissue cells. Phagocytic cells remove bacteria from hepatic portal blood. Most cholesterol is made by the liver; cholesterol breakdown products are secreted in bile. Fats and cholesterol are transported in the blood by lipoproteins. LDL's transport cholesterol to body cells; HDL's carry cholesterol to the liver for degradation. Cholesterol is used to make functional molecules and for some structural purposes; it is not used for energy. 

A dynamic balance exists between energy intake and total energy output (heat + work + energy storage). Interference with this balance results in obesity or malnutrition leading to body wasting. 

When the three major types of foods are oxidized for energy, they yield different amounts of energy, Carbohydrates and proteins yield 4 kcal/gram; fats yield 9 kcal/gram. Basal metabolic rate (BMR) is the total amount of energy used by the body when one is in a basal state. Age, sex, body surface area, and amount of thyroxine produced influence BMR. 

Total metabolic rate (TMR) is number of calories used by the body to accomplish all ongoing daily activities. It increases dramatically as muscle activity increases. When TMR equals total caloric intake, weight remains constant. 

As foods are catabolized to form ATP, more than 60 percent of energy released escapes as heat, warming the body. The hypothalamus initiates heat-loss processes (radiation of heat from skin and evaporation of sweat) or heat-promoting processes (vasoconstriction of skin blood vessels and shivering) as necessary to maintain body temperature within normal limits. Fever (hyperthermia) represents body temperature regulated at higher-than-normal levels. 
Return to top 


Developmental Aspects of the Digestive System and Metabolism

The alimentary tract forms as a hollow tube. Accessory glands form as outpocketings from this tube. 

Common congenital defects include cleft palate, cleft lip, and tracheoesophageal fistula, all of which interfere with normal nutrition. Common inborn errors of metabolism are phenylketonuria (PKU) and cystic fibrosis. 

Various inflammatory conditions plague the digestive system throughout life. Appendicitis is common in adolescents, gastroenteritis and food poisoning can occur at any time (given the proper irritating factors), ulcers and gallbladder problems increase in middle age. Obesity and diabetes mellitus are bothersome during later middle age. 

Efficiency of all digestive system processes decreases in the elderly. Gastrointestinal cancers, such as stomach and colon cancer, appear with increasing frequency in an aging population. 

[img[Digestive System
Anatomy of the Digestive System
Functions of the Digestive System
Nutrition and Metabolism
Developmental Aspects of the Digestive System and Metabolism 


--------------------------------------------------------------------------------


Anatomy of the Digestive System

The digestive system consists of the alimentary canal (a hollow tube extending from mouth to anus) and several accessory digestive organs (Figure 14.1). The wall of the alimentary canal has four main tissue layers mucosa, submucosa, muscularis externa, serosa (Figure 14.2). The serosa (visceral peritoneum) is continuous with the parietal peritoneum, which lines the abdominal cavity wall. 

Organs of the alimentary canal: 

The mouth or oral cavity contains teeth and tongue and is bounded by lips, cheeks, and palate. Tonsils guard its posterior margin. 

The pharynx is a muscular tube that provides a passageway for food and air. 

The esophagus is a muscular tube that completes the passageway from the pharynx to the stomach. 

The stomach is a C-shaped organ located on the left side of the abdomen beneath the diaphragm (Figure 14.3). Food enters it through the cardio-esophageal sphincter and leaves it to enter the small intestine through the pyloric sphincter. The stomach has a third oblique layer of muscle in its wall that allows it to perform mixing or churning movements. Gastric glands produce hydrochloric acid, pepsin, renin, mucus, gastrin, and intrinsic factor. Mucus protects the stomach itself from being digested. 

The tubelike small intestine is suspended from the posterior body wall by the mesentery. Its subdivisions are the duodenum, jejunum, and ileum (Figure 14.4). Food digestion and absorption are completed here. Pancreatic juice and bile enter the duodenum through a sphincter at the distal end of the bile duct. Microvilli, villi, and circular folds increase the surface area of the small intestine for enhanced absorption. 

The large intestine frames the small intestine. Subdivisions are the cecum; appendix; ascending, transverse, and descending colon; sigmoid colon; rectum; anal canal (Figure 14.5). The large intestine delivers undigested food residue (feces) to the body exterior. 

Return to top 

Many accessory organs duct substances into the alimentary tube (Figure 14.6). 

The pancreas is a soft gland lying in the mesentery between the stomach and small intestine. Pancreatic juice contains enzymes (pancreatic amylase: acts on starch; trypsin: acts on protein; lipase: acts on lipids) in an alkaline fluid. 

The liver is a four-lobed organ overlying the stomach. Its digestive function is to produce bile, which it ducts into the small intestine. 

The gallbladder is a muscular sac that stores and concentrates bile. When fat digestion is not occurring, the continuously made bile backs up the cystic duct and enters the gallbladder. 

Salivary glands (three pairs - parotid, submandibular, sublingual) secrete saliva into the oral cavity. Saliva contains mucus and serous fluids. The serous component contains salivary amylase. 

Two sets of teeth are formed. The first set consists of 20 deciduous teeth that begin to appear at 6 months and are lost by 12 years. Permanent teeth (32) begin to replace deciduous teeth around 7 years. A typical tooth consists of crown covered with enamel and root covered with cementum. Most of the tooth is bonelike dentin. The pulp cavity contains blood vessels and nerves. 
Return to top 


Functions of the Digestive System

Foods must be broken down to their building blocks to be absorbed. Building blocks of carbohydrates are simple sugars, or monosaccharides, Building blocks of proteins are amino acids. Building blocks of fats, or lipids, are fatty acids and glycerol. 

Both mechanical (chewing) and chemical food breakdown begin in the mouth. Saliva contains mucus, which helps bind food together into a bolus, and salivary amylase, which begins the chemical breakdown of starch. Saliva is secreted in response to food in the mouth, mechanical pressure, and psychic stimuli. Essentially no food absorption occurs in the mouth. 

Swallowing has two phases: The buccal phase is voluntary; the tongue pushes the bolus into the pharynx. The involuntary pharyngeal-esophageal phase involves the closing off of nasal and respiratory passages and the conduction of food to the stomach by peristalsis. 

When food enters the stomach, gastric secretion is stimulated by vagus nerves and by gastrin (a local hormone). Hydrochloric acid activates the protein-digesting enzyme pepsin, and chemical digestion of proteins begins. Food is also mechanically broken down by the churning activity of stomach muscles. Movement of chyme into the small intestine is controlled by the enterogastric reflex. 

Chemical digestion of fats, proteins, and carbohydrates is completed in the small intestine by intestinal enzymes and, more importantly, pancreatic enzymes. Alkaline pancreatic juice neutralizes acid chyme and provides the proper environment for the operation of enzymes. Both pancreatic Juice (the only source of lipases) and bile (formed by the liver) are necessary for normal fat breakdown and absorption. Bile acts as a fat emulsifier. Secretin and cholecystokinin, hormones produced by the small intestine, stimulate release of bile and pancreatic juice. Segmental movements mix foods; peristaltic movements move foodstuffs along the small intestine. Most nutrient absorption occurs by active transport into the capillary blood of the villi (Figure 14.7). Fats are absorbed by diffusion into both capillary blood and lacteals in the villi. 

The large intestine receives bacteria-laden indigestible food residue. Activities of the large intestine are absorption of water and salts and of vitamins made by resident bacteria. When feces are delivered to the rectum by peristalsis and mass peristalsis. the defecation reflex is initiated. 
Return to top 


Nutrition and Metabolism

Metabolism includes all chemical breakdown (catabolic) and building (anabolic) reactions needed to maintain life (Figure 14.8). 

Carbohydrates, most importantly glucose, are the body's major energy fuel. As glucose is oxidized, carbon dioxide, water, and ATP are formed. The sequential pathways of glucose catabolism are glycolysis, which occurs in the cytosol, and the Krebs cycle and electron transport chain (in the mitochondria). During hypergiycemia, glucose is stored as glycogen or converted to fat. In hypoglycemia, glycogenolysis, gluconeogenesis, and fat breakdown occur to restore normal blood glucose levels. 

Fats insulate the body, protect organs, build some cell structures (membranes and myelin sheaths), and provide reserve energy. When carbohydrates are not available, more fats are oxidized to produce ATP. Excessive fat breakdown causes blood to become acidic. Excess dietary fat is stored in subcutaneous tissue and other fat depots. 

Proteins form the bulk of cell structure and most functional molecules. They are carefully conserved by body cells. Amino acids are actively taken up from blood by tissue cells; those that cannot be made by body cells are called essential amino acids. Amino acids are oxidized to form ATP mainly when other fuel sources are not available. Ammonia, released as amino acids are catabolized, is detoxified by liver cells that combine it with carbon dioxide to form urea. 

The liver is the body's key metabolic organ. Its cells remove nutrients from hepatic portal blood. It performs glycogenesis (glucose converted to and stored as glycogen), glycogenolysis (glycogen broken down into glucose), and gluconeogenesis (formation of glucose from proteins and fats) to maintain homeostasis of blood glucose levels. Its cells make blood proteins and other substances and release them to blood. Fats are burned by liver cells to provide some of their energy (ATP); excesses are stored or released to blood in simpler forms that can be used by other tissue cells. Phagocytic cells remove bacteria from hepatic portal blood. Most cholesterol is made by the liver; cholesterol breakdown products are secreted in bile. Fats and cholesterol are transported in the blood by lipoproteins. LDL's transport cholesterol to body cells; HDL's carry cholesterol to the liver for degradation. Cholesterol is used to make functional molecules and for some structural purposes; it is not used for energy. 

A dynamic balance exists between energy intake and total energy output (heat + work + energy storage). Interference with this balance results in obesity or malnutrition leading to body wasting. 

When the three major types of foods are oxidized for energy, they yield different amounts of energy, Carbohydrates and proteins yield 4 kcal/gram; fats yield 9 kcal/gram. Basal metabolic rate (BMR) is the total amount of energy used by the body when one is in a basal state. Age, sex, body surface area, and amount of thyroxine produced influence BMR. 

Total metabolic rate (TMR) is number of calories used by the body to accomplish all ongoing daily activities. It increases dramatically as muscle activity increases. When TMR equals total caloric intake, weight remains constant. 

As foods are catabolized to form ATP, more than 60 percent of energy released escapes as heat, warming the body. The hypothalamus initiates heat-loss processes (radiation of heat from skin and evaporation of sweat) or heat-promoting processes (vasoconstriction of skin blood vessels and shivering) as necessary to maintain body temperature within normal limits. Fever (hyperthermia) represents body temperature regulated at higher-than-normal levels. 
Return to top 


Developmental Aspects of the Digestive System and Metabolism

The alimentary tract forms as a hollow tube. Accessory glands form as outpocketings from this tube. 

Common congenital defects include cleft palate, cleft lip, and tracheoesophageal fistula, all of which interfere with normal nutrition. Common inborn errors of metabolism are phenylketonuria (PKU) and cystic fibrosis. 

Various inflammatory conditions plague the digestive system throughout life. Appendicitis is common in adolescents, gastroenteritis and food poisoning can occur at any time (given the proper irritating factors), ulcers and gallbladder problems increase in middle age. Obesity and diabetes mellitus are bothersome during later middle age. 

Efficiency of all digestive system processes decreases in the elderly. Gastrointestinal cancers, such as stomach and colon cancer, appear with increasing frequency in an aging population. 

