3.13:_Animal_Tissues

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<p class="lt-bio-3990">The development of a fertilized egg into a newborn child requires an average of 41 rounds of mitosis (<mjx-container class="MathJax CtxtMenu_Attached_0" jax="SVG" overflow="linebreak" tabindex="0" ctxtmenu_counter="96" style="font-size: 85%; position: relative;"><svg width="2.919ex" height="2.47ex" role="img" focusable="false" viewbox="0 -841.7 1290.1 1091.7" aria-hidden="true" style="vertical-align: -0.566ex;"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math" data-latex="2^{41} = 2.2 \times 10^{12}" data-semantic-type="relseq" data-semantic-role="equality" data-semantic-annotation="depth:1" data-semantic-id="10" data-semantic-children="2,9" data-semantic-content="3" data-semantic-attributes="latex:2^{41} = 2.2 \times 10^{12}" data-semantic-owns="2 3 9" data-semantic-level-number="0" data-speech-node="true" data-semantic-structure="(10 (2 0 1) 3 (9 4 5 (8 6 7)))"><g data-mml-node="msup" 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data-semantic-attributes="latex:2^{41} = 2.2 \times 10^{12}" data-semantic-owns="2 3 9" data-semantic-level-number="0" data-speech-node="true" data-semantic-structure="(10 (2 0 1) 3 (9 4 5 (8 6 7)))"><g data-mml-node="mo" data-latex="=" data-semantic-type="relation" data-semantic-role="equality" data-semantic-annotation="nemeth:number;depth:2" data-semantic-id="3" data-semantic-parent="10" data-semantic-attributes="latex:=" data-semantic-operator="relseq,=" data-semantic-level-number="1" data-speech-node="true"><use data-c="3D" href="#MJX-97-NCM-N-3D"></use></g><g data-mml-node="mrow" data-semantic-added="true" data-semantic-type="infixop" data-semantic-role="multiplication" data-semantic-annotation="depth:2" data-semantic-id="9" data-semantic-children="4,8" data-semantic-content="5" data-semantic-parent="10" data-semantic-owns="4 5 8" data-semantic-level-number="1" data-speech-node="true" transform="translate(1055.8,0)"><g data-mml-node="mn" data-latex="2.2" data-semantic-type="number" data-semantic-role="float" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:3" data-semantic-id="4" data-semantic-parent="9" data-semantic-attributes="latex:2.2" data-semantic-level-number="2" data-speech-node="true"><use data-c="32" href="#MJX-97-NCM-N-32"></use><use data-c="2E" href="#MJX-97-NCM-N-2E" transform="translate(500,0)"></use><use data-c="32" href="#MJX-97-NCM-N-32" transform="translate(778,0)"></use></g></g></g></g></svg><mjx-break size="3"> </mjx-break><svg width="6.313ex" height="2.52ex" role="img" focusable="false" viewbox="0 -864 2790.3 1114" style="vertical-align: -0.566ex;"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math" data-latex="2^{41} = 2.2 \times 10^{12}" data-semantic-type="relseq" data-semantic-role="equality" data-semantic-annotation="depth:1" data-semantic-id="10" data-semantic-children="2,9" data-semantic-content="3" data-semantic-attributes="latex:2^{41} = 2.2 \times 10^{12}" data-semantic-owns="2 3 9" data-semantic-level-number="0" data-speech-node="true" data-semantic-structure="(10 (2 0 1) 3 (9 4 5 (8 6 7)))"><g data-mml-node="mrow" data-semantic-added="true" data-semantic-type="infixop" data-semantic-role="multiplication" data-semantic-annotation="depth:2" data-semantic-id="9" data-semantic-children="4,8" data-semantic-content="5" data-semantic-parent="10" data-semantic-owns="4 5 8" data-semantic-level-number="1" data-speech-node="true"><g data-mml-node="mo" data-latex="\times" data-semantic-type="operator" data-semantic-role="multiplication" data-semantic-annotation="depth:3" data-semantic-id="5" data-semantic-parent="9" data-semantic-attributes="latex:\times" data-semantic-operator="infixop,&times;" data-semantic-level-number="2" data-speech-node="true"><use data-c="D7" href="#MJX-97-NCM-N-D7"></use></g><g data-mml-node="msup" data-latex="10^{12}" data-semantic-type="superscript" 