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<a class="vector-toc-link" href="#Implantation"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.4</span> <span>Implantation</span> </div> </a> <ul id="toc-Implantation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Embryonic_disc" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Embryonic_disc"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.5</span> <span>Embryonic disc</span> </div> </a> <ul id="toc-Embryonic_disc-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Gastrulation" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Gastrulation"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Gastrulation</span> </div> </a> <ul id="toc-Gastrulation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Neurulation" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Neurulation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Neurulation</span> </div> </a> <ul id="toc-Neurulation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Development_of_organs_and_organ_systems" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Development_of_organs_and_organ_systems"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Development of organs and organ systems</span> </div> </a> <button aria-controls="toc-Development_of_organs_and_organ_systems-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 Development of organs and organ systems subsection</span> </button> <ul id="toc-Development_of_organs_and_organ_systems-sublist" class="vector-toc-list"> <li id="toc-Blood" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Blood"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Blood</span> </div> </a> <ul id="toc-Blood-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Heart_and_circulatory_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Heart_and_circulatory_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Heart and circulatory system</span> </div> </a> <ul id="toc-Heart_and_circulatory_system-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Digestive_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Digestive_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3</span> <span>Digestive system</span> </div> </a> <ul id="toc-Digestive_system-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Respiratory_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Respiratory_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.4</span> <span>Respiratory system</span> </div> </a> <ul id="toc-Respiratory_system-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Urinary_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Urinary_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5</span> <span>Urinary system</span> </div> </a> <ul id="toc-Urinary_system-sublist" class="vector-toc-list"> <li id="toc-Kidneys" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Kidneys"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5.1</span> <span>Kidneys</span> </div> </a> <ul id="toc-Kidneys-sublist" class="vector-toc-list"> <li id="toc-Pronephros" class="vector-toc-list-item vector-toc-level-4"> <a class="vector-toc-link" href="#Pronephros"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5.1.1</span> <span>Pronephros</span> </div> </a> <ul id="toc-Pronephros-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Mesonephros" class="vector-toc-list-item vector-toc-level-4"> <a class="vector-toc-link" href="#Mesonephros"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5.1.2</span> <span>Mesonephros</span> </div> </a> <ul id="toc-Mesonephros-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Metanephros" class="vector-toc-list-item vector-toc-level-4"> <a class="vector-toc-link" href="#Metanephros"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5.1.3</span> <span>Metanephros</span> </div> </a> <ul id="toc-Metanephros-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Bladder_and_urethra" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Bladder_and_urethra"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5.2</span> <span>Bladder and urethra</span> </div> </a> <ul id="toc-Bladder_and_urethra-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Reproductive_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Reproductive_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.6</span> <span>Reproductive system</span> </div> </a> <ul id="toc-Reproductive_system-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Integumentary_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Integumentary_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.7</span> <span>Integumentary system</span> </div> </a> <ul id="toc-Integumentary_system-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Nervous_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Nervous_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.8</span> <span>Nervous system</span> </div> </a> <ul id="toc-Nervous_system-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Development_of_physical_features" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Development_of_physical_features"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Development of physical features</span> </div> </a> <button aria-controls="toc-Development_of_physical_features-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 Development of physical features subsection</span> </button> <ul id="toc-Development_of_physical_features-sublist" class="vector-toc-list"> <li id="toc-Face_and_neck" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Face_and_neck"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Face and neck</span> </div> </a> <ul id="toc-Face_and_neck-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Ears" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Ears"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Ears</span> </div> </a> <ul id="toc-Ears-sublist" class="vector-toc-list"> <li id="toc-Inner_ear" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Inner_ear"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2.1</span> <span>Inner ear</span> </div> </a> <ul id="toc-Inner_ear-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Middle_ear" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Middle_ear"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2.2</span> <span>Middle ear</span> </div> </a> <ul id="toc-Middle_ear-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Outer_ear" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Outer_ear"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2.3</span> <span>Outer ear</span> </div> </a> <ul id="toc-Outer_ear-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Eyes" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Eyes"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Eyes</span> </div> </a> <ul id="toc-Eyes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Limbs" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Limbs"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.4</span> <span>Limbs</span> </div> </a> <ul id="toc-Limbs-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Clinical_significance" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Clinical_significance"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Clinical significance</span> </div> </a> <ul id="toc-Clinical_significance-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Additional_images" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Additional_images"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Additional images</span> </div> </a> <ul id="toc-Additional_images-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Human embryonic development</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 20 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-20" 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">20 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/%D9%85%D8%B1%D8%A7%D8%AD%D9%84_%D8%AA%D8%B7%D9%88%D8%B1_%D8%A7%D9%84%D8%AC%D9%86%D9%8A%D9%86_%D8%A7%D9%84%D8%A8%D8%B4%D8%B1%D9%8A" title="مراحل تطور الجنين البشري – Arabic" lang="ar" hreflang="ar" data-title="مراحل تطور الجنين البشري" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/%C4%B0nsan_embriogenezi" title="İnsan embriogenezi – Azerbaijani" lang="az" hreflang="az" data-title="İnsan embriogenezi" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%97%D0%B0%D1%80%D0%BE%D0%B4%D0%B8%D1%88%D0%BD%D0%BE_%D1%80%D0%B0%D0%B7%D0%B2%D0%B8%D1%82%D0%B8%D0%B5" title="Зародишно развитие – Bulgarian" lang="bg" hreflang="bg" data-title="Зародишно развитие" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Embryon%C3%A1ln%C3%AD_v%C3%BDvoj_%C4%8Dlov%C4%9Bka" title="Embryonální vývoj člověka – Czech" lang="cs" hreflang="cs" data-title="Embryonální vývoj člověka" 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/Embryogenese_(Mensch)" title="Embryogenese (Mensch) – German" lang="de" hreflang="de" data-title="Embryogenese (Mensch)" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Embriog%C3%A9nesis_humana" title="Embriogénesis humana – Spanish" lang="es" hreflang="es" data-title="Embriogénesis humana" 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/%D8%AA%DA%A9%D9%88%DB%8C%D9%86_%D8%B1%D9%88%DB%8C%D8%A7%D9%86_%D8%A7%D9%86%D8%B3%D8%A7%D9%86" title="تکوین رویان انسان – Persian" lang="fa" hreflang="fa" data-title="تکوین رویان انسان" 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/Embryogen%C3%A8se_humaine" title="Embryogenèse humaine – French" lang="fr" hreflang="fr" data-title="Embryogenèse humaine" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Embriox%C3%A9nese_humana" title="Embrioxénese humana – Galician" lang="gl" hreflang="gl" data-title="Embrioxénese humana" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%AE%E0%A4%BE%E0%A4%A8%E0%A4%B5_%E0%A4%AD%E0%A5%8D%E0%A4%B0%E0%A5%82%E0%A4%A3_%E0%A4%B5%E0%A4%BF%E0%A4%95%E0%A4%BE%E0%A4%B8" title="मानव भ्रूण विकास – Hindi" lang="hi" hreflang="hi" data-title="मानव भ्रूण विकास" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Humana_embriogeneza" title="Humana embriogeneza – Croatian" lang="hr" hreflang="hr" data-title="Humana embriogeneza" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Perkembangan_embrionik_manusia" title="Perkembangan embrionik manusia – Indonesian" lang="id" hreflang="id" data-title="Perkembangan embrionik manusia" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%94%D7%AA%D7%A4%D7%AA%D7%97%D7%95%D7%AA_%D7%A2%D7%95%D7%91%D7%A8_%D7%94%D7%90%D7%93%D7%9D" title="התפתחות עובר האדם – Hebrew" lang="he" hreflang="he" data-title="התפתחות עובר האדם" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/%C5%BDmogaus_gemalas" title="Žmogaus gemalas – Lithuanian" lang="lt" hreflang="lt" data-title="Žmogaus gemalas" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Embriog%C3%A9nese_humana" title="Embriogénese humana – Portuguese" lang="pt" hreflang="pt" data-title="Embriogénese humana" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%AD%D0%BC%D0%B1%D1%80%D0%B8%D0%BE%D0%B3%D0%B5%D0%BD%D0%B5%D0%B7_%D1%87%D0%B5%D0%BB%D0%BE%D0%B2%D0%B5%D0%BA%D0%B0" title="Эмбриогенез человека – Russian" lang="ru" hreflang="ru" data-title="Эмбриогенез человека" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/Embriologija_%C4%8Doveka" title="Embriologija čoveka – Serbian" lang="sr" hreflang="sr" data-title="Embriologija čoveka" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%81%E0%B8%B2%E0%B8%A3%E0%B9%80%E0%B8%81%E0%B8%B4%E0%B8%94%E0%B9%80%E0%B8%AD%E0%B9%87%E0%B8%A1%E0%B8%9A%E0%B8%A3%E0%B8%B4%E0%B9%82%E0%B8%AD%E0%B8%A1%E0%B8%99%E0%B8%B8%E0%B8%A9%E0%B8%A2%E0%B9%8C" title="การเกิดเอ็มบริโอมนุษย์ – Thai" lang="th" hreflang="th" data-title="การเกิดเอ็มบริโอมนุษย์" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%95%D0%BC%D0%B1%D1%80%D1%96%D0%BE%D0%BD%D0%B0%D0%BB%D1%8C%D0%BD%D0%B8%D0%B9_%D1%80%D0%BE%D0%B7%D0%B2%D0%B8%D1%82%D0%BE%D0%BA_%D0%BB%D1%8E%D0%B4%D0%B8%D0%BD%D0%B8" title="Ембріональний розвиток людини – Ukrainian" lang="uk" hreflang="uk" data-title="Ембріональний розвиток людини" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E4%BA%BA%E9%A1%9E%E8%83%9A%E8%83%8E%E7%99%BC%E8%82%B2" title="人類胚胎發育 – Chinese" lang="zh" hreflang="zh" data-title="人類胚胎發育" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q964797#sitelinks-wikipedia" title="Edit 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.hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">This article is about human embryonic development. For embryonic development in general, see <a href="/wiki/Embryonic_development" class="mw-redirect" title="Embryonic development">Embryonic development</a>.</div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:HumanEmbryogenesis.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/06/HumanEmbryogenesis.svg/400px-HumanEmbryogenesis.svg.png" decoding="async" width="400" height="313" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/06/HumanEmbryogenesis.svg/600px-HumanEmbryogenesis.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/06/HumanEmbryogenesis.svg/800px-HumanEmbryogenesis.svg.png 2x" data-file-width="1560" data-file-height="1220" /></a><figcaption>The initial stages of human embryonic development (<a href="/wiki/Embryogenesis" class="mw-redirect" title="Embryogenesis">embryogenesis</a>)</figcaption></figure> <style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist 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.sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><style data-mw-deduplicate="TemplateStyles:r1040468660">.mw-parser-output .human-growth-dev-sidebar .sidebar-title-with-pretitle{background-color:#ccf}.mw-parser-output .human-growth-dev-sidebar .sidebar-heading{background-color:#ddf}.mw-parser-output .human-growth-dev-sidebar .sidebar-below{border-top:1px solid #aaa;border-bottom:1px solid #aaa}</style><table class="sidebar nomobile nowraplinks hlist human-growth-dev-sidebar"><tbody><tr><td class="sidebar-pretitle">Part of <a href="/wiki/Category:Human_development" title="Category:Human development">a series</a> on</td></tr><tr><th class="sidebar-title-with-pretitle"><a href="/wiki/Development_of_the_human_body" title="Development of the human body">Human growth<br />and development</a></th></tr><tr><td class="sidebar-image"><span typeof="mw:File"><a href="/wiki/File:Views_of_a_Foetus_in_the_Womb_detail.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Views_of_a_Foetus_in_the_Womb_detail.jpg/100px-Views_of_a_Foetus_in_the_Womb_detail.jpg" decoding="async" width="100" height="139" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Views_of_a_Foetus_in_the_Womb_detail.jpg/150px-Views_of_a_Foetus_in_the_Womb_detail.