[img[http://lrn.org/Graphics/Digestive/figure%2014.1.gif]]

[img[http://lrn.org/Graphics/Digestive/figure%2014.2.gif]]

[img[http://lrn.org/Graphics/Digestive/figure%2014.3.gif]]

[img[http://lrn.org/Graphics/Digestive/figure%2014.4.gif]]

[img[http://lrn.org/Graphics/Digestive/figure%2014.5.gif]]

[img[http://lrn.org/Graphics/Digestive/figure%2014.6.gif]]

[img[http://lrn.org/Graphics/Digestive/figure%2014.7.gif]]

[img[http://lrn.org/Graphics/Digestive/figure%2014.8.gif]]
Digestive System
Anatomy of the Digestive System
Functions of the Digestive System
Nutrition and Metabolism
Developmental Aspects of the Digestive System and Metabolism 


--------------------------------------------------------------------------------


Anatomy of the Digestive System

The digestive system consists of the alimentary canal (a hollow tube extending from mouth to anus) and several accessory digestive organs (Figure 14.1). The wall of the alimentary canal has four main tissue layers mucosa, submucosa, muscularis externa, serosa (Figure 14.2). The serosa (visceral peritoneum) is continuous with the parietal peritoneum, which lines the abdominal cavity wall. 

Organs of the alimentary canal: 

The mouth or oral cavity contains teeth and tongue and is bounded by lips, cheeks, and palate. Tonsils guard its posterior margin. 

The pharynx is a muscular tube that provides a passageway for food and air. 

The esophagus is a muscular tube that completes the passageway from the pharynx to the stomach. 

The stomach is a C-shaped organ located on the left side of the abdomen beneath the diaphragm (Figure 14.3). Food enters it through the cardio-esophageal sphincter and leaves it to enter the small intestine through the pyloric sphincter. The stomach has a third oblique layer of muscle in its wall that allows it to perform mixing or churning movements. Gastric glands produce hydrochloric acid, pepsin, renin, mucus, gastrin, and intrinsic factor. Mucus protects the stomach itself from being digested. 

The tubelike small intestine is suspended from the posterior body wall by the mesentery. Its subdivisions are the duodenum, jejunum, and ileum (Figure 14.4). Food digestion and absorption are completed here. Pancreatic juice and bile enter the duodenum through a sphincter at the distal end of the bile duct. Microvilli, villi, and circular folds increase the surface area of the small intestine for enhanced absorption. 

The large intestine frames the small intestine. Subdivisions are the cecum; appendix; ascending, transverse, and descending colon; sigmoid colon; rectum; anal canal (Figure 14.5). The large intestine delivers undigested food residue (feces) to the body exterior. 

Return to top 

Many accessory organs duct substances into the alimentary tube (Figure 14.6). 

The pancreas is a soft gland lying in the mesentery between the stomach and small intestine. Pancreatic juice contains enzymes (pancreatic amylase: acts on starch; trypsin: acts on protein; lipase: acts on lipids) in an alkaline fluid. 

The liver is a four-lobed organ overlying the stomach. Its digestive function is to produce bile, which it ducts into the small intestine. 

The gallbladder is a muscular sac that stores and concentrates bile. When fat digestion is not occurring, the continuously made bile backs up the cystic duct and enters the gallbladder. 

Salivary glands (three pairs - parotid, submandibular, sublingual) secrete saliva into the oral cavity. Saliva contains mucus and serous fluids. The serous component contains salivary amylase. 

Two sets of teeth are formed. The first set consists of 20 deciduous teeth that begin to appear at 6 months and are lost by 12 years. Permanent teeth (32) begin to replace deciduous teeth around 7 years. A typical tooth consists of crown covered with enamel and root covered with cementum. Most of the tooth is bonelike dentin. The pulp cavity contains blood vessels and nerves. 
Return to top 


Functions of the Digestive System

Foods must be broken down to their building blocks to be absorbed. Building blocks of carbohydrates are simple sugars, or monosaccharides, Building blocks of proteins are amino acids. Building blocks of fats, or lipids, are fatty acids and glycerol. 

Both mechanical (chewing) and chemical food breakdown begin in the mouth. Saliva contains mucus, which helps bind food together into a bolus, and salivary amylase, which begins the chemical breakdown of starch. Saliva is secreted in response to food in the mouth, mechanical pressure, and psychic stimuli. Essentially no food absorption occurs in the mouth. 

Swallowing has two phases: The buccal phase is voluntary; the tongue pushes the bolus into the pharynx. The involuntary pharyngeal-esophageal phase involves the closing off of nasal and respiratory passages and the conduction of food to the stomach by peristalsis. 

When food enters the stomach, gastric secretion is stimulated by vagus nerves and by gastrin (a local hormone). Hydrochloric acid activates the protein-digesting enzyme pepsin, and chemical digestion of proteins begins. Food is also mechanically broken down by the churning activity of stomach muscles. Movement of chyme into the small intestine is controlled by the enterogastric reflex. 

Chemical digestion of fats, proteins, and carbohydrates is completed in the small intestine by intestinal enzymes and, more importantly, pancreatic enzymes. Alkaline pancreatic juice neutralizes acid chyme and provides the proper environment for the operation of enzymes. Both pancreatic Juice (the only source of lipases) and bile (formed by the liver) are necessary for normal fat breakdown and absorption. Bile acts as a fat emulsifier. Secretin and cholecystokinin, hormones produced by the small intestine, stimulate release of bile and pancreatic juice. Segmental movements mix foods; peristaltic movements move foodstuffs along the small intestine. Most nutrient absorption occurs by active transport into the capillary blood of the villi (Figure 14.7). Fats are absorbed by diffusion into both capillary blood and lacteals in the villi. 

The large intestine receives bacteria-laden indigestible food residue. Activities of the large intestine are absorption of water and salts and of vitamins made by resident bacteria. When feces are delivered to the rectum by peristalsis and mass peristalsis. the defecation reflex is initiated. 
Return to top 


Nutrition and Metabolism

Metabolism includes all chemical breakdown (catabolic) and building (anabolic) reactions needed to maintain life (Figure 14.8). 

Carbohydrates, most importantly glucose, are the body's major energy fuel. As glucose is oxidized, carbon dioxide, water, and ATP are formed. The sequential pathways of glucose catabolism are glycolysis, which occurs in the cytosol, and the Krebs cycle and electron transport chain (in the mitochondria). During hypergiycemia, glucose is stored as glycogen or converted to fat. In hypoglycemia, glycogenolysis, gluconeogenesis, and fat breakdown occur to restore normal blood glucose levels. 

Fats insulate the body, protect organs, build some cell structures (membranes and myelin sheaths), and provide reserve energy. When carbohydrates are not available, more fats are oxidized to produce ATP. Excessive fat breakdown causes blood to become acidic. Excess dietary fat is stored in subcutaneous tissue and other fat depots. 

Proteins form the bulk of cell structure and most functional molecules. They are carefully conserved by body cells. Amino acids are actively taken up from blood by tissue cells; those that cannot be made by body cells are called essential amino acids. Amino acids are oxidized to form ATP mainly when other fuel sources are not available. Ammonia, released as amino acids are catabolized, is detoxified by liver cells that combine it with carbon dioxide to form urea. 

The liver is the body's key metabolic organ. Its cells remove nutrients from hepatic portal blood. It performs glycogenesis (glucose converted to and stored as glycogen), glycogenolysis (glycogen broken down into glucose), and gluconeogenesis (formation of glucose from proteins and fats) to maintain homeostasis of blood glucose levels. Its cells make blood proteins and other substances and release them to blood. Fats are burned by liver cells to provide some of their energy (ATP); excesses are stored or released to blood in simpler forms that can be used by other tissue cells. Phagocytic cells remove bacteria from hepatic portal blood. Most cholesterol is made by the liver; cholesterol breakdown products are secreted in bile. Fats and cholesterol are transported in the blood by lipoproteins. LDL's transport cholesterol to body cells; HDL's carry cholesterol to the liver for degradation. Cholesterol is used to make functional molecules and for some structural purposes; it is not used for energy. 

A dynamic balance exists between energy intake and total energy output (heat + work + energy storage). Interference with this balance results in obesity or malnutrition leading to body wasting. 

When the three major types of foods are oxidized for energy, they yield different amounts of energy, Carbohydrates and proteins yield 4 kcal/gram; fats yield 9 kcal/gram. Basal metabolic rate (BMR) is the total amount of energy used by the body when one is in a basal state. Age, sex, body surface area, and amount of thyroxine produced influence BMR. 

Total metabolic rate (TMR) is number of calories used by the body to accomplish all ongoing daily activities. It increases dramatically as muscle activity increases. When TMR equals total caloric intake, weight remains constant. 

As foods are catabolized to form ATP, more than 60 percent of energy released escapes as heat, warming the body. The hypothalamus initiates heat-loss processes (radiation of heat from skin and evaporation of sweat) or heat-promoting processes (vasoconstriction of skin blood vessels and shivering) as necessary to maintain body temperature within normal limits. Fever (hyperthermia) represents body temperature regulated at higher-than-normal levels. 
Return to top 


Developmental Aspects of the Digestive System and Metabolism

The alimentary tract forms as a hollow tube. Accessory glands form as outpocketings from this tube. 

Common congenital defects include cleft palate, cleft lip, and tracheoesophageal fistula, all of which interfere with normal nutrition. Common inborn errors of metabolism are phenylketonuria (PKU) and cystic fibrosis. 

Various inflammatory conditions plague the digestive system throughout life. Appendicitis is common in adolescents, gastroenteritis and food poisoning can occur at any time (given the proper irritating factors), ulcers and gallbladder problems increase in middle age. Obesity and diabetes mellitus are bothersome during later middle age. 

Efficiency of all digestive system processes decreases in the elderly. Gastrointestinal cancers, such as stomach and colon cancer, appear with increasing frequency in an aging population. 

[img[Digestive System
Anatomy of the Digestive System
Functions of the Digestive System
Nutrition and Metabolism
Developmental Aspects of the Digestive System and Metabolism 


--------------------------------------------------------------------------------


Anatomy of the Digestive System

The digestive system consists of the alimentary canal (a hollow tube extending from mouth to anus) and several accessory digestive organs (Figure 14.1). The wall of the alimentary canal has four main tissue layers mucosa, submucosa, muscularis externa, serosa (Figure 14.2). The serosa (visceral peritoneum) is continuous with the parietal peritoneum, which lines the abdominal cavity wall. 

Organs of the alimentary canal: 

The mouth or oral cavity contains teeth and tongue and is bounded by lips, cheeks, and palate. Tonsils guard its posterior margin. 

The pharynx is a muscular tube that provides a passageway for food and air. 

The esophagus is a muscular tube that completes the passageway from the pharynx to the stomach. 

The stomach is a C-shaped organ located on the left side of the abdomen beneath the diaphragm (Figure 14.3). Food enters it through the cardio-esophageal sphincter and leaves it to enter the small intestine through the pyloric sphincter. The stomach has a third oblique layer of muscle in its wall that allows it to perform mixing or churning movements. Gastric glands produce hydrochloric acid, pepsin, renin, mucus, gastrin, and intrinsic factor. Mucus protects the stomach itself from being digested. 

The tubelike small intestine is suspended from the posterior body wall by the mesentery. Its subdivisions are the duodenum, jejunum, and ileum (Figure 14.4). Food digestion and absorption are completed here. Pancreatic juice and bile enter the duodenum through a sphincter at the distal end of the bile duct. Microvilli, villi, and circular folds increase the surface area of the small intestine for enhanced absorption. 

The large intestine frames the small intestine. Subdivisions are the cecum; appendix; ascending, transverse, and descending colon; sigmoid colon; rectum; anal canal (Figure 14.5). The large intestine delivers undigested food residue (feces) to the body exterior. 

Return to top 

Many accessory organs duct substances into the alimentary tube (Figure 14.6). 

The pancreas is a soft gland lying in the mesentery between the stomach and small intestine. Pancreatic juice contains enzymes (pancreatic amylase: acts on starch; trypsin: acts on protein; lipase: acts on lipids) in an alkaline fluid. 

The liver is a four-lobed organ overlying the stomach. Its digestive function is to produce bile, which it ducts into the small intestine. 

The gallbladder is a muscular sac that stores and concentrates bile. When fat digestion is not occurring, the continuously made bile backs up the cystic duct and enters the gallbladder. 

Salivary glands (three pairs - parotid, submandibular, sublingual) secrete saliva into the oral cavity. Saliva contains mucus and serous fluids. The serous component contains salivary amylase. 