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During this period, the cells produced by mitosis enter different pathways of differentiation; some becoming blood cells, some muscle cells, and so on. There are more than 100 visibly-distinguishable kinds of differentiated cells in the vertebrate animal. These are organized into tissues; the tissues into organs. Groups of organs make up the various systems &mdash; digestive, excretory, etc. &mdash; of the body (Figure <mjx-container class="MathJax CtxtMenu_Attached_0" jax="SVG" overflow="linebreak" tabindex="0" ctxtmenu_counter="97" style="font-size: 85%; position: relative;"><svg width="5.783ex" height="1.557ex" role="img" focusable="false" viewbox="0 -666 2556 688" aria-hidden="true" style="vertical-align: -0.05ex;"><defs><path id="MJX-98-NCM-N-33" d="M303 353C369 378 431 441 431 526C431 569 410 604 369 631C333 654 292 666 246 666C201 666 162 654 127 631C88 605 68 571 68 528C68 495 90 472 122 472C154 472 176 495 176 527C176 560 157 578 119 580C145 615 186 633 242 633C302 633 332 598 332 527C332 485 324 450 309 421C282 373 245 364 183 364C171 362 165 357 165 348C165 333 172 333 192 333L235 333C310 333 348 280 348 173C348 88 317 14 241 14C176 14 128 36 99 80C134 79 160 105 160 139C160 173 135 198 101 198C62 198 42 178 42 137C42 88 64 49 108 18C147-9 193-22 244-22C301-22 350-3 393 34C436 71 457 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transform="translate(500,0)"><g data-mml-node="mo" data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-id="1" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true"><use data-c="2E" href="#MJX-99-NCM-N-2E"></use></g></g><g data-mml-node="mn" data-latex="13" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-id="2" data-semantic-parent="5" data-semantic-attributes="latex:13" data-semantic-level-number="1" data-speech-node="true" transform="translate(778,0)"><use data-c="31" href="#MJX-99-NCM-N-31"></use><use data-c="33" href="#MJX-99-NCM-N-33" transform="translate(500,0)"></use></g><g data-mml-node="TeXAtom" data-mjx-texclass="ORD" data-latex="{.}" transform="translate(1778,0)"><g data-mml-node="mo" data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-id="3" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true"><use data-c="2E" href="#MJX-99-NCM-N-2E"></use></g></g><g data-mml-node="mn" data-latex="1" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-id="4" data-semantic-parent="5" data-semantic-attributes="latex:1" data-semantic-level-number="1" data-speech-node="true" transform="translate(2056,0)"><use data-c="31" href="#MJX-99-NCM-N-31"></use></g></g></g></g></svg><mjx-assistive-mml unselectable="on" display="inline"><math data-latex="\PageIndex{1}" data-semantic-structure="(5 0 1 2 3 4)"><mrow data-mjx-texclass="ORD" data-latex="1}" data-semantic-type="punctuated" data-semantic-role="sequence" data-semantic-annotation="depth:1" data-semantic-="" data-semantic-children="0,1,2,3,4" data-semantic-content="1,3" data-semantic-attributes="latex:\PageIndex{1};texclass:ORD" data-semantic-owns="0 1 2 3 4" data-semantic-level-number="0" data-speech-node="true"><mn data-latex="3" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:3" data-semantic-level-number="1" data-speech-node="true">3</mn><mrow data-mjx-texclass="ORD" data-latex="{.}"><mo data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true">.</mo></mrow><mn data-latex="13" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:13" data-semantic-level-number="1" data-speech-node="true">13</mn><mrow data-mjx-texclass="ORD" data-latex="{.}"><mo data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true">.</mo></mrow><mn data-latex="1" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:1" data-semantic-level-number="1" data-speech-node="true">1</mn></mrow></math></mjx-assistive-mml></mjx-container>).</p>

