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<span>Function</span> </div> </a> <button aria-controls="toc-Function-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Function subsection</span> </button> <ul id="toc-Function-sublist" class="vector-toc-list"> <li id="toc-Thermal_insulation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Thermal_insulation"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Thermal insulation</span> </div> </a> <ul id="toc-Thermal_insulation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Self_defence" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Self_defence"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Self defence</span> </div> </a> <ul id="toc-Self_defence-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Sebum_excretion" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Sebum_excretion"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Sebum excretion</span> </div> </a> <ul id="toc-Sebum_excretion-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Hair_follicle_stability" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Hair_follicle_stability"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4</span> <span>Hair follicle stability</span> </div> </a> <ul id="toc-Hair_follicle_stability-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Clinical_significance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Clinical_significance"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.5</span> <span>Clinical significance</span> </div> </a> <ul id="toc-Clinical_significance-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li 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Available in 15 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-15" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">15 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%B9%D8%B6%D9%84%D8%A9_%D9%85%D9%82%D9%81%D8%A9_%D9%84%D9%84%D8%B4%D8%B9%D8%B1%D8%A9" title="عضلة مقفة للشعرة – Arabic" lang="ar" hreflang="ar" data-title="عضلة مقفة للشعرة" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Vzp%C5%99imova%C4%8D_chlupu" title="Vzpřimovač chlupu – Czech" lang="cs" hreflang="cs" data-title="Vzpřimovač chlupu" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Musculus_arrector_pili" title="Musculus arrector pili – German" lang="de" hreflang="de" data-title="Musculus arrector pili" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Karvap%C3%BCstitaja" title="Karvapüstitaja – Estonian" lang="et" hreflang="et" data-title="Karvapüstitaja" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/M%C3%BAsculo_erector_del_pelo" title="Músculo erector del pelo – Spanish" lang="es" hreflang="es" data-title="Músculo erector del pelo" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%85%D8%A7%D9%87%DB%8C%DA%86%D9%87_%D8%B1%D8%A7%D8%B3%D8%AA%E2%80%8C%DA%A9%D9%86%D9%86%D8%AF%D9%87_%D9%85%D9%88" title="ماهیچه راست‌کننده مو – Persian" lang="fa" hreflang="fa" data-title="ماهیچه راست‌کننده مو" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Muscle_%C3%A9recteur_du_poil" title="Muscle érecteur du poil – French" lang="fr" hreflang="fr" data-title="Muscle érecteur du poil" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Muscolo_erettore_del_pelo" title="Muscolo erettore del pelo – Italian" lang="it" hreflang="it" data-title="Muscolo erettore del pelo" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Musculus_arrector_pili" title="Musculus arrector pili – Dutch" lang="nl" hreflang="nl" data-title="Musculus arrector pili" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E7%AB%8B%E6%AF%9B%E7%AD%8B" title="立毛筋 – Japanese" lang="ja" hreflang="ja" data-title="立毛筋" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Mi%C4%99sie%C5%84_przyw%C5%82osowy" title="Mięsień przywłosowy – Polish" lang="pl" hreflang="pl" data-title="Mięsień przywłosowy" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/M%C3%BAsculo_eretor_do_pelo" title="Músculo eretor do pelo – Portuguese" lang="pt" hreflang="pt" data-title="Músculo eretor do pelo" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Arrector_pili" title="Arrector pili – Simple English" lang="en-simple" hreflang="en-simple" data-title="Arrector pili" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Karvankohottajalihas" title="Karvankohottajalihas – Finnish" lang="fi" hreflang="fi" data-title="Karvankohottajalihas" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E7%AB%8B%E6%AF%9B%E8%82%8C" title="立毛肌 – Chinese" lang="zh" hreflang="zh" data-title="立毛肌" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> 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class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Muscles attached to hair follicles</div> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox"><tbody><tr><th colspan="2" class="infobox-header" style="background-color: #efefef">Details</th></tr><tr><th scope="row" class="infobox-label" style="padding-right:0.25em"><a href="/wiki/Nerve" title="Nerve">Nerve</a></th><td class="infobox-data"><a href="/wiki/Sympathetic_nervous_system" title="Sympathetic nervous system">Sympathetic</a> <a href="/wiki/Postganglionic_nerve_fibers" title="Postganglionic nerve fibers">postganglionic nerve fibers</a></td></tr><tr><th colspan="2" class="infobox-header" style="background-color: #efefef">Identifiers</th></tr><tr><th scope="row" class="infobox-label" style="padding-right:0.25em"><a href="/wiki/Terminologia_Anatomica" title="Terminologia Anatomica">TA98</a></th><td class="infobox-data"><a rel="nofollow" class="external text" href="https://ifaa.unifr.ch/Public/EntryPage/TA98%20Tree/Entity%20TA98%20EN/16.0.00.024%20Entity%20TA98%20EN.htm">A16.0.00.024</a></td></tr><tr><th scope="row" class="infobox-label" style="padding-right:0.25em"><a href="/wiki/Terminologia_Anatomica" title="Terminologia Anatomica">TA2</a></th><td class="infobox-data"><a rel="nofollow" class="external text" href="https://ta2viewer.openanatomy.org/?id=7051">7051</a></td></tr><tr><th scope="row" class="infobox-label" style="padding-right:0.25em"><a href="/wiki/Terminologia_Histologica" title="Terminologia Histologica">TH</a></th><td class="infobox-data"><a rel="nofollow" class="external text" href="https://ifaa.unifr.ch/Public/EntryPage/PDF/TH%20Chapter%20H3.12.pdf">H3.12.00.3.01041 </a></td></tr><tr><th scope="row" class="infobox-label" style="padding-right:0.25em"><a href="/wiki/Foundational_Model_of_Anatomy" title="Foundational Model of Anatomy">FMA</a></th><td class="infobox-data"><a rel="nofollow" class="external text" href="https://bioportal.bioontology.org/ontologies/FMA/?p=classes&conceptid=http%3A%2F%2Fpurl.org%2Fsig%2Font%2Ffma%2Ffma67821">67821</a></td></tr><tr><td colspan="2" class="infobox-below"><a href="/wiki/Anatomical_terms_of_muscle" title="Anatomical terms of muscle">Anatomical terms of muscle</a><div style="text-align: right;"><small class="noprint">[<a href="https://www.wikidata.org/wiki/Q1954107" class="extiw" title="d:Q1954107">edit on Wikidata</a>]</small></div></td></tr></tbody></table> <p>The <b>arrector pili muscles</b>, also known as <b>hair erector muscles</b>,<sup id="cite_ref-:4_1-0" class="reference"><a href="#cite_note-:4-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> are small muscles attached to <a href="/wiki/Hair_follicles" class="mw-redirect" title="Hair follicles">hair follicles</a> in <a href="/wiki/Mammals" class="mw-redirect" title="Mammals">mammals</a>. Contraction of these muscles causes the hairs to stand on end,<sup id="cite_ref-Cormack2001_2-0" class="reference"><a href="#cite_note-Cormack2001-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> known colloquially as <a href="/wiki/Goose_bumps" title="Goose bumps">goose bumps</a> (piloerection).<sup id="cite_ref-:0_3-0" class="reference"><a href="#cite_note-:0-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Structure">Structure</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=1" title="Edit section: Structure"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Each arrector pili is composed of a bundle of <a href="/wiki/Smooth_muscle" title="Smooth muscle">smooth muscle</a> fibres which attach to several follicles (a follicular unit).<sup id="cite_ref-:1_4-0" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Each is innervated by the sympathetic division of the <a href="/wiki/Autonomic_nervous_system" title="Autonomic nervous system">autonomic nervous system</a>.<sup id="cite_ref-:1_4-1" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The muscle attaches to the follicular stem cell niche in the follicular bulge,<sup id="cite_ref-:0_3-1" class="reference"><a href="#cite_note-:0-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:1_4-2" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:2_5-0" class="reference"><a href="#cite_note-:2-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> splitting at their deep end to encircle the follicle.<sup id="cite_ref-:3_6-0" class="reference"><a href="#cite_note-:3-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Function">Function</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=2" title="Edit section: Function"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The contraction of the muscle is involuntary. Stresses such as <a href="/wiki/Cold" title="Cold">cold</a>, <a href="/wiki/Fear" title="Fear">fear</a> etc. may stimulate the <a href="/wiki/Sympathetic_nervous_system" title="Sympathetic nervous system">sympathetic nervous system</a>, and thus cause muscle contraction.<sup id="cite_ref-:1_4-3" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Thermal_insulation">Thermal insulation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=3" title="Edit section: Thermal insulation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Contraction of arrector pili muscles have a principal function in the majority of mammals of providing thermal insulation.