Two sets of teeth are formed. The first set consists of 20 deciduous teeth that begin to appear at 6 months and are lost by 12 years. Permanent teeth (32) begin to replace deciduous teeth around 7 years. A typical tooth consists of crown covered with enamel and root covered with cementum. Most of the tooth is bonelike dentin. The pulp cavity contains blood vessels and nerves. 
Return to top 


Functions of the Digestive System

Foods must be broken down to their building blocks to be absorbed. Building blocks of carbohydrates are simple sugars, or monosaccharides, Building blocks of proteins are amino acids. Building blocks of fats, or lipids, are fatty acids and glycerol. 

Both mechanical (chewing) and chemical food breakdown begin in the mouth. Saliva contains mucus, which helps bind food together into a bolus, and salivary amylase, which begins the chemical breakdown of starch. Saliva is secreted in response to food in the mouth, mechanical pressure, and psychic stimuli. Essentially no food absorption occurs in the mouth. 

Swallowing has two phases: The buccal phase is voluntary; the tongue pushes the bolus into the pharynx. The involuntary pharyngeal-esophageal phase involves the closing off of nasal and respiratory passages and the conduction of food to the stomach by peristalsis. 

When food enters the stomach, gastric secretion is stimulated by vagus nerves and by gastrin (a local hormone). Hydrochloric acid activates the protein-digesting enzyme pepsin, and chemical digestion of proteins begins. Food is also mechanically broken down by the churning activity of stomach muscles. Movement of chyme into the small intestine is controlled by the enterogastric reflex. 

Chemical digestion of fats, proteins, and carbohydrates is completed in the small intestine by intestinal enzymes and, more importantly, pancreatic enzymes. Alkaline pancreatic juice neutralizes acid chyme and provides the proper environment for the operation of enzymes. Both pancreatic Juice (the only source of lipases) and bile (formed by the liver) are necessary for normal fat breakdown and absorption. Bile acts as a fat emulsifier. Secretin and cholecystokinin, hormones produced by the small intestine, stimulate release of bile and pancreatic juice. Segmental movements mix foods; peristaltic movements move foodstuffs along the small intestine. Most nutrient absorption occurs by active transport into the capillary blood of the villi (Figure 14.7). Fats are absorbed by diffusion into both capillary blood and lacteals in the villi. 

The large intestine receives bacteria-laden indigestible food residue. Activities of the large intestine are absorption of water and salts and of vitamins made by resident bacteria. When feces are delivered to the rectum by peristalsis and mass peristalsis. the defecation reflex is initiated. 
Return to top 


Nutrition and Metabolism

Metabolism includes all chemical breakdown (catabolic) and building (anabolic) reactions needed to maintain life (Figure 14.8). 

Carbohydrates, most importantly glucose, are the body's major energy fuel. As glucose is oxidized, carbon dioxide, water, and ATP are formed. The sequential pathways of glucose catabolism are glycolysis, which occurs in the cytosol, and the Krebs cycle and electron transport chain (in the mitochondria). During hypergiycemia, glucose is stored as glycogen or converted to fat. In hypoglycemia, glycogenolysis, gluconeogenesis, and fat breakdown occur to restore normal blood glucose levels. 

Fats insulate the body, protect organs, build some cell structures (membranes and myelin sheaths), and provide reserve energy. When carbohydrates are not available, more fats are oxidized to produce ATP. Excessive fat breakdown causes blood to become acidic. Excess dietary fat is stored in subcutaneous tissue and other fat depots. 

Proteins form the bulk of cell structure and most functional molecules. They are carefully conserved by body cells. Amino acids are actively taken up from blood by tissue cells; those that cannot be made by body cells are called essential amino acids. Amino acids are oxidized to form ATP mainly when other fuel sources are not available. Ammonia, released as amino acids are catabolized, is detoxified by liver cells that combine it with carbon dioxide to form urea. 

The liver is the body's key metabolic organ. Its cells remove nutrients from hepatic portal blood. It performs glycogenesis (glucose converted to and stored as glycogen), glycogenolysis (glycogen broken down into glucose), and gluconeogenesis (formation of glucose from proteins and fats) to maintain homeostasis of blood glucose levels. Its cells make blood proteins and other substances and release them to blood. Fats are burned by liver cells to provide some of their energy (ATP); excesses are stored or released to blood in simpler forms that can be used by other tissue cells. Phagocytic cells remove bacteria from hepatic portal blood. Most cholesterol is made by the liver; cholesterol breakdown products are secreted in bile. Fats and cholesterol are transported in the blood by lipoproteins. LDL's transport cholesterol to body cells; HDL's carry cholesterol to the liver for degradation. Cholesterol is used to make functional molecules and for some structural purposes; it is not used for energy. 

A dynamic balance exists between energy intake and total energy output (heat + work + energy storage). Interference with this balance results in obesity or malnutrition leading to body wasting. 

When the three major types of foods are oxidized for energy, they yield different amounts of energy, Carbohydrates and proteins yield 4 kcal/gram; fats yield 9 kcal/gram. Basal metabolic rate (BMR) is the total amount of energy used by the body when one is in a basal state. Age, sex, body surface area, and amount of thyroxine produced influence BMR. 

Total metabolic rate (TMR) is number of calories used by the body to accomplish all ongoing daily activities. It increases dramatically as muscle activity increases. When TMR equals total caloric intake, weight remains constant. 

As foods are catabolized to form ATP, more than 60 percent of energy released escapes as heat, warming the body. The hypothalamus initiates heat-loss processes (radiation of heat from skin and evaporation of sweat) or heat-promoting processes (vasoconstriction of skin blood vessels and shivering) as necessary to maintain body temperature within normal limits. Fever (hyperthermia) represents body temperature regulated at higher-than-normal levels. 
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Developmental Aspects of the Digestive System and Metabolism

The alimentary tract forms as a hollow tube. Accessory glands form as outpocketings from this tube. 

Common congenital defects include cleft palate, cleft lip, and tracheoesophageal fistula, all of which interfere with normal nutrition. Common inborn errors of metabolism are phenylketonuria (PKU) and cystic fibrosis. 

Various inflammatory conditions plague the digestive system throughout life. Appendicitis is common in adolescents, gastroenteritis and food poisoning can occur at any time (given the proper irritating factors), ulcers and gallbladder problems increase in middle age. Obesity and diabetes mellitus are bothersome during later middle age. 

Efficiency of all digestive system processes decreases in the elderly. Gastrointestinal cancers, such as stomach and colon cancer, appear with increasing frequency in an aging population. 

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The Major Endocrine Organs

Pituitary gland 
The pituitary gland hangs from the base of the brain by a stalk and is enclosed by bone. It consists of a glandular (anterior) portion and a neural (posterior) portion (Figure 9.4). 

Except for growth hormone and prolactin, hormones of the anterior pituitary are all tropic hormones. 



Growth hormone (GH): An anabolic and protein-conserving hormone that promotes total body growth. Its most important effect is on skeletal muscles and bones. Hyposecretion during childhood results in pituitary dwarfism; hypersecretion produces giantism (in childhood) and acromegaly (in adulthood). 

Prolactin (PRL): Stimulates production of breast milk. 

Adrenocorticotropic hormone (ACTH): Stimulates the adrenal cortex to release its hormones. 

Thyroid-stimulating hormone (TSH): Stimulates the thyroid gland to release thyroid hormone. 

Gonadotropic hormones 

Follicle-stimulating hormone (FSH): Beginning at puberty, stimulates follicle development and estrogen production by the female ovaries; promotes sperm production in the male. 

Luteinizing hormone (LH): Beginning at puberty, stimulates ovulation, converts the ruptured ovarian follicle to a corpus luteum, and causes the corpus luteum to produce progesterone; stimulates the male's testes to produce testosterone. 

Releasing and inhibiting hormones made by the hypothalamus regulate release of hormones made by the anterior pituitary. The hypothalamus also makes two hormones that are transported to the posterior pituitary for storage and later release. 

The posterior pituitary stores and releases hypothalamic hormones on command. 


Oxytocin: Stimulates powerful uterine contractions and causes milk ejection in the nursing woman. 

Antidiuretic hormone (ADH): Causes kidney tubule cells to reabsorb and conserve body water and increases blood pressure by constricting blood vessels. Hyposecretion leads to diabetes insipidus. 
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Thyroid gland 

The thyroid gland is located in the anterior throat. 

Thyroid hormone (thyroxine [T4] and triiodothyronine [T3]) is released from the thyroid follicles when blood levels of TSH rise (Figure 9.5). Thyroid hormone is the body's metabolic hormone. It increases the rate at which cells oxidize glucose and is necessary for normal growth and development. Lack of iodine leads to goiter. Hyposecretion of thyroxine results in cretinism in children and myxedema in adults. Hypersecretion results from Graves' disease or other forms of hyperthyroidism. 

Calcitonin is released by C cells surrounding the thyroid follicles in response to high blood levels of calcium (Figure 9.6). It causes calcium to be deposited in bones. 

Parathyroid glands 

The parathyroid glands are four small glands located on the posterior aspect of the thyroid gland. 

Low blood levels of calcium stimulate the parathyroid glands to release parathyroid hormone (PTH). It causes bone calcium to be liberated into the blood. Hyposecretion of PTH results in tetany; hypersecretion leads to extreme bone wasting and fractures. 
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Adrenal glands 

The adrenal glands are paired glands perched on the kidneys. Each gland has two functional endocrine portions, cortex and medulla. 

Three groups of steroid hormones are produced by the adrenal cortex. 

Mineralocorticoids, primarily aldosterone, regulate sodium ion (Na+) and potassium ion (K+) reabsorption by the kidneys (Figure 9.7). Their release is stimulated primarily by low Na+ and/or high K+ levels in blood. 

Glucocorticoids enable the body to resist long-term stress by increasing blood glucose levels and depressing the inflammatory response. 

Sex hormones (mainly male sex hormones) are produced in small amounts throughout life. 

Generalized hypoactivity of the adrenal cortex results in Addison's disease. Hypersecretion can result in hyperaldosteronism, Cushing's disease, and/or masculinization. 

The adrenal medulla produces catecholamines (epinephrine and norepinephrine) in response to sympathetic nervous system stimulation. Its catecholamines enhance and prolong the effects of the fight-or-flight (Sympathetic nervous system) response to short-term stress. Hypersecretion leads to symptoms Typical of sympathetic nervous system overactivity. 
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Pancreatic islets 

Located in the abdomen close to the stomach, the pancreas is both an exocrine and endocrine gland. The endocrine portion (islets) releases insulin and glucagon to blood (Figure 9.8). 

Insulin is released when blood levels of glucose are high. It increases the rate of glucose uptake and metabolism by body cells. Hyposecretion of insulin results in diabetes mellitus, which severely disturbs body metabolism. Cardinal signs are polyuria, polydipsia, and polyphagia. 

Glucagon is released when blood levels of glucose are low. It stimulates the liver to release glucose to blood by accelerating the conversion of glycogen to glucose, thus increasing blood glucose levels. 

The pineal gland, located in the third ventricle of the brain, releases melatonin, which affects biological rhythms and reproductive behavior. 

The thymus gland, located in the upper thorax, functions during youth but atrophies in old age. Its hormone, thymosin, promotes maturation of T lymphocytes, important in body defense. 

Gonads 

The ovaries of the female, located in the pelvic cavity, release two hormones. 

Estrogens: Release of estrogens by ovarian follicles begins at puberty under the influence of FSH. Estrogens stimulate maturation of the female reproductive organs and development of secondary sex characteristics of the female. With progesterone, they cause the menstrual cycle. 

Progesterone: Progesterone is released from the corpus luteum of the ovary in response to high blood levels of LH. It works with estrogens in establishing the menstrual cycle. 


The testes of the male begin to produce testosterone at puberty in response to LH stimulation. Testosterone promotes maturation of the male reproductive organs, male secondary sex characteristics, and production of sperm by the testes. 