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Views_of_a_Foetus_in_the_Womb_detail.jpg/200px-Views_of_a_Foetus_in_the_Womb_detail.jpg 2x" data-file-width="400" data-file-height="556" /></a></span></td></tr><tr><th class="sidebar-heading"> Stages</th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Gamete" title="Gamete">Gamete</a></li> <li><a href="/wiki/Zygote" title="Zygote">Zygote</a></li> <li><a class="mw-selflink selflink">Embryo</a></li> <li><a href="/wiki/Fetus" title="Fetus">Fetus</a><br /></li> <li><a href="/wiki/Infant" title="Infant">Infant</a></li> <li><a href="/wiki/Toddler" title="Toddler">Toddler</a><br /></li> <li><a href="/wiki/Child" title="Child">Child</a></li> <li><a href="/wiki/Preadolescence" title="Preadolescence">Preadolescent</a></li> <li><a href="/wiki/Adolescence" title="Adolescence">Adolescent</a><br /></li> <li><a href="/wiki/Emerging_adulthood_and_early_adulthood" title="Emerging adulthood and early adulthood">Emerging and early adulthood</a></li> <li><a href="/wiki/Young_adult" title="Young adult">Young adult</a></li> <li><a href="/wiki/Middle_age" title="Middle age">Middle adult</a></li> <li><a href="/wiki/Old_age" title="Old age">Old adult</a></li> <li><a href="/wiki/Dying" title="Dying">Dying</a></li></ul></td> </tr><tr><th class="sidebar-heading"> Biological milestones</th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Human_fertilization" title="Human fertilization">Fertilization</a></li> <li><a href="/wiki/Pregnancy" title="Pregnancy">Pregnancy</a></li> <li><a href="/wiki/Childbirth" title="Childbirth">Childbirth</a></li> <li><a href="/wiki/Gross_motor_skill#Learning_to_walk" title="Gross motor skill">Walking</a></li> <li><a href="/wiki/Language_acquisition" title="Language acquisition">Language acquisition</a></li> <li><a href="/wiki/Puberty" title="Puberty">Puberty</a></li> <li><a href="/wiki/Menopause" title="Menopause">Menopause</a></li> <li><a href="/wiki/Ageing" title="Ageing">Ageing</a></li> <li><a href="/wiki/Death" title="Death">Death</a></li></ul></td> </tr><tr><th class="sidebar-heading"> <a href="/wiki/Developmental_psychology" title="Developmental psychology">Development and psychology</a></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Prenatal_and_perinatal_psychology" title="Prenatal and perinatal psychology">Pre- and perinatal</a></li> <li><a href="/wiki/Child_development_stages" title="Child development stages">Infant and child</a></li> <li><a href="/wiki/Nature_versus_nurture" title="Nature versus nurture">Nature versus nurture</a></li> <li><a href="/wiki/Adolescence#psychology" title="Adolescence">Adolescent</a></li> <li><a href="/wiki/Positive_youth_development" title="Positive youth development">Youth</a></li> <li><a href="/wiki/Young_adult" title="Young adult">Young adult</a></li> <li><a href="/wiki/Adult_development" title="Adult development">Adult</a></li> <li><a href="/wiki/Maturity_(psychological)" title="Maturity (psychological)">Maturity</a></li></ul></td> </tr><tr><th class="sidebar-heading"> <div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Developmental_stage_theories" title="Developmental stage theories">Developmental stage theories</a></div></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Attachment_theory" title="Attachment theory">Attachment</a></li> <li><a href="/wiki/Ecological_systems_theory" title="Ecological systems theory">Ecological</a></li> <li><a href="/wiki/Erikson%27s_stages_of_psychosocial_development" title="Erikson's stages of psychosocial development">Psychosocial</a></li> <li><a href="/wiki/Psychosexual_development" title="Psychosexual development">Psychosexual development</a></li> <li><a href="/wiki/Lawrence_Kohlberg%27s_stages_of_moral_development" title="Lawrence Kohlberg's stages of moral development">Moral</a></li> <li><a href="/wiki/Piaget%27s_theory_of_cognitive_development" title="Piaget's theory of cognitive development">Cognitive</a></li> <li><a href="/wiki/Cultural-historical_psychology" title="Cultural-historical psychology">Cultural-historical</a></li> <li><a href="/wiki/Evolutionary_developmental_psychology" title="Evolutionary developmental psychology">Evolutionary</a></li></ul></td> </tr><tr><td class="sidebar-below"> <ul><li><span class="nowrap"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Psi2.svg/16px-Psi2.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Psi2.svg/24px-Psi2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Psi2.svg/32px-Psi2.svg.png 2x" data-file-width="100" data-file-height="100" /></span></span> </span><a href="/wiki/Portal:Psychology" title="Portal:Psychology">Psychology portal</a></li></ul></td></tr><tr><td class="sidebar-navbar"><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 abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Human_growth_and_development_sidebar" title="Template:Human growth and development sidebar"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Human_growth_and_development_sidebar" title="Template talk:Human growth and development sidebar"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Human_growth_and_development_sidebar" title="Special:EditPage/Template:Human growth and development sidebar"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <p><b>Human embryonic development</b> or <b>human embryogenesis</b> is the development and formation of the human <a href="/wiki/Embryo" title="Embryo">embryo</a>. It is characterised by the processes of <a href="/wiki/Cell_division" title="Cell division">cell division</a> and <a href="/wiki/Cellular_differentiation" title="Cellular differentiation">cellular differentiation</a> of the embryo that occurs during the early stages of development. In biological terms, the <a href="/wiki/Development_of_the_human_body" title="Development of the human body">development of the human body</a> entails growth from a one-celled <a href="/wiki/Zygote" title="Zygote">zygote</a> to an adult <a href="/wiki/Human_being" class="mw-redirect" title="Human being">human being</a>. <a href="/wiki/Human_fertilization" title="Human fertilization">Fertilization</a> occurs when the <a href="/wiki/Spermatozoon" title="Spermatozoon">sperm cell</a> successfully enters and <a href="/wiki/Cell_fusion" title="Cell fusion">fuses</a> with an <a href="/wiki/Egg_cell" title="Egg cell">egg cell</a> (ovum). The genetic material of the sperm and egg then combine to form the single cell zygote and the germinal stage of development commences. Human embryonic development covers the first eight weeks of development, which have 23 stages, called <a href="/wiki/Carnegie_stages" title="Carnegie stages">Carnegie stages</a>. At the beginning of the ninth week, the embryo is termed a <a href="/wiki/Fetus" title="Fetus">fetus</a> (spelled "foetus" in <a href="/wiki/British_English" title="British English">British English</a>). In comparison to the embryo, the fetus has more recognizable external features and a more complete set of developing organs. </p><p><b>Human embryology</b> is the study of this development during the first eight weeks after fertilization. The normal period of <a href="/wiki/Gestation" title="Gestation">gestation</a> (pregnancy) is about nine months or 36 weeks. </p><p>The germinal stage refers to the time from fertilization through the development of the early embryo until <a href="/wiki/Implantation_(embryology)" title="Implantation (embryology)">implantation</a> is completed in the <a href="/wiki/Uterus" title="Uterus">uterus</a>. The germinal stage takes around 10 days.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> During this stage, the zygote divides in a process called <a href="/wiki/Cleavage_(embryo)" title="Cleavage (embryo)">cleavage</a>. A <a href="/wiki/Blastocyst" title="Blastocyst">blastocyst</a> is then formed and implants in the <a href="/wiki/Uterus" title="Uterus">uterus</a>. Embryogenesis continues with the next stage of <a href="/wiki/Gastrulation" title="Gastrulation">gastrulation</a>, when the three <a href="/wiki/Germ_layers" class="mw-redirect" title="Germ layers">germ layers</a> of the embryo form in a process called <a href="/wiki/Histogenesis" title="Histogenesis">histogenesis</a>, and the processes of <a href="/wiki/Neurulation" title="Neurulation">neurulation</a> and <a href="/wiki/Organogenesis" title="Organogenesis">organogenesis</a> follow. </p><p>The entire process of embryogenesis involves coordinated spatial and temporal changes in <a href="/wiki/Gene_expression" title="Gene expression">gene expression</a>, <a href="/wiki/Cell_growth" title="Cell growth">cell growth</a>, and <a href="/wiki/Cellular_differentiation" title="Cellular differentiation">cellular differentiation</a>. A nearly identical process occurs in other species, especially among <a href="/wiki/Chordate" title="Chordate">chordates</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Germinal_stage">Germinal stage</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=1" title="Edit section: Germinal stage"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Fertilization">Fertilization</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=2" title="Edit section: Fertilization"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Human_fertilization" title="Human fertilization">Human fertilization</a></div> <p>Fertilization takes place when the <a href="/wiki/Spermatozoon" title="Spermatozoon">spermatozoon</a> has successfully entered the ovum and the two sets of genetic material carried by the <a href="/wiki/Gamete" title="Gamete">gametes</a> fuse together, resulting in the zygote (a single <a href="/wiki/Diploid" class="mw-redirect" title="Diploid">diploid</a> cell). This usually takes place in the ampulla of one of the <a href="/wiki/Fallopian_tube" title="Fallopian tube">fallopian tubes</a>. The zygote contains the combined genetic material carried by both the male and female gametes which consists of the 23 chromosomes from the nucleus of the ovum and the 23 chromosomes from the nucleus of the sperm. The 46 chromosomes undergo changes prior to the <a href="/wiki/Mitotic_division" class="mw-redirect" title="Mitotic division">mitotic division</a> which leads to the formation of the embryo having two cells. </p><p>Successful fertilization is enabled by three processes, which also act as controls to ensure species-specificity. The first is that of <a href="/wiki/Chemotaxis" title="Chemotaxis">chemotaxis</a> which directs the movement of the sperm towards the ovum.<sup id="cite_ref-Marlow_2-0" class="reference"><a href="#cite_note-Marlow-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Secondly, an adhesive compatibility between the sperm and the egg occurs. With the sperm adhered to the ovum, the third process of <a href="/wiki/Acrosomal_reaction" class="mw-redirect" title="Acrosomal reaction">acrosomal reaction</a> takes place; the front part of the spermatozoan head is capped by an <a href="/wiki/Acrosome" title="Acrosome">acrosome</a> which contains digestive <a href="/wiki/Enzyme" title="Enzyme">enzymes</a> to break down the <a href="/wiki/Zona_pellucida" title="Zona pellucida">zona pellucida</a> and allow its entry.<sup id="cite_ref-Singh_3-0" class="reference"><a href="#cite_note-Singh-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The entry of the sperm causes calcium to be released which blocks entry to other sperm cells.<sup id="cite_ref-Singh_3-1" class="reference"><a href="#cite_note-Singh-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> A parallel reaction takes place in the ovum called the <a href="/wiki/Zona_reaction" class="mw-redirect" title="Zona reaction">zona reaction</a>. This sees the release of <a href="/wiki/Cortical_granule" title="Cortical granule">cortical granules</a> that release enzymes which digest sperm receptor proteins, thus preventing <a href="/wiki/Polyspermy" title="Polyspermy">polyspermy</a>.<sup id="cite_ref-Standring_4-0" class="reference"><a href="#cite_note-Standring-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The granules also fuse with the plasma membrane and modify the zona pellucida in such a way as to prevent further sperm entry. </p> <div class="mw-heading mw-heading3"><h3 id="Cleavage">Cleavage</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=3" title="Edit section: Cleavage"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Cleavage_(embryo)" title="Cleavage (embryo)">Cleavage (embryo)</a> and <a href="/wiki/Cleavage_furrow" title="Cleavage furrow">Cleavage furrow</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Embryo,_8_cells.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Embryo%2C_8_cells.jpg/200px-Embryo%2C_8_cells.jpg" decoding="async" width="200" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Embryo%2C_8_cells.jpg/300px-Embryo%2C_8_cells.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Embryo%2C_8_cells.jpg/400px-Embryo%2C_8_cells.jpg 2x" data-file-width="640" data-file-height="480" /></a><figcaption>Eight-cell embryo, at three days</figcaption></figure> <p>The beginning of the <a href="/wiki/Cleavage_(embryo)" title="Cleavage (embryo)">cleavage</a> process is marked when the zygote divides through <a href="/wiki/Mitosis" title="Mitosis">mitosis</a> into two cells. This mitosis continues and the first two cells divide into four cells, then into eight cells and so on. Each division takes from 12 to 24 hours. The zygote is large compared to any other cell and undergoes cleavage without any overall increase in size. This means that with each successive subdivision, the ratio of nuclear to cytoplasmic material increases.<sup id="cite_ref-Cambridge_University_Press_5-0" class="reference"><a href="#cite_note-Cambridge_University_Press-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>Initially, the dividing cells, called <a href="/wiki/Blastomeres" class="mw-redirect" title="Blastomeres">blastomeres</a> (<span title="Ancient Greek (to 1453)-language romanization"><i lang="grc-Latn">blastos</i></span> Greek for sprout), are undifferentiated and aggregated into a sphere enclosed within the <a href="/wiki/Zona_pellucida" title="Zona pellucida">zona pellucida</a> of the ovum. When eight <a href="/wiki/Blastomere" title="Blastomere">blastomeres</a> have formed, they start to <a href="/wiki/Cleavage_(embryo)#Compaction" title="Cleavage (embryo)">compact</a>.<sup id="cite_ref-Standring2_6-0" class="reference"><a href="#cite_note-Standring2-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> They begin to develop <a href="/wiki/Gap_junction" title="Gap junction">gap junctions</a>, enabling them to develop in an integrated way and co-ordinate their response to physiological signals and environmental cues.<sup id="cite_ref-BrisonSturmey2014_7-0" class="reference"><a href="#cite_note-BrisonSturmey2014-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>When the cells number around sixteen, the solid sphere of cells within the zona pellucida is referred to as a <a href="/wiki/Morula" class="mw-redirect" title="Morula">morula</a>.<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="Blastulation">Blastulation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=4" title="Edit section: Blastulation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Polarity_in_embryogenesis" title="Polarity in embryogenesis">Polarity in embryogenesis</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Diagram_of_Blastocyst_stage.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Diagram_of_Blastocyst_stage.png/200px-Diagram_of_Blastocyst_stage.png" decoding="async" width="200" height="152" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Diagram_of_Blastocyst_stage.png/300px-Diagram_of_Blastocyst_stage.