<figure><img style="width: 571px; height: 375px;" class="internal" alt="Diagram showing a cross-section of an arm with close-ups of different tissues: epithelial, dense irregular connective, skeletal muscle, hyaline cartilage, adipose, blood, and nerve tissue." loading="lazy" width="571px" height="375px" src="https://bio.libretexts.org/@api/deki/files/5953/Picture_1.jpg?revision=1&amp;size=bestfit&amp;width=571&amp;height=375" />
<figcaption>Figure <mjx-container class="MathJax CtxtMenu_Attached_0" jax="SVG" overflow="linebreak" tabindex="0" ctxtmenu_counter="99" style="font-size: 85%; position: relative;"><svg width="5.783ex" height="1.557ex" role="img" focusable="false" viewbox="0 -666 2556 688" aria-hidden="true" style="vertical-align: -0.05ex;"><defs><path id="MJX-100-NCM-N-33" d="M303 353C369 378 431 441 431 526C431 569 410 604 369 631C333 654 292 666 246 666C201 666 162 654 127 631C88 605 68 571 68 528C68 495 90 472 122 472C154 472 176 495 176 527C176 560 157 578 119 580C145 615 186 633 242 633C302 633 332 598 332 527C332 485 324 450 309 421C282 373 245 364 183 364C171 362 165 357 165 348C165 333 172 333 192 333L235 333C310 333 348 280 348 173C348 88 317 14 241 14C176 14 128 36 99 80C134 79 160 105 160 139C160 173 135 198 101 198C62 198 42 178 42 137C42 88 64 49 108 18C147-9 193-22 244-22C301-22 350-3 393 34C436 71 457 117 457 173C457 267 383 332 303 353Z"></path><path id="MJX-100-NCM-N-2E" d="M192 53C192 82 168 106 139 106C110 106 86 82 86 53C86 24 110 0 139 0C168 0 192 24 192 53Z"></path><path id="MJX-100-NCM-N-31" d="M269 666C228 624 168 603 89 603L89 564C141 564 184 572 217 588L217 82C217 64 213 52 204 47C195 42 170 39 130 39L95 39L95 0C120 2 174 3 257 3C340 3 394 2 419 0L419 39L384 39C343 39 318 42 310 47C302 52 297 64 297 82L297 636C297 660 295 666 269 666Z"></path></defs><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math" data-latex="\PageIndex{1}" data-semantic-structure="(5 0 1 2 3 4)"><g data-mml-node="TeXAtom" data-mjx-texclass="ORD" data-latex="1}" data-semantic-type="punctuated" data-semantic-role="sequence" data-semantic-annotation="depth:1" data-semantic-id="5" data-semantic-children="0,1,2,3,4" data-semantic-content="1,3" data-semantic-attributes="latex:\PageIndex{1};texclass:ORD" data-semantic-owns="0 1 2 3 4" data-semantic-level-number="0" data-speech-node="true"><g data-mml-node="mn" data-latex="3" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-id="0" data-semantic-parent="5" data-semantic-attributes="latex:3" data-semantic-level-number="1" data-speech-node="true"><use data-c="33" href="#MJX-100-NCM-N-33"></use></g><g data-mml-node="TeXAtom" data-mjx-texclass="ORD" data-latex="{.}" transform="translate(500,0)"><g data-mml-node="mo" data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-id="1" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true"><use data-c="2E" href="#MJX-100-NCM-N-2E"></use></g></g><g data-mml-node="mn" data-latex="13" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-id="2" data-semantic-parent="5" data-semantic-attributes="latex:13" data-semantic-level-number="1" data-speech-node="true" transform="translate(778,0)"><use data-c="31" href="#MJX-100-NCM-N-31"></use><use data-c="33" href="#MJX-100-NCM-N-33" transform="translate(500,0)"></use></g><g data-mml-node="TeXAtom" data-mjx-texclass="ORD" data-latex="{.}" transform="translate(1778,0)"><g data-mml-node="mo" data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-id="3" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true"><use data-c="2E" href="#MJX-100-NCM-N-2E"></use></g></g><g data-mml-node="mn" data-latex="1" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-id="4" data-semantic-parent="5" data-semantic-attributes="latex:1" data-semantic-level-number="1" data-speech-node="true" transform="translate(2056,0)"><use data-c="31" href="#MJX-100-NCM-N-31"></use></g></g></g></g></svg><mjx-assistive-mml unselectable="on" display="inline"><math data-latex="\PageIndex{1}" data-semantic-structure="(5 0 1 2 3 4)"><mrow data-mjx-texclass="ORD" data-latex="1}" data-semantic-type="punctuated" data-semantic-role="sequence" data-semantic-annotation="depth:1" data-semantic-="" data-semantic-children="0,1,2,3,4" data-semantic-content="1,3" data-semantic-attributes="latex:\PageIndex{1};texclass:ORD" data-semantic-owns="0 1 2 3 4" data-semantic-level-number="0" data-speech-node="true"><mn data-latex="3" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:3" data-semantic-level-number="1" data-speech-node="true">3</mn><mrow data-mjx-texclass="ORD" data-latex="{.}"><mo data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true">.</mo></mrow><mn data-latex="13" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:13" data-semantic-level-number="1" data-speech-node="true">13</mn><mrow data-mjx-texclass="ORD" data-latex="{.}"><mo data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true">.</mo></mrow><mn data-latex="1" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:1" data-semantic-level-number="1" data-speech-node="true">1</mn></mrow></math></mjx-assistive-mml></mjx-container>: Animal Tissues</figcaption>
</figure>