Hyposecretion of gonadal hormones results in sterility in both females and males. 
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Other Hormone-Producing Tissues and Organs

The placenta is a temporary organ formed in the uterus of pregnant women. Its primary endocrine role is to produce estrogen and progesterone, which maintain pregnancy and ready breasts for lactation. 

Several organs that are generally nonendocrine in overall function, such as the stomach, small intestine, kidneys, and heart, have cells that secrete hormones. 

Certain cancer cells secrete hormones. 
The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, where attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction. Exceptions to this are the action of cilia, the flagellum on sperm cells, and amoeboid movement of some white blood cells.   

The integrated action of joints, bones, and skeletal muscles produces obvious movements such as walking and running. Skeletal muscles also produce more subtle movements that result in various facial expressions, eye movements, and respiration. 


In addition to movement, muscle contraction also fulfills some other important functions in the body, such as posture, joint stability, and heat production. Posture, such as sitting and standing, is maintained as a result of muscle  contraction. The skeletal muscles are continually making fine adjustments that hold the body in stationary positions. The tendons of many muscles extend over joints and in this way contribute to joint stability. This is particularly evident in the knee and shoulder joints, where muscle tendons are a major factor in stabilizing the joint. Heat production, to maintain body temperature, is an important by-product of muscle metabolism. Nearly 85 percent of the heat produced in the body is the result of muscle contraction. 



A whole skeletal muscle is considered an organ of the muscular system. Each organ or muscle consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue.

Skeletal muscles vary considerably in size, shape, and arrangement of fibers. They range from extremely tiny strands such as the stapedium muscle of the middle ear to large masses such as the muscles of the thigh. Some skeletal muscles are broad in shape and some narrow. In some muscles the fibers are parallel to the long axis of the muscle, in some they converge to a narrow attachment, and in some they are oblique.


 

Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium. Fascia, connective tissue outside the epimysium, surrounds and separates the muscles. Portions of the epimysium project inward to divide the muscle into compartments. Each compartment contains a bundle of muscle fibers. Each bundle of muscle fiber is called a fasciculus and is surrounded by a layer of connective tissue called the perimysium. Within the fasciculus, each individual muscle cell, called a muscle fiber, is surrounded by connective tissue called the endomysium. 

Skeletal muscle cells (fibers), like other body cells, are soft and fragile. The connective tissue covering furnish support and protection for the delicate cells and allow them to withstand the forces of contraction. The coverings also provide pathways for the passage of blood vessels and nerves.

Commonly, the epimysium, perimysium, and endomysium extend beyond the fleshy part of the muscle, the belly or gaster, to form a thick ropelike tendon or a broad, flat sheet-like aponeurosis. The tendon and aponeurosis form indirect attachments from muscles to the periosteum of bones or to the connective tissue of other muscles. Typically a muscle spans a joint and is attached to bones by tendons at both ends. One of the bones remains relatively fixed or stable while the other end moves as a result of muscle contraction. 

Skeletal muscles have an abundant supply of blood vessels and nerves. This is directly related to the primary function of skeletal muscle, contraction. Before a skeletal muscle fiber can contract, it has to receive an impulse from a nerve cell. Generally, an artery and at least one vein accompany each nerve that penetrates the epimysium of a skeletal muscle. Branches of the nerve and blood vessels follow the connective tissue components of the muscle of a nerve cell and with one or more minute blood vessels called capillaries. 


In the body, there are three types of muscle: skeletal (striated), smooth, and cardiac.

Skeletal Muscle 
Skeletal muscle, attached to bones, is responsible for skeletal movements. The peripheral portion of the central nervous system (CNS) controls the skeletal muscles. Thus, these muscles are under conscious, or voluntary, control. The basic unit is the muscle fiber with many nuclei. These muscle fibers are striated (having transverse streaks) and each acts independently of neighboring muscle fibers. 


Smooth Muscle 
Smooth muscle, found in the walls of the hollow internal organs such as blood vessels, the gastrointestinal tract, bladder, and uterus, is under control of the autonomic nervous system. Smooth muscle cannot be controlled consciously and thus acts involuntarily. The non-striated (smooth) muscle cell is spindle-shaped and has one central nucleus. Smooth muscle contracts slowly and rhythmically. 

Cardiac Muscle 
Cardiac muscle, found in the walls of the heart, is also under control of the autonomic nervous system. The cardiac muscle cell has one central nucleus, like smooth muscle, but it also is striated, like skeletal muscle. The cardiac muscle cell is rectangular in shape. The contraction of cardiac muscle is involuntary, strong, and rhythmical. 

Smooth and cardiac muscle will be discussed in detail with respect to their appropriate systems. This unit mainly covers the skeletal muscular system.


 
 
There are more than 600 muscles in the body, which together account for about 40 percent of a person's weight. 

Most skeletal muscles have names that describe some feature of the muscle. Often several criteria are combined into one name. Associating the muscle's characteristics with its name will help you learn and remember them. The following are some terms relating to muscle features that are used in naming muscles. 

Size: vastus (huge); maximus (large); longus (long); minimus (small); brevis (short). 
Shape: deltoid (triangular); rhomboid (like a rhombus with equal and parallel sides); latissimus (wide); teres (round); trapezius (like a trapezoid, a four-sided figure with two sides parallel). 
Direction of fibers: rectus (straight); transverse (across); oblique (diagonally); orbicularis (circular). 
Location: pectoralis (chest); gluteus (buttock or rump); brachii (arm); supra- (above); infra- (below); sub- (under or beneath); lateralis (lateral). 
Number of origins: biceps (two heads); triceps (three heads); quadriceps (four heads). 
Origin and insertion: sternocleidomastoideus (origin on the sternum and clavicle, insertion on the mastoid process); brachioradialis (origin on the brachium or arm, insertion on the radius). 
Action: abductor (to abduct a structure); adductor (to adduct a structure); flexor (to flex a structure); extensor (to extend a structure); levator (to lift or elevate a structure); masseter (a chewer). 
Listed below are some significant and obvious muscles arranged in groups according to location and/or function. Click one of the hyper-links to explore a specific muscle group listed below. 

Muscles of the Head and Neck 
Muscles of the Trunk 
Muscles of the Upper Extremity 
Muscles of the Lower Extremity 

 Muscular System: Unit Review and Quiz 
  

Unit Review 
Here is what we have learned from this unit: 

One of the most predominant characteristics of skeletal muscle tissue is its contractility and nearly all movement in the body is the result of muscle contraction. 
Four functions of muscle contraction are movement, posture, joint stability, and heat production. 
Three types of muscle are skeletal, smooth, and cardiac. 
Each muscle fiber is surrounded by endomysium. The fibers are collected into bundles covered by perimysium. Many bundles, or fasciculi, are wrapped together by the epimysium to form a whole muscle. 
Muscles are attached to bones by tendons. 
Muscle features such as size, shape, direction of fibers, location, number of origin, origin and insertion, and action are often used in naming muscles. 
Four major muscle groups of the body include: 
Muscles of the head and neck; 
Muscles of the trunk; 
Muscles of the upper extremity; and 
Muscles of the lower extremity. 
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Unit 5 – The Nervous System Review

Here is what we have learned from this unit:
•The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory.
•The various activities of the nervous system can be grouped together as three general, overlapping functions: sensory, integrative, and motor.
•Neurons are the nerve cells that transmit impulses. Supporting cells are neuroglia.
•The three components of a neuron are a cell body or soma, one or more afferent processes called dendrites, and a single efferent process called an axon.
•The central nervous system consists of the brain and spinal cord. Cranial nerves, spinal nerves, and ganglia make up the peripheral nervous system.
•The afferent division of the peripheral nervous system carries impulses to the CNS; the efferent division carries impulses away from the CNS.
•There are three layers of meninges around the brain and spinal cord. The outer layer is dura mater, the middle layer is arachnoid, and the innermost layer is pia mater.
•The spinal cord functions as a conduction pathway and as a reflex center. Sensory impulses travel to the brain on ascending tracts in the cord. Motor impulses travel on descending tracts.
The organs of the peripheral nervous system are the nerves and ganglia. Nerves are bundles of nerve fibers, much like muscles are bundles of muscle fibers. Cranial nerves and spinal nerves extend from the CNS to peripheral organs such as muscles and glands. Ganglia are collections, or small knots, of nerve cell bodies outside the CNS.

The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent (motor) division. The afferent or sensory division transmits impulses from peripheral organs to the CNS. The efferent or motor division transmits impulses from the CNS out to the peripheral organs to cause an effect or action. Click here to learn more about PNS.

Finally, the efferent or motor division is again subdivided into the somatic nervous system and the autonomic nervous system. The somatic nervous system, also called the somatomotoror somatic efferent nervous system, supplies motor impulses to the skeletal muscles. Because these nerves permit conscious control of the skeletal muscles, it is sometimes called the voluntary nervous system. The autonomic nervous system, also called the visceral efferent nervous system, supplies motor impulses to cardiac muscle, to smooth muscle, and to glandular epithelium. It is further subdivided into sympathetic and parasympathetic divisions. Because the autonomic nervous system regulates involuntary or automatic functions, it is called the involuntary nervous system.
Urinary System
Kidneys
Ureters, Urinary Bladder, and Urethra
Developmental Aspects of the Urinary System 
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Kidneys

The paired kidneys are retroperitoneal in the superior lumbar region. Each kidney has a medial indentation (hilus), where the renal artery, renal vein (Figure 15.1). and ureter are seen. Each kidney is enclosed in a tough fibrous capsule. A fatty cushion holds the kidneys against the trunk wall. 

A longitudinal section of a kidney reveals an outer cortex, deeper medulla, and medial pelvis. Extensions of the pelvis (calyces) surround the tips of medullary pyramids and collect urine draining from them. 

The renal artery, which enters the kidney, breaks up into segmental, lobar, and then interlobar arteries that travel outward through the medulla. Interlobar arteries split into arcuate arteries, which branch to produce interiobular arteries, which serve the cortex. 

Nephrons are structural and functional units of the kidneys (Figure 15.2). Each consists of a glomerulus and a renal tubule. Subdivisions of the renal tubule (from the glomerulus) are glomerular capsule, proximal convoluted tubule, loop of Henle, and distal convoluted tubule. A second (peritubular) capillary bed is also associated with each nephron. 

Nephron functions include filtration, reabsorption, and secretion (Figure 15.3). Filtrate formation is the role of the high-pressure glomerulus. Filtrate is essentially plasma without blood proteins. In reabsorption, done by tubule cells, needed substances are removed from filtrate (amino acids, glucose, water, some ions) and returned to blood. The tubule cells also secrete additional substances into nitrate. Secretion is important to rid the body of drugs and excess ions (potassium, hyrdogen, and ammonia) and to maintain acid-base balance of blood. 

Blood composition depends on diet, cellular metabolism, and urinary output. To maintain blood composition, the kidneys must: 

Allow nitrogen-containing wastes (urea, ammonia, creatinine, uric acid) to go out in the urine. 

Maintain water and electrolyte balance by absorbing more or less water and reclaiming ions in response to hormonal signals. ADH, which acts on the collecting ducts, increases water reabsorption and conserves body water. Aldosterone increases reabsorption of sodium and water and decreases potassium reabsorption. 

Maintain acid-base balance by actively secreting bicarbonate ions (and retaining H+) and by absorbing bicarbonate ions (and secreting H+. Chemical buffers tie up excess H+ or bases temporarily: respiratory centers modify blood pH by retaining C02 (decreases pH) or by eliminating more CO2 from the blood (increases blood pH). Only the kidney can remove metabolic acids and excess bases from the body. 

Urine is clear, yellow, and usually slightly acid, but its pH value varies widely. Substances normally found in urine are nitrogenous wastes, water, various ions (always sodium and potassium). Substances normally absent from urine include glucose, blood proteins, blood, pus (WBC's), bile. 
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Ureters, Urinary Bladder, and Urethra

The ureters are slender tubes running from each kidney to the bladder (Figure 15.4). They conduct urine by peristalsis from kidney to bladder. 