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Diagram_of_Blastocyst_stage.png/400px-Diagram_of_Blastocyst_stage.png 2x" data-file-width="671" data-file-height="509" /></a><figcaption>Blastocyst with an <a href="/wiki/Inner_cell_mass" title="Inner cell mass">inner cell mass</a> and <a href="/wiki/Trophoblast" title="Trophoblast">trophoblast</a></figcaption></figure> <p>Cleavage itself is the first stage in <a href="/wiki/Blastulation" title="Blastulation">blastulation</a>, the process of forming the <a href="/wiki/Blastocyst" title="Blastocyst">blastocyst</a>. Cells differentiate into an outer layer of cells called the <a href="/wiki/Trophoblast" title="Trophoblast">trophoblast</a>, and an <a href="/wiki/Inner_cell_mass" title="Inner cell mass">inner cell mass</a>. With further compaction the individual outer blastomeres, the trophoblasts, become indistinguishable. They are still enclosed within the <a href="/wiki/Zona_pellucida" title="Zona pellucida">zona pellucida</a>. This compaction serves to make the structure watertight, containing the fluid that the cells will later secrete. The inner mass of cells differentiate to become <a href="/wiki/Embryoblast" class="mw-redirect" title="Embryoblast">embryoblasts</a> and <a href="/wiki/Polarity_in_embryogenesis" title="Polarity in embryogenesis">polarise</a> at one end. They close together and form <a href="/wiki/Gap_junction" title="Gap junction">gap junctions</a>, which facilitate cellular communication. This polarisation leaves a cavity, the <a href="/wiki/Blastocoel" title="Blastocoel">blastocoel</a>, creating a structure that is now termed the blastocyst. (In animals other than mammals, this is called the <a href="/wiki/Blastula" class="mw-redirect" title="Blastula">blastula</a>). </p><p>The trophoblasts secrete fluid into the blastocoel. The resulting increase in size of the blastocyst causes it to <a href="/wiki/Zona_hatching" class="mw-redirect" title="Zona hatching">hatch</a> through the zona pellucida, which then disintegrates.<sup id="cite_ref-Cambridge_University_Press_5-1" class="reference"><a href="#cite_note-Cambridge_University_Press-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> This process is called <a href="/wiki/Zona_hatching" class="mw-redirect" title="Zona hatching">zona hatching</a> and it takes place on the sixth day of embryo development, immediately before the implantation process. The hatching of the human embryo is supported by proteases secreted by the cells of the blastocyst, which digest proteins of the zona pellucida, giving rise to a hole. Then, due to the rhythmic expansion and contractions of the blastocyst, an increase of the pressure inside the blastocyst itself occurs, the hole expands and finally the blastocyst can emerge from this rigid envelope. </p><p>The inner cell mass will give rise to the <a href="/wiki/Pre-embryo" title="Pre-embryo">pre-embryo</a>,<sup id="cite_ref-opentext_9-0" class="reference"><a href="#cite_note-opentext-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> the <a href="/wiki/Amnion" title="Amnion">amnion</a>, <a href="/wiki/Yolk_sac" title="Yolk sac">yolk sac</a> and <a href="/wiki/Allantois" title="Allantois">allantois</a>, while the fetal part of the <a href="/wiki/Placenta" title="Placenta">placenta</a> will form from the outer trophoblast layer. The embryo plus its <a href="/wiki/Cell_membrane" title="Cell membrane">membranes</a> is called the <a href="/wiki/Conceptus" title="Conceptus">conceptus</a>, and by this stage the conceptus has reached the <a href="/wiki/Uterus" title="Uterus">uterus</a>. The zona pellucida ultimately disappears completely, and the now exposed cells of the trophoblast allow the blastocyst to attach itself to the <a href="/wiki/Endometrium" title="Endometrium">endometrium</a>, where it will <a href="/wiki/Implantation_(human_embryo)" class="mw-redirect" title="Implantation (human embryo)">implant</a>. The formation of the <a href="/wiki/Hypoblast" title="Hypoblast">hypoblast</a> and <a href="/wiki/Epiblast" title="Epiblast">epiblast</a>, which are the two main layers of the bilaminar germ disc, occurs at the beginning of the second week.<sup id="cite_ref-Carlson_10-0" class="reference"><a href="#cite_note-Carlson-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> Both the embryoblast and the trophoblast will turn into two sub-layers.<sup id="cite_ref-Sadler_11-0" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> The inner cells will turn into the hypoblast layer, which will surround the other layer, called the epiblast, and these layers will form the embryonic disc that will develop into the embryo.<sup id="cite_ref-Carlson_10-1" class="reference"><a href="#cite_note-Carlson-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Sadler_11-1" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p>The trophoblast will also develop two sub-layers: the <a href="/wiki/Cytotrophoblast" title="Cytotrophoblast">cytotrophoblast</a>, which is in front of the <a href="/wiki/Syncytiotrophoblast" title="Syncytiotrophoblast">syncytiotrophoblast</a>, which in turn lies within the <a href="/wiki/Endometrium" title="Endometrium">endometrium</a>.<sup id="cite_ref-Carlson_10-2" class="reference"><a href="#cite_note-Carlson-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> Next, another layer called the <a href="/wiki/Heuser%27s_membrane" title="Heuser's membrane">exocoelomic membrane or Heuser's membrane</a> will appear and surround the cytotrophoblast, as well as the primitive yolk sac.<sup id="cite_ref-Sadler_11-2" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> The syncytiotrophoblast will grow and will enter a phase called lacunar stage, in which some vacuoles will appear and be filled by blood in the following days.<sup id="cite_ref-Carlson_10-3" class="reference"><a href="#cite_note-Carlson-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Sadler_11-3" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> The development of the yolk sac starts with the <a href="/wiki/Hypoplasia" title="Hypoplasia">hypoblastic</a> flat cells that form the exocoelomic membrane, which will coat the inner part of the cytotrophoblast to form the primitive yolk sac. An erosion of the endothelial lining of the maternal capillaries by the syncytiotrophoblastic cells results in the formation of the maternal sinusoids from where the blood will begin to penetrate and flow into and through the trophoblastic lacunae to give rise to the uteroplacental circulation.<sup id="cite_ref-Moore_12-0" class="reference"><a href="#cite_note-Moore-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Larsen_13-0" class="reference"><a href="#cite_note-Larsen-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Subsequently, new cells derived from yolk sac will be established between trophoblast and exocoelomic membrane and will give rise to extra-embryonic <a href="/wiki/Mesoderm" title="Mesoderm">mesoderm</a>, which will form the <a href="/wiki/Chorion" title="Chorion">chorionic cavity</a>.<sup id="cite_ref-Sadler_11-4" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p>At the end of the second week of development, some cells of the trophoblast penetrate and form rounded columns into the syncytiotrophoblast. These columns are known as <a href="/wiki/Chorionic_villi" title="Chorionic villi">primary villi</a>. At the same time, other migrating cells form into the exocoelomic cavity a new cavity named the secondary or definitive yolk sac, smaller than the primitive yolk sac.<sup id="cite_ref-Sadler_11-5" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Moore_12-1" class="reference"><a href="#cite_note-Moore-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Implantation">Implantation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=5" title="Edit section: Implantation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Implantation_(embryology)" title="Implantation (embryology)">Implantation (embryology)</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Gray36.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Gray36.png/200px-Gray36.png" decoding="async" width="200" height="142" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Gray36.png/300px-Gray36.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Gray36.png/400px-Gray36.png 2x" data-file-width="450" data-file-height="320" /></a><figcaption>Trophoblast differentiation</figcaption></figure> <p>After <a href="/wiki/Ovulation" title="Ovulation">ovulation</a>, the <a href="/wiki/Endometrium" title="Endometrium">endometrial lining</a> becomes transformed into a secretory lining in preparation of accepting the embryo. It becomes thickened, with its <a href="/wiki/Secretory_gland" class="mw-redirect" title="Secretory gland">secretory glands</a> becoming elongated, and is increasingly <a href="/wiki/Blood_vessel" title="Blood vessel">vascular</a>. This lining of the uterine cavity (or womb) is now known as the <a href="/wiki/Decidua" title="Decidua">decidua</a>, and it produces a great number of large <a href="/wiki/Decidual_cells" title="Decidual cells">decidual cells</a> in its increased interglandular tissue. The blastomeres in the blastocyst are arranged into an outer layer called the <a href="/wiki/Trophoblast" title="Trophoblast">trophoblast</a>. The trophoblast then differentiates into an inner layer, the <a href="/wiki/Cytotrophoblast" title="Cytotrophoblast">cytotrophoblast</a>, and an outer layer, the <a href="/wiki/Syncytiotrophoblast" title="Syncytiotrophoblast">syncytiotrophoblast</a>. The cytotrophoblast contains <a href="/wiki/Cuboidal" class="mw-redirect" title="Cuboidal">cuboidal</a> <a href="/wiki/Epithelial" class="mw-redirect" title="Epithelial">epithelial</a> <a href="/wiki/Cell_(biology)" title="Cell (biology)">cells</a> and is the source of <a href="/wiki/Cell_division" title="Cell division">dividing cells</a>, and the syncytiotrophoblast is a <a href="/wiki/Syncytium" title="Syncytium">syncytial</a> layer without cell boundaries. </p><p>The syncytiotrophoblast implants the blastocyst in the decidual <a href="/wiki/Epithelium" title="Epithelium">epithelium</a> by projections of <a href="/wiki/Chorionic_villi" title="Chorionic villi">chorionic villi</a>, forming the embryonic part of the placenta. The placenta develops once the blastocyst is implanted, connecting the embryo to the uterine wall. The decidua here is termed the decidua basalis; it lies between the blastocyst and the <a href="/wiki/Myometrium" title="Myometrium">myometrium</a> and forms the maternal part of the <a href="/wiki/Placenta" title="Placenta">placenta</a>. The implantation is assisted by <a href="/wiki/Hydrolytic" class="mw-redirect" title="Hydrolytic">hydrolytic</a> <a href="/wiki/Enzyme" title="Enzyme">enzymes</a> that erode the <a href="/wiki/Epithelium" title="Epithelium">epithelium</a>. The <a href="/wiki/Syncytiotrophoblast" title="Syncytiotrophoblast">syncytiotrophoblast</a> also produces <a href="/wiki/Human_chorionic_gonadotropin" title="Human chorionic gonadotropin">human chorionic gonadotropin</a>, a <a href="/wiki/Hormone" title="Hormone">hormone</a> that stimulates the release of <a href="/wiki/Progesterone" title="Progesterone">progesterone</a> from the <a href="/wiki/Corpus_luteum" title="Corpus luteum">corpus luteum</a>. Progesterone enriches the uterus with a thick lining of blood vessels and capillaries so that it can oxygenate and sustain the developing embryo. The uterus liberates sugar from stored <a href="/wiki/Glycogen" title="Glycogen">glycogen</a> from its cells to nourish the <a href="/wiki/Embryo" title="Embryo">embryo</a>.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> The villi begin to branch and contain blood vessels of the embryo. Other villi, called terminal or free villi, exchange nutrients. The embryo is joined to the trophoblastic shell by a narrow connecting stalk that develops into the umbilical cord to attach the placenta to the embryo.<sup id="cite_ref-Sadler_11-6" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Smith_15-0" class="reference"><a href="#cite_note-Smith-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> Arteries in the decidua are remodelled to increase the maternal blood flow into the intervillous spaces of the placenta, allowing <a href="/wiki/Respiration_(physiology)" title="Respiration (physiology)">gas exchange</a> and the transfer of nutrients to the embryo. Waste products from the embryo will diffuse across the placenta. </p><p>As the syncytiotrophoblast starts to penetrate the uterine wall, the inner cell mass (embryoblast) also develops. The inner cell mass is the source of embryonic <a href="/wiki/Stem_cells" class="mw-redirect" title="Stem cells">stem cells</a>, which are <a href="/wiki/Pluripotent" class="mw-redirect" title="Pluripotent">pluripotent</a> and can develop into any one of the three germ layer cells, and which have the potency to give rise to all the tissues and organs. </p> <div class="mw-heading mw-heading3"><h3 id="Embryonic_disc">Embryonic disc</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=6" title="Edit section: Embryonic disc"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The embryoblast forms an <a href="/wiki/Bilaminar_embryonic_disc" title="Bilaminar embryonic disc">embryonic disc</a> of two layers, the upper layer is called the <a href="/wiki/Epiblast" title="Epiblast">epiblast</a> and the lower layer, the <a href="/wiki/Hypoblast" title="Hypoblast">hypoblast</a>. The disc is stretched between what will become the <a href="/wiki/Amniotic_cavity" class="mw-redirect" title="Amniotic cavity">amniotic cavity</a> and the yolk sac. The epiblast is adjacent to the trophoblast and made of columnar cells; the hypoblast is closest to the blastocyst cavity and made of cuboidal cells. The epiblast migrates away from the trophoblast downwards, forming the amniotic cavity, the lining of which is formed from <a href="/wiki/Amnioblasts" class="mw-redirect" title="Amnioblasts">amnioblasts</a> developed from the epiblast. The hypoblast is pushed down and forms the yolk sac (exocoelomic cavity) lining. Some hypoblast cells migrate along the inner cytotrophoblast lining of the blastocoel, secreting an <a href="/wiki/Extracellular_matrix" title="Extracellular matrix">extracellular matrix</a> along the way. These hypoblast cells and extracellular matrix are called <a href="/wiki/Heuser%27s_membrane" title="Heuser's membrane">Heuser's membrane</a> (or the exocoelomic membrane), and they cover the blastocoel to form the yolk sac (or exocoelomic cavity). Cells of the hypoblast migrate along the outer edges of this reticulum and form the extraembryonic mesoderm; this disrupts the extraembryonic reticulum. Soon pockets form in the reticulum, which ultimately coalesce to form the <a href="/wiki/Gestational_sac" title="Gestational sac">chorionic cavity</a> (extraembryonic coelom). </p> <div class="mw-heading mw-heading2"><h2 id="Gastrulation">Gastrulation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=7" title="Edit section: Gastrulation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Gastrulation" title="Gastrulation">Gastrulation</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Germ_layers.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/52/Germ_layers.jpg/650px-Germ_layers.jpg" decoding="async" width="650" height="154" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/52/Germ_layers.jpg/975px-Germ_layers.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/5/52/Germ_layers.jpg 2x" data-file-width="1117" data-file-height="264" /></a><figcaption><a href="/wiki/Histogenesis" title="Histogenesis">Histogenesis</a> of the three germ layers</figcaption></figure> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Ultrasound_of_embryo_at_5_weeks,_colored.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/06/Ultrasound_of_embryo_at_5_weeks%2C_colored.png/200px-Ultrasound_of_embryo_at_5_weeks%2C_colored.png" decoding="async" width="200" height="137" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/06/Ultrasound_of_embryo_at_5_weeks%2C_colored.png/300px-Ultrasound_of_embryo_at_5_weeks%2C_colored.