<p class="lt-bio-3990">The actual number of differentiated cell types is surely much larger than 100. All lymphocytes, for example, look alike but actually represent a variety of different functional types, e.g., B cells, T cells of various subsets. The neurons of the central nervous system must exist in a thousand or more different functional types, each representing the result of a particular pathway of differentiation. This page will give a brief introduction to the major types of animal tissues.</p>

<table class="mt-responsive-table" align="center" cellpadding="0" cellspacing="0">
    <caption>Table <mjx-container class="MathJax CtxtMenu_Attached_0" jax="SVG" overflow="linebreak" tabindex="0" ctxtmenu_counter="100" style="font-size: 85%; position: relative;"><svg width="5.783ex" height="1.557ex" role="img" focusable="false" viewbox="0 -666 2556 688" aria-hidden="true" style="vertical-align: -0.05ex;"><defs><path id="MJX-101-NCM-N-33" d="M303 353C369 378 431 441 431 526C431 569 410 604 369 631C333 654 292 666 246 666C201 666 162 654 127 631C88 605 68 571 68 528C68 495 90 472 122 472C154 472 176 495 176 527C176 560 157 578 119 580C145 615 186 633 242 633C302 633 332 598 332 527C332 485 324 450 309 421C282 373 245 364 183 364C171 362 165 357 165 348C165 333 172 333 192 333L235 333C310 333 348 280 348 173C348 88 317 14 241 14C176 14 128 36 99 80C134 79 160 105 160 139C160 173 135 198 101 198C62 198 42 178 42 137C42 88 64 49 108 18C147-9 193-22 244-22C301-22 350-3 393 34C436 71 457 117 457 173C457 267 383 332 303 353Z"></path><path id="MJX-101-NCM-N-2E" d="M192 53C192 82 168 106 139 106C110 106 86 82 86 53C86 24 110 0 139 0C168 0 192 24 192 53Z"></path><path id="MJX-101-NCM-N-31" d="M269 666C228 624 168 603 89 603L89 564C141 564 184 572 217 588L217 82C217 64 213 52 204 47C195 42 170 39 130 39L95 39L95 0C120 2 174 3 257 3C340 3 394 2 419 0L419 39L384 39C343 39 318 42 310 47C302 52 297 64 297 82L297 636C297 660 295 666 269 666Z"></path></defs><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math" data-latex="\PageIndex{1}" data-semantic-structure="(5 0 1 2 3 4)"><g data-mml-node="TeXAtom" data-mjx-texclass="ORD" data-latex="1}" data-semantic-type="punctuated" data-semantic-role="sequence" data-semantic-annotation="depth:1" data-semantic-id="5" data-semantic-children="0,1,2,3,4" data-semantic-content="1,3" data-semantic-attributes="latex:\PageIndex{1};texclass:ORD" data-semantic-owns="0 1 2 3 4" data-semantic-level-number="0" data-speech-node="true"><g data-mml-node="mn" data-latex="3" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-id="0" data-semantic-parent="5" data-semantic-attributes="latex:3" data-semantic-level-number="1" data-speech-node="true"><use data-c="33" href="#MJX-101-NCM-N-33"></use></g><g data-mml-node="TeXAtom" data-mjx-texclass="ORD" data-latex="{.}" transform="translate(500,0)"><g data-mml-node="mo" data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-id="1" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true"><use data-c="2E" href="#MJX-101-NCM-N-2E"></use></g></g><g data-mml-node="mn" data-latex="13" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-id="2" data-semantic-parent="5" data-semantic-attributes="latex:13" data-semantic-level-number="1" data-speech-node="true" transform="translate(778,0)"><use data-c="31" href="#MJX-101-NCM-N-31"></use><use data-c="33" href="#MJX-101-NCM-N-33" transform="translate(500,0)"></use></g><g data-mml-node="TeXAtom" data-mjx-texclass="ORD" data-latex="{.}" transform="translate(1778,0)"><g data-mml-node="mo" data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-id="3" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true"><use data-c="2E" href="#MJX-101-NCM-N-2E"></use></g></g><g data-mml-node="mn" data-latex="1" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-id="4" data-semantic-parent="5" data-semantic-attributes="latex:1" data-semantic-level-number="1" data-speech-node="true" transform="translate(2056,0)"><use data-c="31" href="#MJX-101-NCM-N-31"></use></g></g></g></g></svg><mjx-assistive-mml unselectable="on" display="inline"><math data-latex="\PageIndex{1}" data-semantic-structure="(5 0 1 2 3 4)"><mrow data-mjx-texclass="ORD" data-latex="1}" data-semantic-type="punctuated" data-semantic-role="sequence" data-semantic-annotation="depth:1" data-semantic-="" data-semantic-children="0,1,2,3,4" data-semantic-content="1,3" data-semantic-attributes="latex:\PageIndex{1};texclass:ORD" data-semantic-owns="0 1 2 3 4" data-semantic-level-number="0" data-speech-node="true"><mn data-latex="3" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:3" data-semantic-level-number="1" data-speech-node="true">3</mn><mrow data-mjx-texclass="ORD" data-latex="{.