The bladder is a muscular sac posterior to the pubic symphysis. It has two inlets (ureters) and one outlet (urethra). In males, the prostate gland surrounds its outlet. The function of the bladder is to store urine. 

The urethra is a tube that leads urine from the bladder to the body exterior. In females, it is 3-4 cm long and conducts only urine. In males, it is 20 cm long and conducts both urine and sperm. The internal sphincter of smooth muscle is at the bladder-urethra junction. The external sphincter of skeletal muscle is located more inferiorly. 

Micturition is emptying of the bladder. The micturition reflex causes the involuntary internal sphincter to open when stretch receptors in the bladder wall are stimulated. Since the external sphincter is voluntarily controlled, micturition can ordinarily be temporarily delayed. Incontinence is the inability to control micturition. 
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Developmental Aspects of the Urinary System

The kidneys begin to develop in the first few weeks of embryonic life and are excreting urine by the third month, 

Common congenital abnormalities include polycystic kidney and hypospadias. 

Common urinary system problems in children and young to middle-aged adults are infections caused by fecal microorganisms, sexually transmitted disease-causing microorganisms, and streptococcus. 

Renal failure is an uncommon, but extremely serious, problem in which kidneys are unable to concentrate urine, and dialysis must be done to maintain chemical homeostasis of blood. 

With age, filtration rate decreases and tubule cells become less efficient at concentrating urine, leading to urgency, frequency, and incontinence. In males, urinary retention is another common problem. 

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 Lesson 1
INTRODUCTION

9-1. DEFINITION

The human reproduction system is a collection of organs for the production of offspring. Thus, succeeding generations are provided for the continuation of the species.

9-2. TWO DISTINCT SEXES

In humans there are two distinctly separate sexes, male and female. The presence of different anatomical forms of the two sexes is called sexual dimorphism.

DI = two
MORPH = body form
SEXUAL = by virtue of sex

The contribution of hereditary materials by two parents increases the chances for improved genetic recombinations.

9-3. SEX HORMONES

Sex hormones are body chemicals associated with sex and sexual development. They belong to a chemical group called steroids. Sex hormones are formed primarily in two types of organs: the gonads and the adrenal cortex. (The adrenal cortex is the outer layer of the adrenal gland, which rests upon each kidney). The sex hormones of the female are called estrogens and progesterone. The sex hormones of the male are called androgens.

9-4. MAJOR ORGAN SUBGROUPS

In both males and females, the organs of the reproductive system can be grouped according to function. These subgroups are the primary sex organs (gonads), the secondary sex organs, and the secondary sexual characteristics.

9-5. EXTERNAL GENITALIA

In both sexes, there are certain structures at the surface known as the external genitalia.

9-6. COMMON EMBRYONIC ORGANS

In male and female embryos, there is a common origin of the organs of the reproductive system. (The organs of the urinary system share this common origin). The importance of this common origin is that, under certain conditions, females may develop with males characteristics, males may develop with female characteristics, and even true intersexes may occur. (True intersexes possess both male and female gonadal tissue.)

9-7. SEX DETERMINATION

At the moment the egg is fertilized by the sperm, the new genetic combination determines whether the individual will be male or female. Later in development, however, sex hormones play an important role in the production of sexual organs and characteristics.
 
The lymphatic system

http://www.cancerhelp.org.uk/help/default.asp?page=117#what_is_



This page tells you about the lymphatic system.  You can click on these links to go straight to a particular section on

What is the lymphatic system?          
Lymph glands          
Other organs that are part of the lymphatic system          
What does the lymphatic system do?          
Draining fluid into the bloodstream          
Filtering lymph          
Fighting infection
What is the lymphatic system?
The lymphatic system is a system of thin tubes that runs throughout the body. These tubes are called 'lymph vessels'. You may also hear them called 'lymphatic vessels'. 



The lymphatic system is like the blood circulation - the tubes branch through all parts of the body like the arteries and veins that carry blood. Except that the lymphatic system carries a colourless liquid called 'lymph'. 

Lymph is a clear fluid that circulates around the body tissues. It contains a high number of lymphocytes (white blood cells). Plasma leaks out of the capillaries to surround and bathe the body tissues. This then drains into the lymph vessels. 

 


The fluid, now called lymph, then flows through the lymphatic system to the biggest lymph vessel - the thoracic duct. The thoracic duct then empties back into the blood circulation. 



Lymph glands
Along the lymph vessels are small bean-shaped lymph glands or 'nodes'. You can probably feel some of your lymph nodes. 

 

There are lymph nodes 


Under your arms, in your armpits                
In each groin (at the top of your legs)                
In your neck 
There are also lymph nodes that you cannot feel in 


Your abdomen                          
Your pelvis          
Your chest 
Other organs that are part of the lymphatic system
The lymphatic system includes other body organs.  These are the


Spleen        
Thymus        
Tonsils        
Adenoids
The spleen is under your ribs on the left side of your body. The spleen works as a filter of lymph fluid. 

The thymus is a small gland under your breast bone. The thymus helps to produce white blood cells.  It is usually most active in teenagers and shrinks in adulthood.
 
The tonsils are two glands in the back of your throat. The tonsils and adenoids (also called the 'nasopharyngeal' tonsils) help to protect the entrance to the digestive system and the lungs from bacteria and viruses. 

 

The adenoids are at the back of your nose, where it meets the back of your throat. 

What does the lymphatic system do? 
The lymphatic system does several jobs in the body.  It 

Drains fluid back into the bloodstream from the tissues  
Filters lymph  
Filters the blood  
Fights infections
Draining fluid into the bloodstream
As the blood circulates, fluid leaks out into the body tissues. This fluid is important because it carries food to the cells and waste products back to the bloodstream. The leaked fluid drains into the lymph vessels. It is carried through the lymph vessels to the base of the neck where it is emptied back into the bloodstream. This circulation of fluid through the body is going on all the time. 

Filtering lymph
The lymph nodes filter the lymph as it passes through.  White blood cells attack any bacteria or viruses they find in the lymph as it flows through the lymph nodes.  If cancer cells break away from a tumour, they often become stuck in the nearest lymph nodes.  This is why doctors check the lymph nodes first when they are working out how far a cancer has grown or spread.

Filtering the blood
This is the job of the spleen.  It filters the blood to take out all the old worn out red blood cells and then destroys them.  They are replaced by new red blood cells that have been made in the bone marrow.  The spleen also filters out bacteria, viruses and other foreign particles found in the blood.  White blood cells in the spleen attack bacteria and viruses as they pass through.

Fighting infection
When people say "I'm not well, my glands are up" they are really saying they have swollen lymph nodes because they have an infection. The lymphatic system helps fight infection in many ways such as 

Helping to make special white blood cells (lymphocytes) that produce antibodies                
Having other blood cells called macrophages inside the lymph nodes which swallow up and kill any foreign particles, for example germs 
This function of the lymphatic system is really part of the immune system. There is more about this in the the immune system section of CancerHelp UK. 








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CancerHelp UK is not designed to provide medical advice or professional services and is intended to be for educational use only. The information provided through CancerHelp UK is not a substitute for professional care and should not be used for diagnosing or treating a health problem or a disease. If you have, or suspect you may have, a health problem you should consult your doctor. 

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 Lesson 1
GENERAL

4-1. INTRODUCTION

The skeleton forms the framework for the human body. It is composed of individual bones. These bones meet (are articulated with) each other at joints.

4-2. GENERAL FUNCTIONS

a.      Support. In general, the skeleton supports the body.

b.      Motion and Locomotion. Because of the joints and the attached skeletal muscles, the parts of the body can move with respect to each other (motion). Also, because of such linkages in the lower members, the entire body can be moved from place to place (locomotion).

c.      Protection. Certain parts of the skeleton are structured to protect vital organs.

d.      Hematopoiesis. The skeleton is also involved in formation of blood (hematopoiesis) cells.

e.      Storage. Moreover, the skeleton stores various minerals.
 
 Nervous System
Unit Goal
Users will gain a basic knowledge of the nervous system in terms of its structure, functions, and classification.

Objectives

After completing this unit, users will be able to:
1.name the three general, overlapping functions performed by the nervous system;
2.list the two main types of cells in nerve tissue and describe their functions; and
3.name the two subdivisions of the nervous system and describe the differences of their structural and functional characteristics.

The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory. Together with the endocrine system, the nervous system is responsible for regulating and maintaining homeostasis.
Through its receptors, the nervous system keeps us in touch with our environment, both external and internal.

Like other systems in the body, the nervous system is composed of organs, principally the brain, spinal cord, nerves, and ganglia. These, in turn, consist of various tissues, including nerve, blood, and connective tissue. Together these carry out the complex activities of the nervous system.


The various activities of the nervous system can be grouped together as three general, overlapping functions:

Sensory
Integrative
Motor

Millions of sensory receptors detect changes, called stimuli, which occur inside and outside the body. They monitor such things as temperature, light, and sound from the external environment. Inside the body, the internal environment, receptors detect variations in pressure, pH, carbon dioxide concentration, and the levels of various electrolytes. All of this gathered information is called sensory input.

Sensory input is converted into electrical signals called nerve impulses that are transmitted to the brain. There the signals are brought together to create sensations, to produce thoughts, or to add to memory; Decisions are made each moment based on the sensory input. This is integration.

Based on the sensory input and integration, the nervous system responds by sending signals to muscles, causing them to contract, or to glands, causing them to produce secretions. Muscles and glands are called effectors because they cause an effect in response to directions from the nervous system. This is the motor output or motor function.

Although the nervous system is very complex, there are only two main types of cells in nerve tissue. The actual nerve cell is the neuron. It is the "conducting" cell that transmits impulses and the structural unit of the nervous system. The other type of cell is neuroglia, or glial, cell. The word "neuroglia" means "nerve glue." These cells are nonconductive and provide a support system for the neurons. They are a special type of "connective tissue" for the nervous system.

Neurons
Neurons, or nerve cells, carry out the functions of the nervous system by conducting nerve impulses. They are highly specialized and amitotic. This means that if a neuron is destroyed, it cannot be replaced because neurons do not go through mitosis. The image below illustrates the structure of a typical neuron.



Each neuron has three basic parts: cell body (soma)], one or more [[dendrites, and a single axon.

Cell Body
In many ways, the cell body is similar to other types of cells. It has a nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles. It lacks centrioles, however. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell.

Dendrites
Dendrites and axons are cytoplasmic extensions, or processes, that project from the cell body. They are sometimes referred to as fibers. Dendrites are usually, but not always, short and branching, which increases their surface area to receive signals from other neurons. The number of dendrites on a neuron varies. They are called afferent processes because they transmit impulses to the neuron cell body. There is only one axon that projects from each cell body. It is usually elongated and because it carries impulses away from the cell body, it is called an efferent process.

Axon
An axon may have infrequent branches called axon collaterals. Axons and axon collaterals terminate in many short branches or telodendria. The distal ends of the telodendria are slightly enlarged to form synaptic bulbs. Many axons are surrounded by a segmented, white, fatty substance called myelin or the myelin sheath. Myelinated fibers make up the white matter in the CNS, while cell bodies and unmyelinated fibers make the gray matter. The unmyelinated regions between the myelin segments are called the nodes of Ranvier .

In the peripheral nervous system, the myelin is produced by Schwann cells. The cytoplasm, nucleus, and outer cell membrane of the Schwann cell form a tight covering around the myelin and around the axon itself at the nodes of Ranvier. This covering is the neurilemma, which plays an important role in the regeneration of nerve fibers. In the CNS, oligodendrocytes produce myelin, but there is no neurilemma, which is why fibers within the CNS do not regenerate.

Functionally, neurons are classified as afferent, efferent, or interneurons (association neurons) according to the direction in which they transmit impulses relative to the central nervous system. Afferent, or sensory, neurons carry impulses from peripheral sense receptors to the CNS. They usually have long dendrites and relatively short axons. Efferent, or motor, neurons transmit impulses from the CNS to effector organs such as muscles and glands. Efferent neurons usually have short dendrites and long axons. Interneurons, or association neurons, are located entirely within the CNS in which they form the connecting link between the afferent and efferent neurons. They have short dendrites and may have either a short or long axon.