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/06/Ultrasound_of_embryo_at_5_weeks%2C_colored.png/400px-Ultrasound_of_embryo_at_5_weeks%2C_colored.png 2x" data-file-width="743" data-file-height="508" /></a><figcaption>Artificially colored – <a href="/wiki/Gestational_sac" title="Gestational sac">gestational sac</a>, <a href="/wiki/Yolk_sac" title="Yolk sac">yolk sac</a> and <a href="/wiki/Embryo" title="Embryo">embryo</a> (measuring 3 mm at five weeks)</figcaption></figure> <figure typeof="mw:File/Thumb"><a href="/wiki/File:2910_The_Placenta-02.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/2910_The_Placenta-02.jpg/420px-2910_The_Placenta-02.jpg" decoding="async" width="420" height="218" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/2910_The_Placenta-02.jpg/630px-2910_The_Placenta-02.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2d/2910_The_Placenta-02.jpg/840px-2910_The_Placenta-02.jpg 2x" data-file-width="2059" data-file-height="1068" /></a><figcaption>Embryo attached to placenta in amniotic cavity</figcaption></figure> <p>The <a href="/wiki/Primitive_streak" title="Primitive streak">primitive streak</a>, a linear collection of cells formed by the migrating epiblast, appears, and this marks the beginning of <a href="/wiki/Gastrulation" title="Gastrulation">gastrulation</a>, which takes place around the seventeenth day (week 3) after fertilization. The process of gastrulation reorganises the two-layer embryo into a three-layer embryo, and also gives the embryo its specific head-to-tail, and front-to-back orientation, by way of the primitive streak which establishes <a href="/wiki/Bilateral_symmetry" class="mw-redirect" title="Bilateral symmetry">bilateral symmetry</a>. A <a href="/wiki/Primitive_node" title="Primitive node">primitive node</a> (or primitive knot) forms in front of the primitive streak which is the organiser of <a href="/wiki/Neurulation" title="Neurulation">neurulation</a>. A <a href="/wiki/Primitive_pit" class="mw-redirect" title="Primitive pit">primitive pit</a> forms as a depression in the centre of the primitive node which connects to the <a href="/wiki/Notochord" title="Notochord">notochord</a> which lies directly underneath. The node has arisen from epiblasts of the amniotic cavity floor, and it is this node that induces the formation of the <a href="/wiki/Neural_plate" title="Neural plate">neural plate</a> which serves as the basis for the nervous system. </p><p>The neural plate will form opposite the primitive streak from ectodermal tissue which thickens and flattens into the neural plate. The epiblast in that region moves down into the streak at the location of the primitive pit where the process called <a href="/wiki/Ingression_(biology)" title="Ingression (biology)">ingression</a>, which leads to the formation of the mesoderm takes place. This ingression sees the cells from the epiblast move into the primitive streak in an <a href="/wiki/Epithelial-mesenchymal_transition" class="mw-redirect" title="Epithelial-mesenchymal transition">epithelial-mesenchymal transition</a>; epithelial cells become mesenchymal stem cells, <a href="/wiki/Multipotent" class="mw-redirect" title="Multipotent">multipotent</a> <a href="/wiki/Stromal" class="mw-redirect" title="Stromal">stromal</a> cells that can <a href="/wiki/Cellular_differentiation" title="Cellular differentiation">differentiate</a> into various cell types. The hypoblast is pushed out of the way and goes on to form the <a href="/wiki/Amnion" title="Amnion">amnion</a>. The epiblast keeps moving and forms a second layer, the mesoderm. The epiblast has now differentiated into the three <a href="/wiki/Germ_layer" title="Germ layer">germ layers</a> of the embryo, so that the bilaminar disc is now a trilaminar disc, the <a href="/wiki/Gastrula" class="mw-redirect" title="Gastrula">gastrula</a>. </p><p>The three germ layers are the <a href="/wiki/Ectoderm" title="Ectoderm">ectoderm</a>, <a href="/wiki/Mesoderm" title="Mesoderm">mesoderm</a> and <a href="/wiki/Endoderm" title="Endoderm">endoderm</a>, and are formed as three overlapping flat discs. It is from these three layers that all the structures and organs of the body will be derived through the processes of <a href="/wiki/Somitogenesis" title="Somitogenesis">somitogenesis</a>, <a href="/wiki/Histogenesis" title="Histogenesis">histogenesis</a> and <a href="/wiki/Organogenesis" title="Organogenesis">organogenesis</a>.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> The embryonic endoderm is formed by <a href="/wiki/Invagination" title="Invagination">invagination</a> of epiblastic cells that migrate to the hypoblast, while the mesoderm is formed by the cells that develop between the epiblast and endoderm. In general, all germ layers will derive from the epiblast.<sup id="cite_ref-Sadler_11-7" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Smith_15-1" class="reference"><a href="#cite_note-Smith-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> The upper layer of ectoderm will give rise to the outermost layer of skin, central and peripheral <a href="/wiki/Nervous_system" title="Nervous system">nervous systems</a>, <a href="/wiki/Human_eyes" class="mw-redirect" title="Human eyes">eyes</a>, <a href="/wiki/Inner_ear" title="Inner ear">inner ear</a>, and many <a href="/wiki/Connective_tissues" class="mw-redirect" title="Connective tissues">connective tissues</a>.<sup id="cite_ref-D_17-0" class="reference"><a href="#cite_note-D-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> The middle layer of mesoderm will give rise to the heart and the beginning of the <a href="/wiki/Circulatory_system" title="Circulatory system">circulatory system</a> as well as the <a href="/wiki/Bone" title="Bone">bones</a>, <a href="/wiki/Muscles" class="mw-redirect" title="Muscles">muscles</a> and <a href="/wiki/Kidneys" class="mw-redirect" title="Kidneys">kidneys</a>. The inner layer of endoderm will serve as the starting point for the development of the <a href="/wiki/Lungs" class="mw-redirect" title="Lungs">lungs</a>, <a href="/wiki/Intestine" class="mw-redirect" title="Intestine">intestine</a>, <a href="/wiki/Thyroid" title="Thyroid">thyroid</a>, <a href="/wiki/Pancreas" title="Pancreas">pancreas</a> and <a href="/wiki/Urinary_bladder" class="mw-redirect" title="Urinary bladder">bladder</a>. </p><p>Following ingression, a <a href="/wiki/Gastrulation#Overview" title="Gastrulation">blastopore</a> develops where the cells have ingressed, in one side of the embryo and it deepens to become the <a href="/wiki/Archenteron" title="Archenteron">archenteron</a>, the first formative stage of the <a href="/wiki/Gut_(anatomy)" class="mw-redirect" title="Gut (anatomy)">gut</a>. As in all <a href="/wiki/Deuterostome" title="Deuterostome">deuterostomes</a>, the blastopore becomes the <a href="/wiki/Anus" title="Anus">anus</a> whilst the gut tunnels through the embryo to the other side where the opening becomes the mouth. With a functioning digestive tube, gastrulation is now completed and the next stage of <a href="/wiki/Neurulation" title="Neurulation">neurulation</a> can begin. </p> <div class="mw-heading mw-heading2"><h2 id="Neurulation">Neurulation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=8" title="Edit section: Neurulation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Neurulation" title="Neurulation">Neurulation</a></div> <figure class="mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Neural_crest.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/60/Neural_crest.svg/220px-Neural_crest.svg.png" decoding="async" width="220" height="264" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/60/Neural_crest.svg/330px-Neural_crest.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/60/Neural_crest.svg/440px-Neural_crest.svg.png 2x" data-file-width="450" data-file-height="540" /></a><figcaption>Neural plate</figcaption></figure> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Embryonic_Development_CNS.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/15/Embryonic_Development_CNS.png/280px-Embryonic_Development_CNS.png" decoding="async" width="280" height="260" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/1/15/Embryonic_Development_CNS.png 1.5x" data-file-width="350" data-file-height="325" /></a><figcaption>Neural tube development</figcaption></figure> <p>Following gastrulation, the ectoderm gives rise to epithelial and <a href="/wiki/Nervous_tissue" title="Nervous tissue">neural tissue</a>, and the gastrula is now referred to as the <a href="/wiki/Neurula" title="Neurula">neurula</a>. The <a href="/wiki/Neural_plate" title="Neural plate">neural plate</a> that has formed as a thickened plate from the ectoderm, continues to broaden and its ends start to fold upwards as <a href="/wiki/Neural_folds" class="mw-redirect" title="Neural folds">neural folds</a>. <a href="/wiki/Neurulation" title="Neurulation">Neurulation</a> refers to this folding process whereby the neural plate is transformed into the <a href="/wiki/Neural_tube" title="Neural tube">neural tube</a>, and this takes place during the fourth week. They fold, along a shallow <a href="/wiki/Neural_groove" title="Neural groove">neural groove</a> which has formed as a dividing median line in the neural plate. This deepens as the folds continue to gain height, when they will meet and close together at the <a href="/wiki/Neural_crest" title="Neural crest">neural crest</a>. The cells that migrate through the most cranial part of the primitive line form the <a href="/wiki/Paraxial_mesoderm" title="Paraxial mesoderm">paraxial mesoderm</a>, which will give rise to the <a href="/wiki/Somitomeres" class="mw-redirect" title="Somitomeres">somitomeres</a> that in the process of <a href="/wiki/Somitogenesis" title="Somitogenesis">somitogenesis</a> will differentiate into <a href="/wiki/Somite" title="Somite">somites</a> that will form the <a href="/wiki/Sclerotome" class="mw-redirect" title="Sclerotome">sclerotomes</a>, the <a href="/wiki/Somite" title="Somite">syndetomes</a>,<sup id="cite_ref-pmid12705871_18-0" class="reference"><a href="#cite_note-pmid12705871-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> the <a href="/wiki/Myotome" title="Myotome">myotomes</a> and the <a href="/wiki/Somite" title="Somite">dermatomes</a> to form <a href="/wiki/Cartilage" title="Cartilage">cartilage</a> and <a href="/wiki/Bone" title="Bone">bone</a>, <a href="/wiki/Tendon" title="Tendon">tendons</a>, <a href="/wiki/Dermis" title="Dermis">dermis</a> (skin), and <a href="/wiki/Muscle" title="Muscle">muscle</a>. The intermediate mesoderm gives rise to the <a href="/wiki/Genitourinary_system" title="Genitourinary system">urogenital tract</a> and consists of cells that migrate from the middle region of the primitive line. Other cells migrate through the <a href="/wiki/Caudal_(anatomical_term)" class="mw-redirect" title="Caudal (anatomical term)">caudal</a> part of the primitive line and form the lateral mesoderm, and those cells migrating by the most caudal part contribute to the extraembryonic mesoderm.<sup id="cite_ref-Sadler_11-8" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Smith_15-2" class="reference"><a href="#cite_note-Smith-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p><p>The embryonic disc begins flat and round, but eventually elongates to have a wider cephalic part and narrow-shaped caudal end.<sup id="cite_ref-Carlson_10-4" class="reference"><a href="#cite_note-Carlson-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> At the beginning, the primitive line extends in <a href="/wiki/Cephalic" class="mw-redirect" title="Cephalic">cephalic</a> direction and 18 days after fertilization returns caudally until it disappears. In the cephalic portion, the germ layer shows specific differentiation at the beginning of the fourth week, while in the caudal portion it occurs at the end of the fourth week.<sup id="cite_ref-Sadler_11-9" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> Cranial and caudal <a href="/wiki/Neurulation#Folding" title="Neurulation">neuropores</a> become progressively smaller until they close completely (by day 26) forming the <a href="/wiki/Neural_tube" title="Neural tube">neural tube</a>.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading2"><h2 id="Development_of_organs_and_organ_systems">Development of organs and organ systems</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=9" title="Edit section: Development of organs and organ systems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:9-Week_Human_Embryo_from_Ectopic_Pregnancy.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/53/9-Week_Human_Embryo_from_Ectopic_Pregnancy.jpg/220px-9-Week_Human_Embryo_from_Ectopic_Pregnancy.jpg" decoding="async" width="220" height="330" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/53/9-Week_Human_Embryo_from_Ectopic_Pregnancy.jpg/330px-9-Week_Human_Embryo_from_Ectopic_Pregnancy.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/53/9-Week_Human_Embryo_from_Ectopic_Pregnancy.jpg/440px-9-Week_Human_Embryo_from_Ectopic_Pregnancy.jpg 2x" data-file-width="2054" data-file-height="3081" /></a><figcaption>Nine-week-old human embryo from an <a href="/wiki/Ectopic_pregnancy" title="Ectopic pregnancy">ectopic pregnancy</a></figcaption></figure> <p><a href="/wiki/Organogenesis" title="Organogenesis">Organogenesis</a> is the development of the <a href="/wiki/Organ_(anatomy)" class="mw-redirect" title="Organ (anatomy)">organs</a> that begins during the third to eighth week, and continues until birth. Sometimes full development, as in the lungs, continues after birth. Different organs take part in the development of the many <a href="/wiki/Organ_system" title="Organ system">organ systems</a> of the body. </p> <div class="mw-heading mw-heading3"><h3 id="Blood">Blood</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=10" title="Edit section: Blood"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Haematopoietic_stem_cell" class="mw-redirect" title="Haematopoietic stem cell">Haematopoietic stem cells</a> that give rise to all the <a href="/wiki/Blood_cell" title="Blood cell">blood cells</a> develop from the mesoderm. The development of <a href="/wiki/Haematopoiesis" title="Haematopoiesis">blood formation</a> takes place in clusters of blood cells, known as <a href="/wiki/Blood_island" class="mw-redirect" title="Blood island">blood islands</a>, in the <a href="/wiki/Yolk_sac" title="Yolk sac">yolk sac</a>. Blood islands develop outside the embryo, on the umbilical vesicle, allantois, connecting stalk, and chorion, from mesodermal <a href="/wiki/Hemangioblast" title="Hemangioblast">hemangioblasts</a>. </p><p>In the centre of a blood island, hemangioblasts form the haematopoietic stem cells that are the precursor to all types of blood cell. In the periphery of a blood island the hemangioblasts differentiate into <a href="/wiki/Angioblast" title="Angioblast">angioblasts</a>, the precursors to the blood vessels.<sup id="cite_ref-LME_20-0" class="reference"><a href="#cite_note-LME-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Heart_and_circulatory_system">Heart and circulatory system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=11" title="Edit section: Heart and circulatory system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Heart_development" title="Heart development">Heart development</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Vascular_remodelling_in_the_embryo" title="Vascular remodelling in the embryo">Vascular remodelling in the embryo</a></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:2037_Embryonic_Development_of_Heart.