}"><mo data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true">.</mo></mrow><mn data-latex="13" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:13" data-semantic-level-number="1" data-speech-node="true">13</mn><mrow data-mjx-texclass="ORD" data-latex="{.}"><mo data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true">.</mo></mrow><mn data-latex="1" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:1" data-semantic-level-number="1" data-speech-node="true">1</mn></mrow></math></mjx-assistive-mml></mjx-container>: Classification of Animal Tissues</caption>
    <tbody>
        <tr>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="4" style="text-align:center;vertical-align:middle;"><strong>Epithelial Tissues </strong></td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;vertical-align:middle;">Linings and Coverings</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Simple Epithelia</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;vertical-align:middle;">Classifying or Naming Epithelia</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Stratified Epithelia</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="2" style="text-align:center;vertical-align:middle;">Glands</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Exocrine Glands</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Endocrine Glands</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="7" style="text-align:center;vertical-align:middle;"><strong>Connective Tissues </strong></td>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="2" style="text-align:center;vertical-align:middle;">Fluid Connective Tissues</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Lymph</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Blood</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="3" style="text-align:center;vertical-align:middle;">Connective Tissues Proper</td>
            <td class="mt-noheading  lt-bio-3990">Loose Connective Tissues</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Loose Connective Tissues and Inflammation</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Dense Connective Tissues</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="2" style="text-align:center;vertical-align:middle;">Supportive Connective Tissues</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Osseous Tissue</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Cartilage</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="3" style="text-align:center;vertical-align:middle;"><strong>Muscle Tissues </strong></td>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="1" style="text-align:center;vertical-align:middle;">Non-striated</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Smooth muscle</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="2" style="text-align:center;vertical-align:middle;">Striated</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Skeletal Muscle</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Cardiac Muscle</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" colspan="1" rowspan="3" style="text-align:center;vertical-align:middle;"><strong>Nervous Tissues </strong></td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;vertical-align:middle;">Neurons</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Multipolar Neurons in CNS</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;vertical-align:middle;">Nerves</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Nerves of the PNS</td>
        </tr>
        <tr>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;vertical-align:middle;">Receptors</td>
            <td class="mt-noheading  lt-bio-3990" style="text-align:center;">Miessner's and Pacinian Corpuscles</td>
        </tr>
    </tbody>
</table>