Neuroglia
Neuroglia cells do not conduct nerve impulses, but instead, they support, nourish, and protect the neurons. They are far more numerous than neurons and, unlike neurons, are capable of mitosis.

Tumors
Schwannomas are benign tumors of the peripheral nervous system which commonly occur in their sporadic, solitary form in otherwise normal individuals. Rarely, individuals develop multiple schwannomas arising from one or many elements of the peripheral nervous system.

Commonly called a Morton's Neuroma, this problem is fairly common benign nerve growth and begins when the outer coating of a nerve in your foot thickens. This thickening is caused by irritation of branches of the medial and lateral plantar nerves that results when two bones repeatedly rub together.



Although terminology seems to indicate otherwise, there is really only one nervous system in the body. Although each subdivision of the system is also called a "nervous system," all of these smaller systems belong to the single, highly integrated nervous system. Each subdivision has structural and functional characteristics that distinguish it from the others. The nervous system as a whole is divided into two subdivisions: the ][central nervous system (CNS}]] and the peripheral nervous system (PNS).

The Central Nervous System

The brain and spinal cord are the organs of the central nervous system. Because they are so vitally important, the brain and spinal cord, located in the dorsal body cavity, are encased in bone for protection. The brain is in the cranial vault, and

the spinal cord is in the vertebral canal of the vertebral column. Although considered to be two separate organs, the brain and spinal cord are continuous at the foramen magnum. Click here to learn more about the CNS.

The Peripheral Nervous System

The organs of the peripheral nervous system are the nerves and ganglia. Nerves are bundles of nerve fibers, much like muscles are bundles of muscle fibers. Cranial nerves and spinal nerves extend from the CNS to peripheral organs such as muscles and glands. Ganglia are collections, or small knots, of nerve cell bodies outside the CNS.

The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent (motor) division. The afferent or sensory division transmits impulses from peripheral organs to the CNS. The efferent or motor division transmits impulses from the CNS out to the peripheral organs to cause an effect or action. Click here to learn more about PNS.

Finally, the efferent or motor division is again subdivided into the somatic nervous system and the autonomic nervous system. The somatic nervous system, also called the somatomotoror somatic efferent nervous system, supplies motor impulses to the skeletal muscles. Because these nerves permit conscious control of the skeletal muscles, it is sometimes called the voluntary nervous system. The autonomic nervous system, also called the visceral efferent nervous system, supplies motor impulses to cardiac muscle, to smooth muscle, and to glandular epithelium. It is further subdivided into sympathetic and parasympathetic divisions. Because the autonomic nervous system regulates involuntary or automatic functions, it is called the involuntary nervous system.














The Nervous System Review

Here is what we have learned from this unit:
•The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory.
•The various activities of the nervous system can be grouped together as three general, overlapping functions: sensory, integrative, and motor.
•Neurons are the nerve cells that transmit impulses. Supporting cells are neuroglia.
•The three components of a neuron are a cell body or soma, one or more afferent processes called dendrites, and a single efferent process called an axon.
•The central nervous system consists of the brain and spinal cord. Cranial nerves, spinal nerves, and ganglia make up the peripheral nervous system.
•The afferent division of the peripheral nervous system carries impulses to the CNS; the efferent division carries impulses away from the CNS.
•There are three layers of meninges around the brain and spinal cord. The outer layer is dura mater, the middle layer is arachnoid, and the innermost layer is pia mater.
•The spinal cord functions as a conduction pathway and as a reflex center. Sensory impulses travel to the brain on ascending tracts in the cord. Motor impulses travel on descending tracts.



Nervous System
Unit Goal
Users will gain a basic knowledge of the nervous system in terms of its structure, functions, and classification.
Objectives
After completing this unit, users will be able to:
1. name the three general, overlapping functions performed by the nervous system;
2. list the two main types of cells in nerve tissue and describe their functions; and
3. name the two subdivisions of the nervous system and describe the differences of their structural and functional characteristics.
The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory. Together with the endocrine system, the nervous system is responsible for regulating and maintaining homeostasis.
Through its receptors, the nervous system keeps us in touch with our environment, both external and internal.

Like other systems in the body, the nervous system is composed of organs, principally the brain, spinal cord, nerves, and ganglia. These, in turn, consist of various tissues, including nerve, blood, and connective tissue. Together these carry out the complex activities of the nervous system.


The various activities of the nervous system can be grouped together as three general, overlapping functions:

Sensory
Integrative
Motor
Millions of sensory receptors detect changes, called stimuli, which occur inside and outside the body. They monitor such things as temperature, light, and sound from the external environment. Inside the body, the internal environment, receptors detect variations in pressure, pH, carbon
dioxide concentration, and the levels of various electrolytes. All of this gathered information is called sensory input.
Sensory input is converted into electrical signals called nerve impulses that are transmitted to the brain. There the signals are brought together to create sensations, to produce thoughts, or to add to memory; Decisions are made each moment based on the sensory input. This is integration.

Based on the sensory input and integration, the nervous system responds by sending signals to muscles, causing them to contract, or to glands, causing them to produce secretions. Muscles and glands are called effectors because they cause an effect in response to directions from the nervous system. This is the motor output or motor function.

Although the nervous system is very complex, there are only two main types of cells in nerve tissue. The actual nerve cell is the neuron. It is the "conducting" cell that transmits impulses and the structural unit of the nervous system. The other type of cell is neuroglia, or glial, cell. The word "neuroglia" means "nerve glue." These cells are nonconductive and provide a support system for the neurons. They are a special type of "connective tissue" for the nervous system.

Neurons
Neurons, or nerve cells, carry out the functions of the nervous system by conducting nerve impulses. They are highly specialized and amitotic. This means that if a neuron is destroyed, it cannot be replaced because neurons do not go through mitosis. The image below illustrates the structure of a typical neuron.



Each neuron has three basic parts: cell body (soma), one or more dendrites, and a single axon.

Cell Body
In many ways, the cell body is similar to other types of cells. It has a nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles. It lacks centrioles, however. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell.

Dendrites
Dendrites and axons are cytoplasmic extensions, or processes, that project from the cell body. They are sometimes referred to as fibers. Dendrites are usually, but not always, short and branching, which increases their surface area to receive signals from other neurons. The number of dendrites on a neuron varies. They are called afferent processes because they transmit impulses to the neuron cell body. There is only one axon that projects from each cell body. It is usually elongated and because it carries impulses away from the cell body, it is called an efferent process.

Axon
An axon may have infrequent branches called axon collaterals. Axons and axon collaterals terminate in many short branches or telodendria. The distal ends of the telodendria are slightly enlarged to form synaptic bulbs. Many axons are surrounded by a segmented, white, fatty substance called myelin or the myelin sheath. Myelinated fibers make up the white matter in the CNS, while cell bodies and unmyelinated fibers make the gray matter. The unmyelinated regions between the myelin segments are called the nodes of Ranvier.

In the peripheral nervous system, the myelin is produced by Schwann cells. The cytoplasm, nucleus, and outer cell membrane of the Schwann cell form a tight covering around the myelin and around the axon itself at the nodes of Ranvier. This covering is the neurilemma, which plays an important role in the regeneration of nerve fibers. In the CNS, oligodendrocytes produce myelin, but there is no neurilemma, which is why fibers within the CNS do not regenerate.

Functionally, neurons are classified as afferent, efferent, or interneurons (association neurons) according to the direction in which they transmit impulses relative to the central nervous system. Afferent, or sensory, neurons carry impulses from peripheral sense receptors to the CNS. They usually have long dendrites and relatively short axons. Efferent, or motor, neurons transmit impulses from the CNS to effector organs such as muscles and glands. Efferent neurons usually have short dendrites and long axons. Interneurons, or association neurons, are located entirely within the CNS in which they form the connecting link between the afferent and efferent neurons. They have short dendrites and may have either a short or long axon.

Neuroglia
Neuroglia cells do not conduct nerve impulses, but instead, they support, nourish, and protect the neurons. They are far more numerous than neurons and, unlike neurons, are capable of mitosis.

Tumors
Schwannomas are benign tumors of the peripheral nervous system which commonly occur in their sporadic, solitary form in otherwise normal individuals. Rarely, individuals develop multiple schwannomas arising from one or many elements of the peripheral nervous system.

Commonly called a Morton's Neuroma, this problem is fairly common benign nerve growth and begins when the outer coating of a nerve in your foot thickens. This thickening is caused by irritation of branches of the medial and lateral plantar nerves that results when two bones repeatedly rub together.


Although terminology seems to indicate otherwise, there is really only one nervous system in the body. Although each subdivision of the system is also called a "nervous system," all of these smaller systems belong to the single, highly integrated nervous system. Each subdivision has structural and functional characteristics that distinguish it from the others. The nervous system as a whole is divided into two subdivisions: the central nervous system (CNS) and the peripheral nervous system (PNS).

The Central Nervous System
The brain and spinal cord are the organs of the central nervous system. Because they are so vitally important, the brain and spinal cord, located in the dorsal body cavity, are encased in bone for protection. The brain is in the cranial vault, and

the spinal cord is in the vertebral canal of the vertebral column. Although considered to be two separate organs, the brain and spinal cord are continuous at the foramen magnum. Click here to learn more about the CNS.
The Peripheral Nervous System
The organs of the peripheral nervous system are the nerves and ganglia. Nerves are bundles of nerve fibers, much like muscles are bundles of muscle fibers. Cranial nerves and spinal nerves extend from the CNS to peripheral organs such as muscles and glands. Ganglia are collections, or small knots, of nerve cell bodies outside the CNS.

The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent (motor) division. The afferent or sensory division transmits impulses from peripheral organs to the CNS. The efferent or motor division transmits impulses from the CNS out to the peripheral organs to cause an effect or action. Click here to learn more about PNS.

Finally, the efferent or motor division is again subdivided into the somatic nervous system and the autonomic nervous system. The somatic nervous system, also called the somatomotor or somatic efferent nervous system, supplies motor impulses to the skeletal muscles. Because these nerves permit conscious control of the skeletal muscles, it is sometimes called the voluntary nervous system. The autonomic nervous system, also called the visceral efferent nervous system, supplies motor impulses to cardiac muscle, to smooth muscle, and to glandular epithelium. It is further subdivided into sympathetic and parasympathetic divisions. Because the autonomic nervous system regulates involuntary or automatic functions, it is called the involuntary nervous system.












Unit 5 – The Nervous System Review
Here is what we have learned from this unit:
• The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory.
• The various activities of the nervous system can be grouped together as three general, overlapping functions: sensory, integrative, and motor.
• Neurons are the nerve cells that transmit impulses. Supporting cells are neuroglia.
• The three components of a neuron are a cell body or soma, one or more afferent processes called dendrites, and a single efferent process called an axon.
• The central nervous system consists of the brain and spinal cord. Cranial nerves, spinal nerves, and ganglia make up the peripheral nervous system.
• The afferent division of the peripheral nervous system carries impulses to the CNS; the efferent division carries impulses away from the CNS.
• There are three layers of meninges around the brain and spinal cord. The outer layer is dura mater, the middle layer is arachnoid, and the innermost layer is pia mater.
• The spinal cord functions as a conduction pathway and as a reflex center. Sensory impulses travel to the brain on ascending tracts in the cord. Motor impulses travel on descending tracts.





Glial cells, commonly called neuroglia or simply glia (greek for "glue"), are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system. In the human brain, glia are estimated to outnumber neurons by about 10 to 1.[1]

Glial cells provide support and protection for neurons, the other main type of cell in the central nervous system. They are thus known as the "glue" of the nervous system. The four main functions of glial cells are to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy pathogens and remove dead neurons.