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/74/2037_Embryonic_Development_of_Heart.jpg/450px-2037_Embryonic_Development_of_Heart.jpg" decoding="async" width="450" height="388" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/74/2037_Embryonic_Development_of_Heart.jpg/675px-2037_Embryonic_Development_of_Heart.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/74/2037_Embryonic_Development_of_Heart.jpg/900px-2037_Embryonic_Development_of_Heart.jpg 2x" data-file-width="2267" data-file-height="1954" /></a><figcaption></figcaption></figure> <p>The heart is the first functional organ to develop and starts to beat and pump blood at around 22 days.<sup id="cite_ref-Anatomy_&_physiology_21-0" class="reference"><a href="#cite_note-Anatomy_&_physiology-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> Cardiac <a href="/wiki/Myoblast" class="mw-redirect" title="Myoblast">myoblasts</a> and <a href="/wiki/Blood_islands" title="Blood islands">blood islands</a> in the <a href="/wiki/Splanchnopleuric_mesenchyme" title="Splanchnopleuric mesenchyme">splanchnopleuric mesenchyme</a> on each side of the <a href="/wiki/Neural_plate" title="Neural plate">neural plate</a> give rise to the <a href="/wiki/Cardiogenic_region" class="mw-redirect" title="Cardiogenic region">cardiogenic region</a>.<sup id="cite_ref-Sadler_11-10" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page / location: 165">: 165 </span></sup>This is a horseshoe-shaped area near to the head of the embryo. By day 19, following <a href="/wiki/Cell_signalling" class="mw-redirect" title="Cell signalling">cell signalling</a>, two strands begin to form as tubes in this region, as a lumen develops within them. These two <a href="/wiki/Endocardial_tubes" title="Endocardial tubes">endocardial tubes</a> grow and by day 21 have migrated towards each other and fused to form a single primitive heart tube, the <a href="/wiki/Tubular_heart" title="Tubular heart">tubular heart</a>. This is enabled by the folding of the embryo which pushes the tubes into the <a href="/wiki/Thoracic_cavity" title="Thoracic cavity">thoracic cavity</a>.<sup id="cite_ref-Human_Embryology_22-0" class="reference"><a href="#cite_note-Human_Embryology-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> </p><p>Also at the same time that the endocardial tubes are forming, <a href="/wiki/Vasculogenesis" title="Vasculogenesis">vasculogenesis</a> (the development of the circulatory system) has begun. This starts on day 18 with cells in the splanchnopleuric mesoderm differentiating into <a href="/wiki/Angioblast" title="Angioblast">angioblasts</a> that develop into flattened endothelial cells. These join to form small vesicles called angiocysts which join up to form long vessels called angioblastic cords. These cords develop into a pervasive network of plexuses in the formation of the vascular network. This network grows by the additional budding and sprouting of new vessels in the process of <a href="/wiki/Angiogenesis" title="Angiogenesis">angiogenesis</a>.<sup id="cite_ref-Human_Embryology_22-1" class="reference"><a href="#cite_note-Human_Embryology-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> Following vasculogenesis and the development of an early vasculature, a stage of <a href="/wiki/Vascular_remodelling_in_the_embryo" title="Vascular remodelling in the embryo">vascular remodelling</a> takes place. </p><p>The tubular heart quickly forms five distinct regions. From head to tail, these are the <a href="/wiki/Infundibulum_(heart)" title="Infundibulum (heart)">infundibulum</a>, <a href="/wiki/Bulbus_cordis" title="Bulbus cordis">bulbus cordis</a>, <a href="/wiki/Primitive_ventricle" title="Primitive ventricle">primitive ventricle</a>, <a href="/wiki/Primitive_atrium" title="Primitive atrium">primitive atrium</a>, and the <a href="/wiki/Sinus_venosus" title="Sinus venosus">sinus venosus</a>. Initially, all venous blood flows into the sinus venosus, and is propelled from tail to head to the <a href="/wiki/Truncus_arteriosus" title="Truncus arteriosus">truncus arteriosus</a>. This will divide to form the <a href="/wiki/Aorta" title="Aorta">aorta</a> and <a href="/wiki/Pulmonary_artery" title="Pulmonary artery">pulmonary artery</a>; the bulbus cordis will develop into the right (primitive) ventricle; the primitive ventricle will form the left ventricle; the primitive atrium will become the front parts of the left and right atria and their appendages, and the sinus venosus will develop into the posterior part of the right <a href="/wiki/Atrium_(heart)" title="Atrium (heart)">atrium</a>, the <a href="/wiki/Sinoatrial_node" title="Sinoatrial node">sinoatrial node</a> and the <a href="/wiki/Coronary_sinus" title="Coronary sinus">coronary sinus</a>.<sup id="cite_ref-Anatomy_&_physiology_21-1" class="reference"><a href="#cite_note-Anatomy_&_physiology-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>Cardiac looping begins to shape the heart as one of the processes of <a href="/wiki/Morphogenesis" title="Morphogenesis">morphogenesis</a>, and this completes by the end of the fourth week. <a href="/wiki/Programmed_cell_death" title="Programmed cell death">Programmed cell death</a> (<a href="/wiki/Apoptosis" title="Apoptosis">apoptosis</a>) at the joining surfaces enables fusion to take place.<sup id="cite_ref-Human_Embryology_22-2" class="reference"><a href="#cite_note-Human_Embryology-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> In the middle of the fourth week, the sinus venosus receives blood from the three major veins: the <a href="/wiki/Vitelline_vein" class="mw-redirect" title="Vitelline vein">vitelline</a>, the <a href="/wiki/Umbilical_vein" title="Umbilical vein">umbilical</a> and the <a href="/wiki/Common_cardinal_vein" class="mw-redirect" title="Common cardinal vein">common cardinal veins</a>. </p><p>During the first two months of development, the <a href="/wiki/Interatrial_septum" title="Interatrial septum">interatrial septum</a> begins to form. This septum divides the <a href="/wiki/Primitive_atrium" title="Primitive atrium">primitive atrium</a> into a right and a left <a href="/wiki/Atrium_(heart)" title="Atrium (heart)">atrium</a>. Firstly it starts as a crescent-shaped piece of tissue which grows downwards as the <a href="/wiki/Septum_primum" title="Septum primum">septum primum</a>. The crescent shape prevents the complete closure of the atria allowing blood to be shunted from the right to the left atrium through the opening known as the <a href="/wiki/Ostium_primum" class="mw-redirect" title="Ostium primum">ostium primum</a>. This closes with further development of the system but before it does, a second opening (the <a href="/wiki/Ostium_secundum" class="mw-redirect" title="Ostium secundum">ostium secundum</a>) begins to form in the upper atrium enabling the continued shunting of blood.<sup id="cite_ref-Human_Embryology_22-3" class="reference"><a href="#cite_note-Human_Embryology-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> </p><p>A second septum (the <a href="/wiki/Septum_secundum" title="Septum secundum">septum secundum</a>) begins to form to the right of the septum primum. This also leaves a small opening, the <a href="/wiki/Foramen_ovale_(heart)" title="Foramen ovale (heart)">foramen ovale</a> which is continuous with the previous opening of the ostium secundum. The septum primum is reduced to a small flap that acts as the valve of the foramen ovale and this remains until its closure at birth. Between the <a href="/wiki/Ventricle_(heart)" title="Ventricle (heart)">ventricles</a> the <a href="/wiki/Intraventricular_septum" class="mw-redirect" title="Intraventricular septum">septum inferius</a> also forms which develops into the muscular <a href="/wiki/Interventricular_septum" title="Interventricular septum">interventricular septum</a>.<sup id="cite_ref-Human_Embryology_22-4" class="reference"><a href="#cite_note-Human_Embryology-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Digestive_system">Digestive system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=12" title="Edit section: Digestive system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Development_of_the_digestive_system" title="Development of the digestive system">Development of the digestive system</a></div> <p>The digestive system starts to develop from the third week and by the twelfth week, the organs have correctly positioned themselves. </p> <div class="mw-heading mw-heading3"><h3 id="Respiratory_system">Respiratory system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=13" title="Edit section: Respiratory system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Lung#Development" title="Lung">Lung § Development</a></div> <p>The respiratory system develops from the <a href="/wiki/Lung_bud" title="Lung bud">lung bud</a>, which appears in the ventral wall of the foregut about four weeks into development. The lung bud forms the trachea and two lateral growths known as the bronchial buds, which enlarge at the beginning of the fifth week to form the left and right main <a href="/wiki/Bronchus" title="Bronchus">bronchi</a>. These bronchi in turn form secondary (lobar) bronchi; three on the right and two on the left (reflecting the number of lung lobes). Tertiary bronchi form from secondary bronchi. </p><p>While the internal lining of the <a href="/wiki/Larynx" title="Larynx">larynx</a> originates from the <a href="/wiki/Lung_bud" title="Lung bud">lung bud</a>, its cartilages and muscles originate from the fourth and sixth <a href="/wiki/Pharyngeal_arch" title="Pharyngeal arch">pharyngeal arches</a>.<sup id="cite_ref-:0_23-0" class="reference"><a href="#cite_note-:0-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Urinary_system">Urinary system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=14" title="Edit section: Urinary system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="/wiki/Development_of_the_urinary_system" title="Development of the urinary system">Development of the urinary system</a> and <a href="/wiki/Kidney_development" title="Kidney development">Kidney development</a></div> <div class="mw-heading mw-heading4"><h4 id="Kidneys">Kidneys</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=15" title="Edit section: Kidneys"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Three different <a href="/wiki/Kidney" title="Kidney">kidney</a> systems form in the developing embryo: the <a href="/wiki/Pronephros" title="Pronephros">pronephros</a>, the <a href="/wiki/Mesonephros" title="Mesonephros">mesonephros</a> and the <a href="/wiki/Kidney_development#Metanephros" title="Kidney development">metanephros</a>. Only the metanephros develops into the permanent kidney. All three are derived from the <a href="/wiki/Intermediate_mesoderm" title="Intermediate mesoderm">intermediate mesoderm</a>. </p> <div class="mw-heading mw-heading5"><h5 id="Pronephros">Pronephros</h5><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=16" title="Edit section: Pronephros"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Pronephros" title="Pronephros">pronephros</a> derives from the intermediate mesoderm in the cervical region. It is not functional and degenerates before the end of the fourth week. </p> <div class="mw-heading mw-heading5"><h5 id="Mesonephros">Mesonephros</h5><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=17" title="Edit section: Mesonephros"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Mesonephros" title="Mesonephros">mesonephros</a> derives from intermediate mesoderm in the upper thoracic to upper lumbar segments. Excretory tubules are formed and enter the <a href="/wiki/Mesonephric_duct" title="Mesonephric duct">mesonephric duct</a>, which ends in the <a href="/wiki/Cloaca_(embryology)" title="Cloaca (embryology)">cloaca</a>. The mesonephric duct atrophies in females, but participate in <a href="/wiki/Development_of_the_reproductive_system" title="Development of the reproductive system">development of the reproductive system</a> in males. </p> <div class="mw-heading mw-heading5"><h5 id="Metanephros">Metanephros</h5><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=18" title="Edit section: Metanephros"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The metanephros appears in the fifth week of development. An outgrowth of the mesonephric duct, the <a href="/wiki/Ureteric_bud" title="Ureteric bud">ureteric bud</a>, penetrates metanephric tissue to form the primitive <a href="/wiki/Renal_pelvis" title="Renal pelvis">renal pelvis</a>, <a href="/wiki/Renal_calyx" title="Renal calyx">renal calyces</a> and <a href="/wiki/Renal_pyramids" class="mw-redirect" title="Renal pyramids">renal pyramids</a>. The <a href="/wiki/Ureter" title="Ureter">ureter</a> is also formed. </p> <div class="mw-heading mw-heading4"><h4 id="Bladder_and_urethra">Bladder and urethra</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=19" title="Edit section: Bladder and urethra"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Between the fourth and seventh weeks of development, the <a href="/wiki/Urorectal_septum" title="Urorectal septum">urorectal septum</a> divides the <a href="/wiki/Cloaca_(embryology)" title="Cloaca (embryology)">cloaca</a> into the <a href="/wiki/Urogenital_sinus" title="Urogenital sinus">urogenital sinus</a> and the <a href="/wiki/Anal_canal" title="Anal canal">anal canal</a>. The upper part of the urogenital sinus forms the <a href="/wiki/Urinary_bladder" class="mw-redirect" title="Urinary bladder">bladder</a>, while the lower part forms the <a href="/wiki/Urethra" title="Urethra">urethra</a>.<sup id="cite_ref-:0_23-1" class="reference"><a href="#cite_note-:0-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Reproductive_system">Reproductive system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=20" title="Edit section: Reproductive system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Development_of_the_reproductive_system" title="Development of the reproductive system">Development of the reproductive system</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Development_of_the_gonads" title="Development of the gonads">Development of the gonads</a></div> <div class="mw-heading mw-heading3"><h3 id="Integumentary_system">Integumentary system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=21" title="Edit section: Integumentary system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Human_skin_colour" class="mw-redirect" title="Human skin colour">Human skin colour</a></div> <p>The superficial layer of the <a href="/wiki/Human_skin" title="Human skin">skin</a>, the <a href="/wiki/Epidermis" title="Epidermis">epidermis</a>, is derived from the <a href="/wiki/Ectoderm" title="Ectoderm">ectoderm</a>. The deeper layer, the <a href="/wiki/Dermis" title="Dermis">dermis</a>, is derived from <a href="/wiki/Mesenchyme" title="Mesenchyme">mesenchyme</a>. </p><p>The formation of the epidermis begins in the second month of development and it acquires its definitive arrangement at the end of the fourth month. The ectoderm divides to form a flat layer of cells on the surface known as the periderm. Further division forms the individual <a href="/wiki/Epidermis#Layers" title="Epidermis">layers of the epidermis</a>. </p><p>The mesenchyme that will form the dermis is derived from three sources: </p> <ul><li>The mesenchyme that forms the dermis in the limbs and body wall derives from the <a href="/wiki/Lateral_plate_mesoderm" title="Lateral plate mesoderm">lateral plate mesoderm</a></li> <li>The mesenchyme that forms the dermis in the back derives from <a href="/wiki/Paraxial_mesoderm" title="Paraxial mesoderm">paraxial mesoderm</a></li> <li>The mesenchyme that forms the dermis in the face and neck derives from <a href="/wiki/Neural_crest" title="Neural crest">neural crest cells</a><sup id="cite_ref-:0_23-2" class="reference"><a href="#cite_note-:0-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup></li></ul> <div class="mw-heading mw-heading3"><h3 id="Nervous_system">Nervous system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=22" title="Edit section: Nervous system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="/wiki/Development_of_the_nervous_system_in_humans" title="Development of the nervous system in humans">Development of the nervous system in humans</a> and <a href="/wiki/Development_of_the_human_brain" class="mw-redirect" title="Development of the human brain">Development of the human brain</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Human_embryo_8_weeks_4.