<sup id="cite_ref-:1_4-4" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Air becomes trapped between the erect hairs, helping the animal retain heat. </p> <div class="mw-heading mw-heading3"><h3 id="Self_defence">Self defence</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=4" title="Edit section: Self defence"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Many animals experience contraction of the arrector pili muscle in response to a perceived threat. This helps the animal seem more larger and more intimidating as a result.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Sebum_excretion">Sebum excretion</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=5" title="Edit section: Sebum excretion"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Pressure exerted by the muscle may cause <a href="/wiki/Sebum" class="mw-redirect" title="Sebum">sebum</a> to be forced along the hair follicle towards the surface, protecting the hair.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Hair_follicle_stability">Hair follicle stability</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=6" title="Edit section: Hair follicle stability"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Arrector pili muscles also stabilise the base of the <a href="/wiki/Hair_follicle" title="Hair follicle">hair follicle</a>.<sup id="cite_ref-:2_5-1" class="reference"><a href="#cite_note-:2-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:3_6-1" class="reference"><a href="#cite_note-:3-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Clinical_significance">Clinical significance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=7" title="Edit section: Clinical significance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Skin conditions such as <a href="/wiki/Leprosy" title="Leprosy">leprosy</a> can damage arrector pili muscles, preventing their contraction.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Inducing contraction of the arrector pili muscles via an <a href="/wiki/Alpha-1_adrenergic_receptor" title="Alpha-1 adrenergic receptor">α1-adrenergic receptor</a> agonist has been shown to reduce hair shedding as a result of <a href="/wiki/Traction_alopecia" title="Traction alopecia">traction alopecia</a><sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=8" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The term "arrector pili" comes from Latin. It translates to "hair erector".<sup id="cite_ref-:4_1-1" class="reference"><a href="#cite_note-:4-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Additional_images">Additional images</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=9" title="Edit section: Additional images"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul class="gallery mw-gallery-traditional"> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Insertion_of_sebaceous_glands_into_hair_shaft_x10.jpg" class="mw-file-description" title="Insertion of sebaceous glands into hair shaft"><img alt="Insertion of sebaceous glands into hair shaft" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Insertion_of_sebaceous_glands_into_hair_shaft_x10.jpg/120px-Insertion_of_sebaceous_glands_into_hair_shaft_x10.jpg" decoding="async" width="120" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Insertion_of_sebaceous_glands_into_hair_shaft_x10.jpg/180px-Insertion_of_sebaceous_glands_into_hair_shaft_x10.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Insertion_of_sebaceous_glands_into_hair_shaft_x10.jpg/240px-Insertion_of_sebaceous_glands_into_hair_shaft_x10.jpg 2x" data-file-width="2048" data-file-height="1536" /></a></span></div> <div class="gallerytext">Insertion of <a href="/wiki/Sebaceous_glands" class="mw-redirect" title="Sebaceous glands">sebaceous glands</a> into <a href="/wiki/Hair_shaft" class="mw-redirect" title="Hair shaft">hair shaft</a></div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Skin.png" class="mw-file-description" title="Cross-section of all skin layers"><img alt="Cross-section of all skin layers" src="//upload.wikimedia.org/wikipedia/commons/thumb/2/27/Skin.png/117px-Skin.png" decoding="async" width="117" height="120" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/27/Skin.png/175px-Skin.