Contents [hide]
1 Function of the glial cell
2 Types of glia
2.1 Microglia
2.2 Macroglia
3 Capacity to divide
4 Embryological development
5 History
6 Additional images
7 References
8 External links



[edit] Function of the glial cell
Some glia function primarily as physical support for neurons. Others regulate the internal environment of the brain, especially the fluid surrounding neurons and their synapses, and provide nutrition to nerve cells. Glia have important developmental roles, guiding migration of neurons in early development, and producing molecules that modify the growth of axons and dendrites. Recent findings in the hippocampus and cerebellum have indicated that glia are also active participants in synaptic transmission, regulating clearance of neurotransmitter from the synaptic cleft, releasing factors such as ATP which modulate presynaptic function, and even releasing neurotransmitters themselves. Unlike the neuron, which is amitotic, glia are capable of mitosis.

Traditionally glia had been thought to lack certain features of neurons. For example, glia were not believed to have chemical synapses or to release neurotransmitters. They were considered to be the passive bystanders of neural transmission. However, recent studies disproved this. For example, astrocytes are crucial in clearance of neurotransmitter from within the synaptic cleft, which provides distinction between arrival of action potentials and prevents toxic build up of certain neurotransmitters such as glutamate (excitotoxicity). Furthermore, at least in vitro, astrocytes can release neurotransmitter glutamate in response to certain stimulation. Another unique type of glia, the oligodendrocyte precursor cells or OPCs, have very well defined and functional synapses from at least two major groups of neurons. The only notable differences between neurons and glia, by modern scrutiny, are the ability to generate action potentials and the polarity of neurons, namely the axons and dendrites which glia lack.

It is inappropriate nowadays to consider glia as 'glue' in the nervous system as the name implies but more of a partner to neurons. They are also crucial in the development of the nervous system and in processes such as synaptic plasticity and synaptogenesis. Glia have a role in the regulation of repair of neurons after injury. In the CNS glia suppress repair. Astrocytes enlarge and proliferate to form a scar and produce myelin and inhibitory molecules that inhibit regrowth of a damaged or severed axon. In the PNS Schwann cells promote repair. After axon injury Schwann cells regress to an earlier developmental state to encourage regrowth of the axon. This difference between PNS and CNS raises hopes for the regeneration of nervous tissue in the CNS, for example a spinal cord injury or severance.


[edit] Types of glia

[edit] Microglia
For more details on this topic, see Microglia.
Microglia are specialized macrophages capable of phagocytosis that protect neurons of the central nervous system. Though not technically glia because they are derived from hemopoietic precursors rather than ectodermal tissue, they are commonly categorized as such because of their supportive role to neurons.

These cells comprise approximately 15% of the total cells of the central nervous system. They are found in all regions of the brain and spinal cord. Microglial cells are small relative to macroglial cells, with changing shapes and oblong nuclei. They are mobile within the brain and multiply when the brain is damaged. In the healthy central nervous system, microglia processes constantly sample all aspects of their environment (neurons, macroglia and blood vessels).


[edit] Macroglia
Location Name Description
CNS Astrocytes The most abundant type of glial cell, astrocytes (also called astroglia) have numerous projections that anchor neurons to their blood supply. They regulate the external chemical environment of neurons by removing excess ions, notably potassium, and recycling neurotransmitters released during synaptic transmission. The current theory suggests that astrocytes may be the predominant "building blocks" of the blood-brain barrier. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive.

Astrocytes signal each other using calcium. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases.

There are generally two types of astrocytes, protoplasmic and fibrous, similar in function but distinct in morphology and distribution. Protoplasmic astrocytes have short, thick, highly branched processes and are typically found in gray matter. Fibrous astrocytes have long, thin, less branched processes and are more commonly found in white matter.

CNS Oligodendrocytes Oligodendrocytes are cells that coat axons in the central nervous system (CNS) with their cell membrane, called myelin, producing the so-called myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently.

CNS Ependymal cells Ependymal cells, also named ependymocytes, line the cavities of the CNS and make up the walls of the ventricles. These cells create and secrete cerebrospinal fluid(CSF) and beat their cilia to help circulate that CSF.

CNS Radial glia Radial glia cells arise from neuroepithelial cells after the onset of neurogenesis. Their differentiation abilities are more restricted than those of neuroepithelial cells. In the developing nervous system, radial glia function both as neuronal progenitors and as a scaffold upon which newborn neurons migrate. In the mature brain, the cerebellum and retina retain characteristic radial glial cells. In the cerebellum, these are Bergmann glia, which regulate synaptic plasticity. In the retina, the radial Müller cell is the principal glial cell, and participates in a bidirectional communication with neurons.

PNS Schwann cells Similar in function to oligodendrocytes, Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons.

PNS Satellite cells Satellite cells are small cells that line the exterior surface of PNS neurons and help regulate the external chemical environment.



[edit] Capacity to divide
Glia retain the ability to undergo cell division in adulthood, while most neurons cannot. The view is based on the general deficiency of the mature nervous system in replacing neurons after an insult or injury, such as a stroke or trauma, while very often there is a profound proliferation of glia, or gliosis near or at the site of damage. However, detailed studies found no evidence that 'mature' glia, such as astrocytes or oligodendrocytes, retain the ability of mitosis. Only the resident oligodendrocyte precursor cells seem to keep this ability after the nervous system matures. On the other hand, there are a few regions in the mature nervous system, such as the dentate gyrus of the hippocampus and the subventricular zone, where generation of new neurons can be observed.


[edit] Embryological development
Most glia are derived from ectodermal tissue of the developing embryo, particularly the neural tube and crest. The exception is microglia, which are derived from hemopoietic stem cells. In the adult, microglia are largely a self-renewing population and are distinct from macrophages and monocytes which infiltrate the injured and diseased CNS.

In the central nervous system, glia develop from the ventricular zone of the neural tube. These glia include the oligodendrocytes, ependymal cells, and astrocytes. In the peripheral nervous system, glia derive from the neural crest. These PNS glia include Schwann cells in nerves and satellite cells in ganglia.


[edit] History
Glia were discovered in 1856 by the pathologist Rudolf Virchow in his search for a 'connective tissue' in the brain.

The human brain contains about ten times more glial cells than neurons. [1] Following its discovery in the late 19th century, this fact underwent significant media distortion, emerging as the famous myth claiming that "we are using only 10% of our brain". The role of glial cells as managers of communications in the synapse gap, thus modifying learning pace, has been discovered only very recently (2004).


[edit] Additional images

Oligodendrocyte




Section of central canal of medulla spinalis, showing ependymal and neuroglial cells.




Transverse section of a cerebellar folium.









Meninges

Meninges of the CNS
Gray's subject #193 872
Artery middle meningeal artery, meningeal branches of the ascending pharyngeal artery, accessory meningeal artery, branch of anterior ethmoidal artery, meningeal branches of vertebral artery
Nerve middle meningeal nerve, nervus spinosus
MeSH Meninges
Dorlands/Elsevier m_09/12523818
The meninges (singular meninx) is the system of membranes which envelop the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.

Contents [hide]
1 Anatomy
1.1 Pia mater
1.2 Arachnoid mater
1.3 Dura mater
1.4 Spaces
2 Pathology
3 Additional images
4 References



[edit] Anatomy

[edit] Pia mater
The pia or pia mater is a very delicate membrane. It is attached to (nearest) the brain or the spinal cord. As such it follows all the minor contours of the brain (gyri and sulci). The pia mater is the meningeal envelope which firmly adheres to the surface of the brain and spinal cord. It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel to the brain and spinal cord, and its capillaries are responsible for nourishing the brain.


[edit] Arachnoid mater
The middle element of the meninges is the arachnoid mater, so named because of its spider web-like appearance. It provides a cushioning effect for the central nervous system. The arachnoid mater exists as a thin, transparent membrane. It is composed of fibrous tissue and, like the pia mater, is covered by flat cells also thought to be impermeable to fluid. The arachnoid does not follow the convolutions of the surface of the brain and so looks like a loosely fitting sac. In the region of the brain, particularly, a large number of fine filaments called arachnoid trabeculae pass from the arachnoid through the subarachnoid space to blend with the tissue of the pia mater.

The arachnoid and pia mater are sometimes together called the leptomeninges.


[edit] Dura mater
The dura mater (also rarely called meninx fibrosa, or pachymeninx) is a thick, durable membrane, closest to the skull. It contains larger blood vessels which split into the capilliaries in the pia mater. It is composed of dense fibrous tissue, and its inner surface is covered by flattened cells like those present on the surfaces of the pia mater and arachnoid. The dura mater is a sac which envelops the arachnoid and has been modified to serve several functions. The dura mater surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart.


[edit] Spaces
The subarachnoid space is the space which normally exists between the arachnoid and the pia mater, which is filled with cerebrospinal fluid.

Normally, the dura mater is attached to the skull in the head, or to the bones of the vertebral canal in the spinal cord. The arachnoid is attached to the dura mater, and the pia mater is attached to the central nervous system tissue. When the dura mater and the arachnoid separate through injury or illness, the space between them is the subdural space.


[edit] Pathology
There are three types of hemorrhage involving the meninges:[1]

A subarachnoid hemorrhage is acute bleeding under the arachnoid; it may occur spontaneously or as a result of trauma.
A subdural hematoma is a hematoma (collection of blood) located in a separation of the arachnoid from the dura mater. The small veins which connect the dura mater and the arachnoid are torn, usually during an accident, and blood can leak into this area.
An epidural hematoma similarly may arise after an accident or spontaneously.
Other medical conditions which affect the meninges include meningitis (usually from fungal, bacterial, or viral infection) and meningiomas arising from the meninges or from tumors formed elsewhere in the body which metastasize to the meninges.


[edit] Additional images

Diagrammatic representation of a section across the top of the skull




Diagrammatic section of scalp.









[edit] References
^ Orlando Regional Healthcare, Education and Development. 2004. "Overview of Adult Traumatic Brain Injuries." Retrieved on September 6, 2007.
[hide]v • d • eAnatomy: meninges of the brain and medulla spinalis
Layers Dura mater (Falx cerebri, Tentorium cerebelli, Falx cerebelli) • Arachnoid mater (Arachnoid granulation) • Subarachnoid space • Pia mater
Cisterns Cisterna magna • Pontine cistern • Interpeduncular cistern • Chiasmatic • Lateral cerebral fossa • Great cerebral vein
Other Cerebrospinal fluid



Nodes of Ranvier, also known as neurofibril nodes, are regularly spaced gaps in the myelin sheath around an axon or nerve fiber. About one micrometer in length, these gaps expose the axonal membrane to the extracellular fluid. (The myelin sheath is the fatty tissue layer coating the axon.)

Contents [hide]
1 Function in action potentials
2 History
3 See also
4 External links



[edit] Function in action potentials
The myelin sheath helps speed the neural impulse by insulating the electrical current and making it possible for the impulse to jump from node to node, a process known as saltatory conduction, as opposed to traveling down the axon in tiny increments.

An action potential is the sharp electrochemical response of a stimulated neuron, a neuron whose membrane potential has been changed by a nearby cell, cells, or an experimentor. In an action potential, the cell membrane potential changes drastically and quickly as ions flow in or out of the cell. The action potential "travels" from one place in the cell to another, but ion flow occurs only at the nodes of Ranvier. Therefore, the action potential signal "jumps" along the axon, from node to node, rather than propagating smoothly, as they do in axons that lack a myelin sheath. This is due to clustering of voltage-gated Na+ and K+ ion channels at the Nodes of Ranvier. Unmyelinated axons do not have Nodes of Ranvier; voltage gated ion channels in these axons are considerably less ordered and spread over the entire membrane surface.

Nodes of Ranvier can be thought of as a digital electronic amplifier held between insulated conductors - the myelinated axons (real electronic amplifiers function quite differently from this, but work in an analogous fashion, using a small electric potential to control a larger one).