<span id="Epithelial"></span><span id="Epithelial"></span><h2 class="lt-bio-3990">Epithelial</h2>

<p class="lt-bio-3990">Epithelial tissue is made of closely-packed cells arranged in flat sheets. Epithelia form the surface of the skin, line the various cavities and tubes of the body, and cover the internal organs. Epithelia that form the interface between the internal and external environments. Skin as well as the lining of the mouth and nasal cavity. These are derived from <strong>ectoderm</strong>. Inner lining of the GI tract, lungs, urinary bladder, exocrine glands, vagina and more. These are derived from <strong>endoderm</strong>.</p>

<p class="lt-bio-3990">The <strong>apical surface</strong> of these epithelial cells is exposed to the &quot;external environment&quot;, the lumen of the organ or the air.</p>

<ul>
    <li class="lt-bio-3990"><strong>Mesothelia</strong>. These are derived from mesoderm.

<ul>
        <li class="lt-bio-3990">pleura &mdash; the outer covering of the lungs and the inner lining of the thoracic (chest) cavity.</li>
        <li class="lt-bio-3990">peritoneum &mdash; the outer covering of all the abdominal organs and the inner lining of the abdominal cavity.</li>
        <li class="lt-bio-3990">pericardium &mdash; the outer lining of the heart.</li>
    </ul>
    </li>
    <li class="lt-bio-3990"><strong>Endothelia</strong>. These are derived from mesoderm. The inner lining of the heart, all blood and lymphatic vessels.</li>
</ul>

<p class="lt-bio-3990">The <strong>basolateral surface</strong> of all epithelia is exposed to the internal environment - extracellular fluid (ECF). The entire sheet of epithelial cells is attached to a layer of extracellular matrix that is called the basement membrane or, better (because it is not a membrane in the biological sense), the <strong>basal lamina</strong>.</p>

<p class="lt-bio-3990">The function of epithelia always reflects the fact that they are boundaries between masses of cells and a cavity or space. Some examples include:</p>