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/77/Human_embryo_8_weeks_4.JPG/240px-Human_embryo_8_weeks_4.JPG" decoding="async" width="240" height="180" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/77/Human_embryo_8_weeks_4.JPG/360px-Human_embryo_8_weeks_4.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/77/Human_embryo_8_weeks_4.JPG/480px-Human_embryo_8_weeks_4.JPG 2x" data-file-width="960" data-file-height="720" /></a><figcaption>Development of brain in eight-week-old embryo</figcaption></figure> <p>Late in the fourth week, the superior part of the neural tube bends ventrally as the <a href="/wiki/Flexure_(embryology)" title="Flexure (embryology)">cephalic flexure</a> at the level of the future <a href="/wiki/Midbrain" title="Midbrain">midbrain</a>—the <a href="/wiki/Mesencephalon" class="mw-redirect" title="Mesencephalon">mesencephalon</a>.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> Above the mesencephalon is the <a href="/wiki/Prosencephalon" class="mw-redirect" title="Prosencephalon">prosencephalon</a> (future forebrain) and beneath it is the <a href="/wiki/Rhombencephalon" class="mw-redirect" title="Rhombencephalon">rhombencephalon</a> (future hindbrain). </p><p><a href="/wiki/Cranial_neural_crest" title="Cranial neural crest">Cranial neural crest</a> cells migrate to the <a href="/wiki/Pharyngeal_arch" title="Pharyngeal arch">pharyngeal arches</a> as <a href="/wiki/Neural_stem_cell" title="Neural stem cell">neural stem cells</a>, where they develop in the process of <a href="/wiki/Neurogenesis" title="Neurogenesis">neurogenesis</a> into <a href="/wiki/Neuron" title="Neuron">neurons</a>. </p><p>The <a href="/wiki/Optic_vesicle" title="Optic vesicle">optical vesicle</a> (which eventually becomes the <a href="/wiki/Optic_nerve" title="Optic nerve">optic nerve</a>, <a href="/wiki/Retina" title="Retina">retina</a> and <a href="/wiki/Iris_(anatomy)" title="Iris (anatomy)">iris</a>) forms at the basal plate of the prosencephalon. The <a href="/wiki/Alar_plate" title="Alar plate">alar plate</a> of the prosencephalon expands to form the cerebral hemispheres (the telencephalon) whilst its <a href="/wiki/Basal_plate_(neural_tube)" title="Basal plate (neural tube)">basal plate</a> becomes the diencephalon. Finally, the optic vesicle grows to form an optic outgrowth. </p> <div class="mw-heading mw-heading2"><h2 id="Development_of_physical_features">Development of physical features</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=23" title="Edit section: Development of physical features"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Face_and_neck">Face and neck</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=24" title="Edit section: Face and neck"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-Expand_section plainlinks metadata ambox mbox-small-left ambox-content" role="presentation"><tbody><tr><td class="mbox-image"><span typeof="mw:File"><a href="/wiki/File:Wiki_letter_w_cropped.svg" class="mw-file-description"><img alt="[icon]" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/20px-Wiki_letter_w_cropped.svg.png" decoding="async" width="20" height="14" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/30px-Wiki_letter_w_cropped.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/40px-Wiki_letter_w_cropped.svg.png 2x" data-file-width="44" data-file-height="31" /></a></span></td><td class="mbox-text"><div class="mbox-text-span">This section <b>needs expansion</b>. You can help by <a class="external text" href="https://en.wikipedia.org/w/index.php?title=Human_embryonic_development&action=edit&section=">adding to it</a>. <span class="date-container"><i>(<span class="date">November 2017</span>)</i></span></div></td></tr></tbody></table> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Face_and_neck_development_of_the_embryo" class="mw-redirect" title="Face and neck development of the embryo">Face and neck development of the embryo</a></div> <p>From the third to the eighth week the <a href="/wiki/Face_and_neck_development_of_the_embryo" class="mw-redirect" title="Face and neck development of the embryo">face and neck develop</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Ears">Ears</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=25" title="Edit section: Ears"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Ear#Development" title="Ear">Ear § Development</a></div><p>The <a href="/wiki/Inner_ear" title="Inner ear">inner ear</a>, <a href="/wiki/Middle_ear" title="Middle ear">middle ear</a> and <a href="/wiki/Outer_ear" title="Outer ear">outer ear</a> have distinct embryological origins. </p><div class="mw-heading mw-heading4"><h4 id="Inner_ear">Inner ear</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=26" title="Edit section: Inner ear"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>At about 22 days into development, the <a href="/wiki/Ectoderm" title="Ectoderm">ectoderm</a> on each side of the <a href="/wiki/Hindbrain" title="Hindbrain">rhombencephalon</a> thickens to form <a href="/wiki/Otic_placode" title="Otic placode">otic placodes</a>. These placodes <a href="/wiki/Invagination" title="Invagination">invaginate</a> to form <a href="/wiki/Otic_pit" title="Otic pit">otic pits</a>, and then <a href="/wiki/Otic_vesicle" title="Otic vesicle">otic vesicles</a>. The otic vesicles then form ventral and dorsal components. </p><p>The ventral component forms the <a href="/wiki/Saccule" title="Saccule">saccule</a> and the <a href="/wiki/Cochlear_duct" title="Cochlear duct">cochlear duct</a>. In the sixth week of development the cochlear duct emerges and penetrates the surrounding <a href="/wiki/Mesenchyme" title="Mesenchyme">mesenchyme</a>, travelling in a spiral shape until it forms 2.5 turns by the end of the eighth week. The saccule is the remaining part of the ventral component. It remains connected to the cochlear duct via the narrow <a href="/wiki/Ductus_reuniens" title="Ductus reuniens">ductus reuniens</a>. </p><p>The dorsal component forms the <a href="/wiki/Utricle_(ear)" title="Utricle (ear)">utricle</a> and <a href="/wiki/Semicircular_canals" title="Semicircular canals">semicircular canals</a>. </p> <div class="mw-heading mw-heading4"><h4 id="Middle_ear">Middle ear</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=27" title="Edit section: Middle ear"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Pharyngeal_pouch_(embryology)#First_pouch" title="Pharyngeal pouch (embryology)">first pharyngeal pouch</a> lengthens and expands to form the <b>tubotympanic recess</b>. This recess differentiates to form most of the <a href="/wiki/Tympanic_cavity" title="Tympanic cavity">tympanic cavity</a> of the <a href="/wiki/Middle_ear" title="Middle ear">middle ear</a>, and all of the <a href="/wiki/Eustachian_tube" title="Eustachian tube">Eustachian or auditory tube</a>. The narrow auditory tube connects the tympanic cavity to the <a href="/wiki/Pharynx" title="Pharynx">pharynx</a>.<sup id="cite_ref-Larsen2015_25-0" class="reference"><a href="#cite_note-Larsen2015-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/Bone" title="Bone">bones</a> of the middle ear, the <a href="/wiki/Ossicles" title="Ossicles">ossicles</a>, derive from the cartilages of the <a href="/wiki/Pharyngeal_arch" title="Pharyngeal arch">pharyngeal arches</a>. The <a href="/wiki/Malleus" title="Malleus">malleus</a> and <a href="/wiki/Incus" title="Incus">incus</a> derive from the cartilage of the <a href="/wiki/Pharyngeal_arch#First_arch" title="Pharyngeal arch">first pharyngeal arch</a>, whereas the <a href="/wiki/Stapes" title="Stapes">stapes</a> derives from the cartilage of the <a href="/wiki/Pharyngeal_arch#Second_arch" title="Pharyngeal arch">second pharyngeal arch</a>. </p> <div class="mw-heading mw-heading4"><h4 id="Outer_ear">Outer ear</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=28" title="Edit section: Outer ear"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Ear_canal" title="Ear canal">external auditory meatus</a> develops from the dorsal portion of the first <a href="/wiki/Pharyngeal_groove" title="Pharyngeal groove">pharyngeal cleft</a>. Six auricular hillocks, which are mesenchymal proliferations at the dorsal aspects of the first and second pharyngeal arches, form the <a href="/wiki/Auricle_(anatomy)" title="Auricle (anatomy)">auricle</a> of the ear.<sup id="cite_ref-:0_23-3" class="reference"><a href="#cite_note-:0-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Eyes">Eyes</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=29" title="Edit section: Eyes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Eye_development" title="Eye development">Eye development</a></div> <p>The eyes begin to develop from the third week to the tenth week. </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Movements_at_gestational_age_of_9_weeks.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/61/Movements_at_gestational_age_of_9_weeks.gif/220px-Movements_at_gestational_age_of_9_weeks.gif" decoding="async" width="220" height="167" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/6/61/Movements_at_gestational_age_of_9_weeks.gif 1.5x" data-file-width="267" data-file-height="203" /></a><figcaption>Movements of embryo at nine weeks gestational age</figcaption></figure> <div class="mw-heading mw-heading3"><h3 id="Limbs">Limbs</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=30" title="Edit section: Limbs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1251242444"><table class="box-Expand_section plainlinks metadata ambox mbox-small-left ambox-content" role="presentation"><tbody><tr><td class="mbox-image"><span typeof="mw:File"><a href="/wiki/File:Wiki_letter_w_cropped.svg" class="mw-file-description"><img alt="[icon]" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/20px-Wiki_letter_w_cropped.svg.png" decoding="async" width="20" height="14" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/30px-Wiki_letter_w_cropped.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/40px-Wiki_letter_w_cropped.svg.png 2x" data-file-width="44" data-file-height="31" /></a></span></td><td class="mbox-text"><div class="mbox-text-span">This section <b>needs expansion</b>. You can help by <a class="external text" href="https://en.wikipedia.org/w/index.php?title=Human_embryonic_development&action=edit&section=">adding to it</a>. <span class="date-container"><i>(<span class="date">November 2017</span>)</i></span></div></td></tr></tbody></table> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="/wiki/Limb_development" title="Limb development">Limb development</a> and <a href="/wiki/Limb_bud" title="Limb bud">Limb bud</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Zone_of_polarizing_activity" title="Zone of polarizing activity">Zone of polarizing activity</a> and <a href="/wiki/Polymelia" title="Polymelia">polymelia</a></div> <p>At the end of the fourth week <a href="/wiki/Limb_development" title="Limb development">limb development</a> begins. <a href="/wiki/Limb_bud" title="Limb bud">Limb buds</a> appear on the ventrolateral aspect of the body. They consist of an outer layer of <a href="/wiki/Ectoderm" title="Ectoderm">ectoderm</a> and an inner part consisting of <a href="/wiki/Mesenchyme" title="Mesenchyme">mesenchyme</a> which is derived from the parietal layer of <a href="/wiki/Lateral_plate_mesoderm" title="Lateral plate mesoderm">lateral plate mesoderm</a>. Ectodermal cells at the distal end of the buds form the <a href="/wiki/Apical_ectodermal_ridge" title="Apical ectodermal ridge">apical ectodermal ridge</a>, which creates an area of rapidly proliferating mesenchymal cells known as the <a href="/wiki/Progress_zone" title="Progress zone">progress zone</a>. <a href="/wiki/Cartilage" title="Cartilage">Cartilage</a> (some of which ultimately becomes <a href="/wiki/Bone" title="Bone">bone</a>) and muscle develop from the mesenchyme.<sup id="cite_ref-:0_23-4" class="reference"><a href="#cite_note-:0-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Clinical_significance">Clinical significance</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=31" title="Edit section: Clinical significance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Prenatal_testing" title="Prenatal testing">Prenatal testing</a> and <a href="/wiki/Environmental_toxicants_and_fetal_development" title="Environmental toxicants and fetal development">Environmental toxicants and fetal development</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Obstetric_ultrasonography" title="Obstetric ultrasonography">Obstetric ultrasonography</a></div> <p>Toxic exposures in the embryonic period can be the cause of major <a href="/wiki/Congenital_malformation" class="mw-redirect" title="Congenital malformation">congenital malformations</a>, since the precursors of the major organ systems are now developing. </p><p>Each cell of the preimplantation embryo has the potential to form all of the <a href="/wiki/Cellular_differentiation" title="Cellular differentiation">different cell types</a> in the developing embryo. This <a href="/wiki/Cell_potency" title="Cell potency">cell potency</a> means that some cells can be removed from the preimplantation embryo and the remaining cells will compensate for their absence. This has allowed the development of a technique known as <a href="/wiki/Preimplantation_genetic_diagnosis" title="Preimplantation genetic diagnosis">preimplantation genetic diagnosis</a>, whereby a small number of cells from the preimplantation embryo created by <a href="/wiki/In_vitro_fertilisation" title="In vitro fertilisation">IVF</a>, can be removed by <a href="/wiki/Biopsy" title="Biopsy">biopsy</a> and subjected to genetic diagnosis. This allows embryos that are not affected by defined genetic diseases to be selected and then transferred to the mother's <a href="/wiki/Uterus" title="Uterus">uterus</a>. </p><p><a href="/wiki/Sacrococcygeal_teratoma" title="Sacrococcygeal teratoma">Sacrococcygeal teratomas</a>, tumours formed from different types of tissue, that can form, are thought to be related to primitive streak remnants, which ordinarily disappear.