[edit] History
The myelin sheath and the nodes were discovered by French pathologist and anatomist Louis-Antoine Ranvier (1835-1922).

oligodendrocytes (from Greek literally meaning few tree cells), or oligodendroglia (Greek, few tree glue),[1] are a variety of neuroglia. Their main function is the myelination of axons exclusively in the central nervous system of the higher vertebrates, a function performed by Schwann cells in the peripheral nervous system. A single oligodendrocyte can extend to up to 50 axons, wrapping around approximately 1 mm of each and forming the myelin sheath.
Contents
[hide]

* 1 Origin
* 2 Function
* 3 Pathology
* 4 Notes
* 5 References

[edit] Origin

Oligodendroglia arise during development from an oligodendrocyte precursor cell which can be identified by its expression of a number of antigens, including the ganglioside GD3 [2], the NG2 chondroitin sulfate proteoglycan [3], and the platelet derived growth factor-alpha receptor subunit PDGF-alphaR [4]. In the rat forebrain the majority of oligodendroglial progenitors arise during late embryogenesis and early postnatal development from cells of the subventricular zones (SVZ) of the lateral ventricles. SVZ cells migrate away from these germinal zones to populate both developing white and gray matter, where they differentiate and mature into myelin-forming oligodendroglia [5]. However, it is not clear whether all oligodendroglial progenitors undergo this sequence of events. It has been suggested that some undergo apoptosis [6] and that some fail to differentiate into oligodendroglia but persist into maturity as adult oligodendroglial progenitors [7].

[edit] Function

The nervous system of mammals depends crucially on the myelin sheath for insulation as it results in decreased ion leakage and lower capacitance of the cell membrane. There is also an overall increase in impulse speed as saltatory propagation of action potentials occurs at the nodes of Ranvier in between Schwann cells (of the PNS) and oligodendrocytes (of the CNS); furthermore miniaturization occurs, whereby impulse speed of myelinated axons increases linearly with the axon diameter, whereas the impulse speed of unmyelinated cells increases only with the square root of the diameter.

As part of the nervous system they are closely related to nerve cells and like all other glial cells the oligodendrocytes have a supporting role towards neurons. They are intimately involved in signal propagation, providing the same functionality as the insulation on a household electrical wire.

Satellite oligodendrocytes are functionally distinct from most oligodendrocytes. They are not attached to neurons and therefore do not serve an insulating role. They remain close to neurons and regulate the extracellular fluid.[8]

[edit] Pathology

Diseases that result in injury to the oligodendroglial cells include demyelinating diseases such as multiple sclerosis and leukodystrophies. Cerebral palsy (periventricular leukomalacia) is caused by damage to developing oligodendrocytes in the brain areas around the cerebral ventricles. Spinal cord injury also causes damage to oligodendrocytes. In cerebral palsy, spinal cord injury, stroke and possibly multiple sclerosis, oligodendrocytes are thought to be damaged by excessive release of the neurotransmitter glutamate. Oligodendrocyte dysfunction may also be implicated in the pathophysiology of schizophrenia and bipolar disorder [9]. Oligodendroglia are also susceptible to infection by the JC virus, which causes progressive multifocal leukoencephalopathy (PML), a condition which specifically affects white matter, typically in immunocompromised patients. Tumors of oligodendroglia are called oligodendrogliomas.

The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements through the action of skeletal muscles, and with reception of external stimuli, which helps keep the body in touch with its surroundings (e.g., touch, hearing, and sight).

The system includes all the neurons connected with muscles, skin and sense organs. The somatic nervous system consists of afferent nerves that receive sensory information from external sources and transmit them to the brain, and efferent nerves responsible for receiving brain communications for, say, muscle contraction.
Contents
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* 1 Nerve signal transmission
* 2 Vertebrate and invertebrate differences
* 3 Reflex arcs
* 4 See also

[edit] Nerve signal transmission

The somatic nervous system processes sensory information and controls all voluntary muscular systems within the body, with the exception of reflex arcs.

The basic route of nerve signals within the efferent somatic nervous system involves a sequence that begins in the upper cell bodies of motor neurons (upper motor neurons) within the precentral gyrus (which approximates the primary motor cortex). Stimuli from the precentral gyrus are transmitted from upper motor neurons and down the corticospinal tract, via axons to control skeletal (voluntary) muscles. These stimuli are conveyed from upper motor neurons through the ventral horn of the spinal cord, and across synapses to be received by the sensory receptors of alpha motor neuron (large lower motor neurons) of the brainstem and spinal cord.

Upper motor neurons release a neurotransmitter, acetylcholine, from their axon terminal knobs, which are received by nicotinic receptors of the alpha motor neurons. In turn, alpha motor neurons relay the stimuli received down their axons via the ventral root of the spinal cord. These signals then proceed to the neuromuscular junctions of skeletal muscles.

From there, acetylcholine is released from the axon terminal knobs of alpha motor neurons, and received by postsynaptic receptors (Nicotinic acetylcholine receptors) of muscles, thereby relaying the stimulus to contract muscle fibers.

[edit] Vertebrate and invertebrate differences

In invertebrates, depending on the neurotransmitter released and the type of receptor it binds, the response in the muscle fiber could either be excitatory or inhibitory. For vertebrates, however, the response of a muscle fiber to a neurotransmitter can only be excitatory, in other words, contractile.

[edit] Reflex arcs

A reflex arc is an automatic reaction that allows an organism to protect itself reflexively when an imminent danger is perceived. In response to certain stimuli, such as touching a hot surface, these reflexes are 'hard wired' through the spinal cord. A reflexive impulse travels up afferent nerves, through a spinal interneuron, and back down appropriate efferent nerves.
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visceral efferent nervous system
BC, 24 October 2007 (created 24 October 2007)

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The autonomic nervous system (ANS) (or visceral nervous system) is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These maintenance activities are primarily performed without conscious control or sensation. The ANS has far reaching effects, including: heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (the discharge of urine), and sexual arousal. Whereas most of its actions are involuntary, some ANS functions work in tandem with the conscious mind, such as breathing. Its main components are its sensory system, motor system (comprised of the parasympathetic nervous system and sympathetic nervous system), and the enteric nervous system.

The ANS is a classical term, widely used throughout the scientific and medical community. Its most useful definition could be: the sensory and motor neurons that innervate the viscera. These neurons form reflex arcs that pass through the lower brainstem or medulla oblongata. This explains that when the central nervous system (CNS) is damaged experimentally or by accident above that level, a vegetative life is still possible, whereby cardiovascular, digestive and respiratory functions are adequately regulated.
Contents
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* 1 Anatomy
o 1.1 Sensory neurons
o 1.2 Motor neurons
* 2 Function
o 2.1 Sympathetic nervous system
o 2.2 Parasympathetic nervous system
* 3 Neurotransmitters and pharmacology
* 4 See also
* 5 External links

[edit] Anatomy

The reflex arcs of the ANS comprise a sensory (or afferent) arm, and a motor (or efferent, or effector) arm. The latter alone is represented on the figure.

[edit] Sensory neurons

The sensory arm is made of “primary visceral sensory neurons” found in the peripheral nervous system (PNS), in “cranial sensory ganglia”: the geniculate, petrosal and nodose ganglia, appended respectively to cranial nerves VII, IX and X. These sensory neurons monitor the levels of carbon dioxide, oxygen and sugar in the blood, arterial pressure and the chemical composition of the stomach and gut content. (They also convey the sense of taste, a conscious perception). Blood oxygen and carbon dioxide are in fact directly sensed by the carotid body, a small collection of chemosensors at the bifurcation of the carotid artery, innervated by the petrosal (IXth) ganglion.

Primary sensory neurons project (synapse) onto “second order” or relay visceral sensory neurons located in the medulla oblongata, forming the nucleus of the solitary tract (nTS), that integrates all visceral information. The nTS also receives input from a nearby chemosensory center, the area postrema, that detects toxins in the blood and the cerebrospinal fluid and is essential for chemically induced vomiting and conditional taste aversion (the memory that ensures that an animal which has been poisoned by a food never touches it again). All these visceral sensory informations constantly and unconsciously modulate the activity of the motor neurons of the ANS

[edit] Motor neurons

Motor neurons of the ANS are also located in ganglia of the PNS, called “autonomic ganglia”. They belong to three categories with different effects on their target organs (see below “Function”): sympathetic, parasympathetic and enteric.

Sympathetic ganglia are located in two sympathetic chains close to the spinal cord: the prevertebral and pre-aortic chains. Parasympathetic ganglia, in contrast, are located in close proximity to the target organ: the submandibular ganglion close to salivatory glands, paracardiac ganglia close to the heart etc… Enteric ganglia, which as their name implies innervate the digestive tube, are located inside its walls and collectively contain as many neurons as the entire spinal cord, including local sensory neurons, motor neurons and interneurons. It is the only truly autonomous part of the ANS and the digestive tube can function surprisingly well even in isolation. For that reason the enteric nervous system has been called “the second brain”.

The activity of autonomic ganglionic neurons is modulated by “preganglionic neurons” (also called improperly but classically "visceral motoneurons") located in the central nervous system. Preganglionc sympathetic neurons are in the spinal cord, at thoraco-lumbar levels. Preganglionic parasympathetic neurons are in the medulla oblongata (forming visceral motor nuclei: the dorsal motor nucleus of the vagus nerve (dmnX), the nucleus ambiguus, and salivatory nuclei) and in the sacral spinal cord. Enteric neurons are also modulated by input from the CNS, from preganglionic neurons located, like parasympathetic ones, in the medulla oblongata (in the dmnX).

The feedback from the sensory to the motor arm of visceral reflex pathways is provided by direct or indirect connections between the nucleus of the solitary tract and visceral motoneurons.

[edit] Function

Sympathetic and parasympathetic divisions typically function in opposition to each other. But this opposition is better termed complementary in nature rather than antagonistic. For an analogy, one may think of the sympathetic division as the accelerator and the parasympathetic division as the brake. The sympathetic division typically functions in actions requiring quick responses. The parasympathetic division functions with actions that do not require immediate reaction. Consider sympathetic as "fight or flight" and parasympathetic as "rest and digest".

However, many instances of sympathetic and parasympathetic activity cannot be ascribed to "fight" or "rest" situations. For example, standing up from a reclining or sitting position would entail an unsustainable drop in blood pressure if not for a compensatory increase in the arterial sympathetic tonus. Another example is the constant, second to second modulation of heart rate by sympathetic and parasympathetic influences, as a function of the respiratory cycles. More generally, these two systems should be seen as permanently modulating vital functions, in usually antagonistic fashion, to achieve homeostasis. Some typical actions of the sympathetic and parasympathetic systems are listed below:

[edit] Sympathetic nervous system

* Diverts blood flow away from the gastro-intestinal (GI) tract and skin via vasoconstriction.
* Blood flow to skeletal muscles, the lung is not only maintained, but enhanced (by as much as 1200%, in the case of skeletal muscles).
* Dilates bronchioles of the lung, which allows for greater alveolar oxygen exchange.
* Increases heart rate and the contractility of cardiac cells (myocytes), thereby providing a mechanism for the enhanced blood flow to skeletal muscles.
* Dilates pupils and relaxes the lens, allowing more light to enter the eye.

[edit] Parasympathetic nervous system

* Dilates blood vessels leading to the GI tract, increasing blood flow. This is important following the consumption of food, due to the greater metabolic demands placed on the body by the gut.

* The parasympathetic nervous system can also constrict the bronchiolar diameter when the need for oxygen has diminished.

* During accommodation, the parasympathetic nervous system causes constriction of the pupil and lens.

* The parasympathetic nervous system stimulates salivary gland secretion, and accelerates peristalsis, so, in keeping with the rest and digest functions, appropriate PNS activity mediates digestion of food and indirectly, the absorption of nutrients.

* Is also involved in erection of genitals, via the pelvic splanchnic nerves 2–4.

[edit] Neurotransmitters and pharmacology

At the effector organs, sympathetic ganglionic neurons release noradrenaline (norepinephrine),along with other cotransmittors such as ATP, to act on adrenergic receptors, with the exception of the sweat glands and the adrenal medulla:

* acetycholine is the preganglionic neurotransmitter for both divisions of the ANS,as well as the postganglionic neurotransmitter of parasympathetic neurons.Nerves that releas