<ul>
    <li class="lt-bio-3990">The epithelium of the skin protects the underlying tissues from mechanical damage, ultraviolet light, dehydration and invasion by bacteria</li>
    <li class="lt-bio-3990">The columnar epithelium of the intestine secretes digestive enzymes into the intestine and absorbs the products of digestion from it.</li>
    <li class="lt-bio-3990">An epithelium also lines our air passages and the alveoli of the lungs. It secretes mucus which keeps it from drying out and traps inhaled dust particles. Most of its cells have cilia on their apical surface that propel the mucus with its load of foreign matter back up to the throat.</li>
</ul>

<span id="Muscle"></span><span id="Muscle"></span><h2 class="lt-bio-3990">Muscle</h2>

<p class="lt-bio-3990">Three kinds of muscle are found in vertebrates. <strong>Skeletal muscle</strong> is made of long fibers whose contraction provides the force of locomotion and other <strong>voluntary</strong> body movements. <strong>Smooth muscle</strong> lines the walls of the hollow structures of the body, such as the intestine, urinary bladder, uterus, and blood vessels. Its contraction, which is <strong>involuntary</strong>, reduces the size of these hollow organs. The heart is made of <strong>cardiac muscle</strong>.</p>

<span id="Connective"></span><span id="Connective"></span><h2 class="lt-bio-3990">Connective</h2>

<p class="lt-bio-3990">The cells of connective tissue are embedded in a great amount of extracellular material. This <strong>matrix</strong> is secreted by the cells. It consists of protein fibers embedded in an amorphous mixture of protein-polysaccharide (&quot;proteoglycan&quot;) molecules. Supporting connective tissue gives strength, support, and protection to the soft parts of the body.</p>

<ul>
    <li class="lt-bio-3990"><strong>cartilage</strong>. Example: the outer ear</li>
    <li class="lt-bio-3990"><strong>bone</strong>. The matrix of bone contains collagen fibers and mineral deposits. The most abundant mineral is calcium phosphate, although magnesium, carbonate, and fluoride ions are also present.</li>
</ul>

<p class="lt-bio-3990">Dense connective tissue is often called fibrous connective tissue and include <strong>Tendons</strong> and <strong>Ligaments</strong>. Tendons connect muscle to bone with a The matrix is principally Type I collagen, and the fibers are all oriented parallel to each other. Tendons are strong but not elastic. <strong>Ligaments</strong> attach one bone to another and contain both collagen and also the protein <strong>elastin</strong>. Elastin permits ligaments to be stretched.</p>

<p class="lt-bio-3990">Loose connective tissue is distributed throughout the body. It serves as a packing and binding material for most of our organs. Sheets of loose connective tissue that bind muscles and other structures together are called <strong>fascia</strong>. Collagen, elastin, and other proteins are found in the matrix of loose connective tissue. Both dense and loose connective tissue are derived from cells called <strong>fibroblasts</strong>, which secrete the extracellular matrix.</p>

<span id="Adipose_Tissue"></span><span id="Adipose_Tissue"></span><h2 class="lt-bio-3990">Adipose Tissue</h2>

<p class="lt-bio-3990">Adipose tissue is &quot;fat&quot;. There are two kinds found in mammals: <strong>white adipose tissue</strong> (WAT) and <strong>brown adipose tissue</strong> (BAT). The WAT in which the cells, called <strong>adipocytes</strong>, have become almost filled with oil, which is confined within a single membrane-enclosed droplet. Virtually all of the &quot;fat&quot; in adult humans is white adipose tissue. BAT in which the adipocytes contain many small droplets of oil as well as many mitochondria. White adipose tissue and brown adipose tissue differ in function as well as cellular structure. These differences are described elsehwhere.</p>

<p class="lt-bio-3990">New adipocytes in white adipose tissue are formed throughout life from a pool of precursor cells. These are needed to replace those that die (after an average life span of 10 years). Whether the total <strong>number</strong> of these adipocytes increases in humans becoming fatter as adults is still uncertain. If not, why do so many of us get fatter as we age? Because of the increased <strong>size</strong> of individual adipocytes as they become filled with oil. The adipocytes of white adipose tissue secrete several hormones, including leptin and adiponectin.</p>