<sup id="cite_ref-Carlson_10-5" class="reference"><a href="#cite_note-Carlson-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Sadler_11-11" class="reference"><a href="#cite_note-Sadler-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Larsen_13-1" class="reference"><a href="#cite_note-Larsen-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/First_arch_syndrome" title="First arch syndrome">First arch syndromes</a> are <a href="/wiki/Congenital_disorder" class="mw-redirect" title="Congenital disorder">congenital disorders</a> of facial deformities, caused by the failure of neural crest cells to migrate to the first pharyngeal arch. </p><p><a href="/wiki/Spina_bifida" title="Spina bifida">Spina bifida</a> a <a href="/wiki/Congenital_disorder" class="mw-redirect" title="Congenital disorder">congenital disorder</a> is the result of the incomplete closure of the neural tube. </p><p><a href="/wiki/Vertically_transmitted_infection" title="Vertically transmitted infection">Vertically transmitted infections</a> can be passed from the mother to the unborn child at any stage of its <a href="/wiki/Prenatal_development" title="Prenatal development">development</a>. </p><p><a href="/wiki/Hypoxia_(medical)" class="mw-redirect" title="Hypoxia (medical)">Hypoxia</a> a condition of inadequate oxygen supply can be a serious consequence of a <a href="/wiki/Preterm_birth" title="Preterm birth">preterm</a> or premature birth. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=32" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col"> <ul><li><a href="/wiki/Embryo_loss" title="Embryo loss">Embryo loss</a></li> <li><a href="/wiki/Aorta-gonad-mesonephros" title="Aorta-gonad-mesonephros">Aorta-gonad-mesonephros</a></li> <li><a href="/wiki/CDX2" class="mw-redirect" title="CDX2">CDX2</a></li> <li><a href="/wiki/Developmental_biology" title="Developmental biology">Developmental biology</a></li> <li><a href="/wiki/Drosophila_embryogenesis" title="Drosophila embryogenesis">Drosophila embryogenesis</a></li> <li><a href="/wiki/Embryomics" title="Embryomics">Embryomics</a></li> <li><a href="/wiki/Human_tooth_development" title="Human tooth development">Human tooth development</a></li> <li><a href="/wiki/List_of_human_cell_types_derived_from_the_germ_layers" title="List of human cell types derived from the germ layers">List of human cell types derived from the germ layers</a></li> <li><a href="/wiki/Potential_person" title="Potential person">Potential person</a></li> <li><a href="/wiki/Recapitulation_theory" title="Recapitulation theory">Recapitulation theory</a></li> <li><a href="/wiki/The_Human_Embryo" title="The Human Embryo">The Human Embryo</a></li> <li><a href="/wiki/Timeline_of_human_prenatal_development" title="Timeline of human prenatal development">Timeline of human prenatal development</a></li></ul> </div> <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=Human_embryonic_development&action=edit&section=33" 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:Didactic_model_of_a_human_embryonic_development_01.jpg" class="mw-file-description" title="Representing different stages of embryogenesis"><img alt="Representing different stages of embryogenesis" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/76/Didactic_model_of_a_human_embryonic_development_01.jpg/120px-Didactic_model_of_a_human_embryonic_development_01.jpg" decoding="async" width="120" height="80" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/76/Didactic_model_of_a_human_embryonic_development_01.jpg/180px-Didactic_model_of_a_human_embryonic_development_01.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/76/Didactic_model_of_a_human_embryonic_development_01.jpg/240px-Didactic_model_of_a_human_embryonic_development_01.jpg 2x" data-file-width="3872" data-file-height="2592" /></a></span></div> <div class="gallerytext">Representing different stages of embryogenesis</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Didactic_model_of_a_human_embryonic_development_05.jpg" class="mw-file-description" title="Early stage of the gastrulation process"><img alt="Early stage of the gastrulation process" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Didactic_model_of_a_human_embryonic_development_05.jpg/120px-Didactic_model_of_a_human_embryonic_development_05.jpg" decoding="async" width="120" height="80" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Didactic_model_of_a_human_embryonic_development_05.jpg/180px-Didactic_model_of_a_human_embryonic_development_05.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Didactic_model_of_a_human_embryonic_development_05.jpg/240px-Didactic_model_of_a_human_embryonic_development_05.jpg 2x" data-file-width="3872" data-file-height="2592" /></a></span></div> <div class="gallerytext">Early stage of the gastrulation process</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Didactic_model_of_a_human_embryonic_development_03.jpg" class="mw-file-description" title="Phase of the gastrulation process"><img alt="Phase of the gastrulation process" src="//upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Didactic_model_of_a_human_embryonic_development_03.jpg/120px-Didactic_model_of_a_human_embryonic_development_03.jpg" decoding="async" width="120" height="80" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Didactic_model_of_a_human_embryonic_development_03.jpg/180px-Didactic_model_of_a_human_embryonic_development_03.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Didactic_model_of_a_human_embryonic_development_03.jpg/240px-Didactic_model_of_a_human_embryonic_development_03.jpg 2x" data-file-width="3791" data-file-height="2538" /></a></span></div> <div class="gallerytext">Phase of the gastrulation process</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Didactic_model_of_a_human_embryonic_development_04.jpg" class="mw-file-description" title="Top of the form of the embryo"><img alt="Top of the form of the embryo" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e3/Didactic_model_of_a_human_embryonic_development_04.jpg/120px-Didactic_model_of_a_human_embryonic_development_04.jpg" decoding="async" width="120" height="80" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e3/Didactic_model_of_a_human_embryonic_development_04.jpg/180px-Didactic_model_of_a_human_embryonic_development_04.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e3/Didactic_model_of_a_human_embryonic_development_04.jpg/240px-Didactic_model_of_a_human_embryonic_development_04.jpg 2x" data-file-width="3872" data-file-height="2592" /></a></span></div> <div class="gallerytext">Top of the form of the embryo</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Didactic_model_of_a_human_embryonic_development_02.jpg" class="mw-file-description" title="Establishment of embryo medium"><img alt="Establishment of embryo medium" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Didactic_model_of_a_human_embryonic_development_02.jpg/120px-Didactic_model_of_a_human_embryonic_development_02.jpg" decoding="async" width="120" height="80" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Didactic_model_of_a_human_embryonic_development_02.jpg/180px-Didactic_model_of_a_human_embryonic_development_02.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Didactic_model_of_a_human_embryonic_development_02.jpg/240px-Didactic_model_of_a_human_embryonic_development_02.jpg 2x" data-file-width="3767" data-file-height="2522" /></a></span></div> <div class="gallerytext">Establishment of embryo medium</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Sobo_1909_621.png" class="mw-file-description" title="Spinal cord at five weeks"><img alt="Spinal cord at five weeks" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6e/Sobo_1909_621.png/120px-Sobo_1909_621.png" decoding="async" width="120" height="84" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6e/Sobo_1909_621.png/180px-Sobo_1909_621.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6e/Sobo_1909_621.png/240px-Sobo_1909_621.png 2x" data-file-width="2344" data-file-height="1644" /></a></span></div> <div class="gallerytext">Spinal cord at five weeks</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Gray947.png" class="mw-file-description" title="Head and neck at 32 days"><img alt="Head and neck at 32 days" src="//upload.wikimedia.org/wikipedia/commons/thumb/3/38/Gray947.png/120px-Gray947.png" decoding="async" width="120" height="80" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/38/Gray947.png/180px-Gray947.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/38/Gray947.png/240px-Gray947.png 2x" data-file-width="532" data-file-height="353" /></a></span></div> <div class="gallerytext">Head and neck at 32 days</div> </li> </ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=34" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></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="http://medical-dictionary.thefreedictionary.com/germinal+stage">"germinal stage"</a>. <i>Mosby's Medical Dictionary, 8th edition</i>. Elsevier<span class="reference-accessdate">. Retrieved <span class="nowrap">6 October</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Mosby%27s+Medical+Dictionary%2C+8th+edition.&rft.atitle=germinal+stage&rft_id=http%3A%2F%2Fmedical-dictionary.thefreedictionary.com%2Fgerminal%2Bstage&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Marlow-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-Marlow_2-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMarlow2020" class="citation book cs1">Marlow, Florence L (2020). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=JX3nDwAAQBAJ&pg=PA124"><i>Maternal Effect Genes in Development</i></a>. Academic Press. p. 124. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0128152218" title="Special:BookSources/978-0128152218"><bdi>978-0128152218</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Maternal+Effect+Genes+in+Development&rft.pages=124&rft.pub=Academic+Press&rft.date=2020&rft.isbn=978-0128152218&rft.aulast=Marlow&rft.aufirst=Florence+L&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DJX3nDwAAQBAJ%26pg%3DPA124&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Singh-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-Singh_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Singh_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSingh2013" class="citation book cs1">Singh, Vishram (2013). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=ABBtAwAAQBAJ&pg=PA35"><i>Textbook of Clinical Embryology – E-book</i></a>. Elsevier Health Sciences. p. 35. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-8131236208" title="Special:BookSources/978-8131236208"><bdi>978-8131236208</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Textbook+of+Clinical+Embryology+%E2%80%93+E-book&rft.pages=35&rft.pub=Elsevier+Health+Sciences&rft.date=2013&rft.isbn=978-8131236208&rft.aulast=Singh&rft.aufirst=Vishram&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DABBtAwAAQBAJ%26pg%3DPA35&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Standring-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-Standring_4-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStandring2015" class="citation book cs1">Standring, Susan (2015). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=b7FVCgAAQBAJ&pg=PA163"><i>Gray's Anatomy E-Book: The Anatomical Basis of Clinical Practice</i></a>. Elsevier Health Sciences. p. 163. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0702068515" title="Special:BookSources/978-0702068515"><bdi>978-0702068515</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Gray%27s+Anatomy+E-Book%3A+The+Anatomical+Basis+of+Clinical+Practice&rft.pages=163&rft.pub=Elsevier+Health+Sciences&rft.date=2015&rft.isbn=978-0702068515&rft.aulast=Standring&rft.aufirst=Susan&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Db7FVCgAAQBAJ%26pg%3DPA163&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Cambridge_University_Press-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Cambridge_University_Press_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Cambridge_University_Press_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFForgács,_G.Newman,_Stuart_A.2005" class="citation book cs1">Forgács, G.; Newman, Stuart A. (2005). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=rUyVWQhk7CkC&pg=PA27">"Cleavage and blastula formation"</a>. <i>Biological physics of the developing embryo</i>. Cambridge University Press. p. 27. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-521-78337-8" title="Special:BookSources/978-0-521-78337-8"><bdi>978-0-521-78337-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Cleavage+and+blastula+formation&rft.btitle=Biological+physics+of+the+developing+embryo&rft.pages=27&rft.pub=Cambridge+University+Press&rft.date=2005&rft.isbn=978-0-521-78337-8&rft.au=Forg%C3%A1cs%2C+G.&rft.au=Newman%2C+Stuart+A.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DrUyVWQhk7CkC%26pg%3DPA27&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Standring2-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-Standring2_6-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStandring2015" class="citation book cs1">Standring, Susan (2015). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=b7FVCgAAQBAJ&pg=PA165"><i>Gray's Anatomy E-Book: The Anatomical Basis of Clinical Practice</i></a>. Elsevier Health Sciences. p. 166. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0702068515" title="Special:BookSources/978-0702068515"><bdi>978-0702068515</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Gray%27s+Anatomy+E-Book%3A+The+Anatomical+Basis+of+Clinical+Practice&rft.pages=166&rft.pub=Elsevier+Health+Sciences&rft.date=2015&rft.isbn=978-0702068515&rft.aulast=Standring&rft.aufirst=Susan&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Db7FVCgAAQBAJ%26pg%3DPA165&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-BrisonSturmey2014-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-BrisonSturmey2014_7-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrisonSturmeyLeese2014" class="citation journal cs1">Brison, D. R.; Sturmey, R. G.; Leese, H. J. 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World Scientific. p. 217. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-981-283-513-0" title="Special:BookSources/978-981-283-513-0"><bdi>978-981-283-513-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=How+New+Humans+Are+Made%3A+Cells+and+Embryos%2C+Twins+and+Chimeras%2C+Left+and+Right%2C+Mind%2FSelf%2FSoul%2C+Sex%2C+and+Schizophrenia&rft.pages=217&rft.pub=World+Scientific&rft.date=2009&rft.isbn=978-981-283-513-0&rft.au=Boklage%2C+Charles+E.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dj7GfgRIgP9YC%26pg%3DPT233&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-opentext-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-opentext_9-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://opentextbc.ca/anatomyandphysiology/chapter/28-2-embryonic-development/">"28.2 Embryonic Development – Anatomy and Physiology"</a>. <i>opentextbc.ca</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=opentextbc.ca&rft.atitle=28.2+Embryonic+Development+%E2%80%93+Anatomy+and+Physiology&rft_id=https%3A%2F%2Fopentextbc.ca%2Fanatomyandphysiology%2Fchapter%2F28-2-embryonic-development%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Carlson-10"><span class="mw-cite-backlink">^ <a href="#cite_ref-Carlson_10-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Carlson_10-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Carlson_10-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Carlson_10-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Carlson_10-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Carlson_10-5"><sup><i><b>f</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCarlson1999" class="citation book cs1">Carlson, Bruce M. 