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/27/Skin.png/233px-Skin.png 2x" data-file-width="1000" data-file-height="1029" /></a></span></div> <div class="gallerytext">Cross-section of all <a href="/wiki/Skin_layers" class="mw-redirect" title="Skin layers">skin layers</a></div> </li> </ul> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Arrector_pili_muscle&action=edit&section=10" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-:4-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-:4_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:4_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://training.seer.cancer.gov/melanoma/anatomy/">"Anatomy of the Skin | SEER Training"</a>. <i>training.seer.cancer.gov</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2021-01-21</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=training.seer.cancer.gov&rft.atitle=Anatomy+of+the+Skin+%7C+SEER+Training&rft_id=https%3A%2F%2Ftraining.seer.cancer.gov%2Fmelanoma%2Fanatomy%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AArrector+pili+muscle" class="Z3988"></span></span> </li> <li id="cite_note-Cormack2001-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-Cormack2001_2-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDavid_H._Cormack2001" class="citation book cs1">David H. Cormack (1 June 2001). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/essentialhistolo0000corm_p5i3"><i>Essential histology</i></a></span>. Lippincott Williams & Wilkins. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/essentialhistolo0000corm_p5i3/page/1">1</a>–. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7817-1668-0" title="Special:BookSources/978-0-7817-1668-0"><bdi>978-0-7817-1668-0</bdi></a><span class="reference-accessdate">. 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Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web; <a rel="nofollow" class="external free" href="https://web.archive.org/web/20110903154915/http://animaldiversity.ummz.umich.edu/site/topics/mammal_anatomy/hair.html">https://web.archive.org/web/20110903154915/http://animaldiversity.ummz.umich.edu/site/topics/mammal_anatomy/hair.html</a></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBurkitt,_Young1993" class="citation book cs1">Burkitt, Young; et al. (1993). <i>Wheater's Functional Histology: a text and colour atlas</i>. 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aria-labelledby="Skin_and_related_structures" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini 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adiposus</a></li> <li><a href="/wiki/Panniculus_carnosus" title="Panniculus carnosus">Panniculus carnosus</a>)</li> <li><a href="/wiki/Membranous_layer" title="Membranous layer">Membranous layer</a></li> <li><a href="/wiki/Loose_connective_tissue" title="Loose connective tissue">Loose connective tissue</a></li> <li><a href="/wiki/Superficial_fascia" class="mw-redirect" title="Superficial fascia">Superficial fascia</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Skin_appendage" title="Skin appendage">Adnexa</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Skin_gland" class="mw-redirect" title="Skin gland">Skin glands</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Sweat_gland" title="Sweat gland">Sweat glands</a>: <a href="/wiki/Apocrine_sweat_gland" title="Apocrine sweat gland">Apocrine sweat gland</a></li> <li><a href="/wiki/Eccrine_sweat_gland" title="Eccrine sweat gland">Eccrine sweat gland</a></li> <li><a href="/wiki/Sebaceous_gland" title="Sebaceous gland">Sebaceous</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Hair" title="Hair">Hair</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Root_sheath_(hair)" title="Root sheath (hair)">Root sheath</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Outer_root_sheath" title="Outer root sheath">Outer root sheath</a></li> <li><a href="/wiki/Inner_root_sheath" title="Inner root sheath">Inner root sheath</a> <ul><li><a href="/wiki/Henle%27s_layer" title="Henle's layer">Henle's layer</a></li> <li><a href="/wiki/Huxley%27s_layer" title="Huxley's layer">Huxley's layer</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Hair_shaft" class="mw-redirect" title="Hair shaft">Hair shaft</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cuticle_(hair)" title="Cuticle (hair)">Cuticle</a></li> <li><a href="/wiki/Cortex_(hair)" title="Cortex (hair)">Cortex</a></li> <li><a href="/wiki/Medulla_(hair)" title="Medulla (hair)">Medulla</a></li> <li><a href="/wiki/Matrix_(hair)" class="mw-redirect" title="Matrix (hair)">Bulb with matrix cells</a></li> <li><a href="/wiki/Hair_follicle" title="Hair follicle">Hair follicle</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Muscle" title="Muscle">Muscle</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a class="mw-selflink selflink">Arrector pili muscle</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Pilosebaceous_unit" class="mw-redirect" title="Pilosebaceous unit">Pilosebaceous unit</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Hair <a href="/wiki/Sebaceous_gland" title="Sebaceous gland">sebaceous gland</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Nail_(anatomy)" title="Nail (anatomy)">Nail</a></th><td class="navbox-list-with-group navbox-list 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