<span id="Nerve"></span><span id="Nerve"></span><h2 class="lt-bio-3990">Nerve</h2>

<p class="lt-bio-3990">Nerve tissue is composed of nerve cells called neurons and glial cells. Neurons are specialized for the conduction of nerve impulses; a typical neuron consists of a <strong>cell body</strong> which contains the nucleus; a number of short fibers &mdash; <strong>dendrites</strong> &mdash; extending from the cell body and a single long fiber, the <strong>axon</strong>. The nerve impulse is conducted along the axon. The tips of axons meet other neurons at junctions called <strong>synapses, muscles (called neuromuscular junctions) and </strong>glands.</p>

<p class="lt-bio-3990">Glial cells surround neurons. Once thought to be simply support for neurons (<em>glia</em> = glue), they turn out to serve several important functions. There are three types:</p>

<ul>
    <li class="lt-bio-3990"><strong>Schwann cells</strong>. These produce the myelin sheath that surrounds many axons in the peripheral nervous system.</li>
    <li class="lt-bio-3990"><strong>Oligodendrocytes</strong>. These produce the myelin sheath that surrounds many axons in the central nervous system (brain and spinal cord).</li>
    <li class="lt-bio-3990"><strong>Astrocytes</strong>. These, often star-shaped cells are clustered around synapses and the nodes of Ranvier where they perform a variety of functions such as:
    <ul>
        <li class="lt-bio-3990">modulating the activity of neurons</li>
        <li class="lt-bio-3990">supplying neurons with materials (e.g. glucose and lactate) as well as some signaling molecules</li>
        <li class="lt-bio-3990">regulating the flow of blood to their region of the brain. It is primarily the metabolic activity of astrocytes that is being measured in brain imaging by positron-emission tomography (PET) and functional magnetic resonance imaging (fMRI).</li>
        <li class="lt-bio-3990">pruning away (by phagocytosis) weak synapses</li>
    </ul>
    </li>
</ul>

<p class="lt-bio-3990">In addition, the central nervous system contains many <strong>microglia</strong> &mdash; mobile cells (macrophages) that respond to damage (e.g., from an infection) by engulfing cell debris and secreting inflammatory cytokines like tumor necrosis factor (TNF-&alpha;) and interleukin-1 (IL-1). Microglia are also active in the healthy brain, at least in young mice where, like astrocytes, they engulf synapses thus reducing the number of synapses in the developing brain.</p>

<span id="Blood"></span><span id="Blood"></span><h2 class="lt-bio-3990">Blood</h2>

<p class="lt-bio-3990">The <strong>bone marrow</strong> is the source of all the cells of the blood. These include <strong>red blood cells</strong> (RBCs or <strong>erythrocytes</strong>), five kinds of <strong>white blood cells</strong> (WBCs or <strong>leukocytes</strong>), and <strong>platelets</strong> (or <strong>thrombocytes</strong>).</p>

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<hr class="autoattribution-divider" /><div class="autoattribution"><p>This page titled <a target="_blank" class="internal mt-self-link" href="/Sandboxes/johnnyphung/biology/03:_The_Cellular_Basis_of_Life/3.13:_Animal_Tissues">3.13: Animal Tissues</a> is shared under a <a rel="nofollow" href="https://creativecommons.org/licenses/by/3.0" target="_blank">CC BY  3.0</a>  license and was authored, remixed, and/or curated by <a rel="nofollow" target="_blank" href="http://www.biology-pages.info/">John W. Kimball</a> via <a rel="nofollow" href="https://www.biology-pages.info/" target="_blank">source content</a> that was edited to the style and standards of the LibreTexts platform.</p></div>

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