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Mosby, Inc. pp. <span class="nowrap">62–</span>68. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-8151-1458-3" title="Special:BookSources/0-8151-1458-3"><bdi>0-8151-1458-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Chapter+4%3A+Formation+of+germ+layers+and+initial+derivatives&rft.btitle=Human+Embryology+%26+Developmental+Biology&rft.pages=%3Cspan+class%3D%22nowrap%22%3E62-%3C%2Fspan%3E68&rft.pub=Mosby%2C+Inc.&rft.date=1999&rft.isbn=0-8151-1458-3&rft.aulast=Carlson&rft.aufirst=Bruce+M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Sadler-11"><span class="mw-cite-backlink">^ <a href="#cite_ref-Sadler_11-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Sadler_11-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Sadler_11-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Sadler_11-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Sadler_11-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Sadler_11-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Sadler_11-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-Sadler_11-7"><sup><i><b>h</b></i></sup></a> <a href="#cite_ref-Sadler_11-8"><sup><i><b>i</b></i></sup></a> <a href="#cite_ref-Sadler_11-9"><sup><i><b>j</b></i></sup></a> <a href="#cite_ref-Sadler_11-10"><sup><i><b>k</b></i></sup></a> <a href="#cite_ref-Sadler_11-11"><sup><i><b>l</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSadlerLangman2012" class="citation book cs1">Sadler, T.W.; Langman, Jan (2012) [1st. 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Lippincott Williams & Wilkins, Wolters Kluwer. pp. <span class="nowrap">29–</span>42. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-84-15419-83-9" title="Special:BookSources/978-84-15419-83-9"><bdi>978-84-15419-83-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Chapter+3%3A+Primera+semana+del+desarrollo%3A+de+la+ovulaci%C3%B3n+a+la+implantaci%C3%B3n&rft.btitle=Langman%2C+Embriolog%C3%ADa+m%C3%A9dica&rft.pages=%3Cspan+class%3D%22nowrap%22%3E29-%3C%2Fspan%3E42&rft.pub=Lippincott+Williams+%26+Wilkins%2C+Wolters+Kluwer&rft.date=2012&rft.isbn=978-84-15419-83-9&rft.aulast=Sadler&rft.aufirst=T.W.&rft.au=Langman%2C+Jan&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Moore-12"><span class="mw-cite-backlink">^ <a href="#cite_ref-Moore_12-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Moore_12-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMoorePersaud2003" class="citation book cs1">Moore, Keith L.; Persaud, V.N. (2003) [1t. Pub. 1996]. "Chapter 3: Formation of the bilaminar embryonic disc: second week". <i>The Developing Human, Clinically Oriented Embryology</i>. W B Saunders Co. pp. <span class="nowrap">47–</span>51. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-7216-9412-8" title="Special:BookSources/0-7216-9412-8"><bdi>0-7216-9412-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Chapter+3%3A+Formation+of+the+bilaminar+embryonic+disc%3A+second+week&rft.btitle=The+Developing+Human%2C+Clinically+Oriented+Embryology&rft.pages=%3Cspan+class%3D%22nowrap%22%3E47-%3C%2Fspan%3E51&rft.pub=W+B+Saunders+Co&rft.date=2003&rft.isbn=0-7216-9412-8&rft.aulast=Moore&rft.aufirst=Keith+L.&rft.au=Persaud%2C+V.N.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Larsen-13"><span class="mw-cite-backlink">^ <a href="#cite_ref-Larsen_13-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Larsen_13-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLarsenShermanPotterScott2001" class="citation book cs1">Larsen, William J.; Sherman, Lawrence S.; Potter, S. Steven; Scott, William J. (2001) [1t. Pub. 1998]. "Chapter 2: Bilaminar embryonic disc development and establishment of the uteroplacental circulation". <i>Human Embryology</i>. Churchill Livingstone. pp. <span class="nowrap">37–</span>45. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-443-06583-7" title="Special:BookSources/0-443-06583-7"><bdi>0-443-06583-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Chapter+2%3A+Bilaminar+embryonic+disc+development+and+establishment+of+the+uteroplacental+circulation&rft.btitle=Human+Embryology&rft.pages=%3Cspan+class%3D%22nowrap%22%3E37-%3C%2Fspan%3E45&rft.pub=Churchill+Livingstone.&rft.date=2001&rft.isbn=0-443-06583-7&rft.aulast=Larsen&rft.aufirst=William+J.&rft.au=Sherman%2C+Lawrence+S.&rft.au=Potter%2C+S.+Steven&rft.au=Scott%2C+William+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCampbellBrad_WilliamsonRobin_J._Heyden2006" class="citation book cs1">Campbell, Neil A.; Brad Williamson; Robin J. 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Boston: Pearson Prentice Hall. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-13-250882-6" title="Special:BookSources/0-13-250882-6"><bdi>0-13-250882-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Biology%3A+Exploring+Life&rft.place=Boston&rft.pub=Pearson+Prentice+Hall&rft.date=2006&rft.isbn=0-13-250882-6&rft.aulast=Campbell&rft.aufirst=Neil+A.&rft.au=Brad+Williamson&rft.au=Robin+J.+Heyden&rft_id=http%3A%2F%2Fwww.phschool.com%2Fel_marketing.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Smith-15"><span class="mw-cite-backlink">^ <a href="#cite_ref-Smith_15-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Smith_15-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Smith_15-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSmith_AgredaFerrés_TorresMontesinos_Castro-Girona1992" class="citation book cs1">Smith Agreda, Víctor; Ferrés Torres, Elvira; Montesinos Castro-Girona, Manuel (1992). 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Thieme. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-3-13-142081-7" title="Special:BookSources/978-3-13-142081-7"><bdi>978-3-13-142081-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Thieme+Atlas+of+Anatomy%3A+General+Anatomy+and+Musculoskeletal+System&rft.pub=Thieme&rft.date=2006&rft.isbn=978-3-13-142081-7&rft.aulast=Sch%C3%BCnke&rft.aufirst=Michael&rft.au=Ross%2C+Lawrence+M.&rft.au=Schulte%2C+Erik&rft.au=Schumacher%2C+Udo&rft.au=Lamperti%2C+Edward+D.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DNK9TgTaGt6UC%26pg%3DPA6&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-D-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-D_17-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.mayoclinic.com/health/prenatal-care/PR00112/NSECTIONGROUP=2">"Pregnancy week by week"</a><span class="reference-accessdate">. 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Elsevier. p. 87. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-443-06583-7" title="Special:BookSources/0-443-06583-7"><bdi>0-443-06583-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Human+Embryology&rft.pages=87&rft.edition=3rd&rft.pub=Elsevier&rft.date=2001&rft.isbn=0-443-06583-7&rft.aulast=Larsen&rft.aufirst=W+J&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-LME-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-LME_20-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSadler2010" class="citation book cs1">Sadler, T.W. (2010). <i>Langman's Medical Embryology</i> (11th ed.). Baltimore: Lippincott Williams &Wilkins. pp. <span class="nowrap">79–</span>81. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780781790697" title="Special:BookSources/9780781790697"><bdi>9780781790697</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Langman%27s+Medical+Embryology&rft.place=Baltimore&rft.pages=%3Cspan+class%3D%22nowrap%22%3E79-%3C%2Fspan%3E81&rft.edition=11th&rft.pub=Lippincott+Williams+%26Wilkins&rft.date=2010&rft.isbn=9780781790697&rft.aulast=Sadler&rft.aufirst=T.W.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Anatomy_&_physiology-21"><span class="mw-cite-backlink">^ <a href="#cite_ref-Anatomy_&_physiology_21-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Anatomy_&_physiology_21-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBetts2013" class="citation book cs1">Betts, J. Gordon (2013). <a rel="nofollow" class="external text" href="http://cnx.org/content/m46676/latest/?collection=col11496/latest"><i>Anatomy & physiology</i></a>. pp. <span class="nowrap">787–</span>846. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1938168130" title="Special:BookSources/978-1938168130"><bdi>978-1938168130</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Anatomy+%26+physiology&rft.pages=%3Cspan+class%3D%22nowrap%22%3E787-%3C%2Fspan%3E846&rft.date=2013&rft.isbn=978-1938168130&rft.aulast=Betts&rft.aufirst=J.+Gordon&rft_id=http%3A%2F%2Fcnx.org%2Fcontent%2Fm46676%2Flatest%2F%3Fcollection%3Dcol11496%2Flatest&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Human_Embryology-22"><span class="mw-cite-backlink">^ <a href="#cite_ref-Human_Embryology_22-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Human_Embryology_22-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Human_Embryology_22-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Human_Embryology_22-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Human_Embryology_22-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLarsen2001" class="citation book cs1">Larsen, W J (2001). <i>Human Embryology</i> (3rd ed.). Elsevier. pp. <span class="nowrap">170–</span>190. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-443-06583-7" title="Special:BookSources/0-443-06583-7"><bdi>0-443-06583-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Human+Embryology&rft.pages=%3Cspan+class%3D%22nowrap%22%3E170-%3C%2Fspan%3E190&rft.edition=3rd&rft.pub=Elsevier&rft.date=2001&rft.isbn=0-443-06583-7&rft.aulast=Larsen&rft.aufirst=W+J&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-:0-23"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_23-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_23-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:0_23-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-:0_23-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-:0_23-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSadler2012" class="citation book cs1">Sadler, Thomas W. (2012). <i>Langman's medical embryology</i>. Langman, Jan. (12th ed.). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781451113426" title="Special:BookSources/9781451113426"><bdi>9781451113426</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/732776409">732776409</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Langman%27s+medical+embryology.&rft.place=Philadelphia&rft.edition=12th&rft.pub=Wolters+Kluwer+Health%2FLippincott+Williams+%26+Wilkins&rft.date=2012&rft_id=info%3Aoclcnum%2F732776409&rft.isbn=9781451113426&rft.aulast=Sadler&rft.aufirst=Thomas+W.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFZhouSongMing2023" class="citation journal cs1">Zhou, Yi; Song, Hongjun; Ming, Guo-Li (2023-07-28). <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/37507490">"Genetics of human brain development"</a>. <i>Nature Reviews. Genetics</i>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fs41576-023-00626-5">10.1038/s41576-023-00626-5</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1471-0064">1471-0064</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10926850">10926850</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/37507490">37507490</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature+Reviews.+Genetics&rft.atitle=Genetics+of+human+brain+development&rft.date=2023-07-28&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC10926850%23id-name%3DPMC&rft.issn=1471-0064&rft_id=info%3Apmid%2F37507490&rft_id=info%3Adoi%2F10.1038%2Fs41576-023-00626-5&rft.aulast=Zhou&rft.aufirst=Yi&rft.au=Song%2C+Hongjun&rft.au=Ming%2C+Guo-Li&rft_id=https%3A%2F%2Fpubmed.ncbi.nlm.nih.gov%2F37507490&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> <li id="cite_note-Larsen2015-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-Larsen2015_25-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><i>Larsen's human embryology</i> (5. ed.). Philadelphia, Pa: Elsevier, Churchill Livingstone. 2015. p. 485. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781455706846" title="Special:BookSources/9781455706846"><bdi>9781455706846</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Larsen%27s+human+embryology&rft.place=Philadelphia%2C+Pa&rft.pages=485&rft.edition=5.&rft.pub=Elsevier%2C+Churchill+Livingstone&rft.date=2015&rft.isbn=9781455706846&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHuman+embryonic+development" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Human_embryonic_development&action=edit&section=35" title="Edit section: External links"><span>edit</span></a><span 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td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Human_embryonic_development_in_the_first_three_weeks166" 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" style="text-align: center;"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Embryology" title="Template:Embryology"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Embryology" title="Template talk:Embryology"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Embryology" title="Special:EditPage/Template:Embryology"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Human_embryonic_development_in_the_first_three_weeks166" style="font-size:114%;margin:0 4em"><a class="mw-selflink selflink">Human embryonic development</a> in the first three weeks</div></th></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Week 1</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Human_fertilization" title="Human fertilization">Fertilization</a></li> <li><a href="/wiki/Oocyte_activation" title="Oocyte activation">Oocyte activation</a></li> <li><a href="/wiki/Zygote" title="Zygote">Zygote</a></li> <li><a href="/wiki/Cleavage_(embryo)" title="Cleavage (embryo)">Cleavage</a></li> <li><a href="/wiki/Blastomere" title="Blastomere">Blastomere</a></li> <li><a href="/wiki/Morula" class="mw-redirect" title="Morula">Morula</a></li> <li><a href="/wiki/Cavitation_(embryology)" title="Cavitation (embryology)">Cavitation</a></li> <li><a href="/wiki/Blastocoel" title="Blastocoel">Blastocoel</a></li> <li><a href="/wiki/Blastocyst" title="Blastocyst">Blastocyst</a></li> <li><a href="/wiki/Inner_cell_mass" title="Inner cell mass">Inner cell mass</a></li> <li><a href="/wiki/Trophoblast" title="Trophoblast">Trophoblast</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Week 2 <br />(<a href="/wiki/Bilaminar_embryonic_disc" title="Bilaminar embryonic disc">Bilaminar</a>)</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Hypoblast" title="Hypoblast">Hypoblast</a></li> <li><a href="/wiki/Epiblast" title="Epiblast">Epiblast</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Week 3 <br />(<a href="/wiki/Trilaminar_blastocyst" class="mw-redirect" title="Trilaminar blastocyst">Trilaminar</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%;text-align: center;"><a href="/wiki/Germ_layer" title="Germ layer">Germ layers</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/Archenteron" title="Archenteron">Archenteron</a>/<a href="/wiki/Primitive_streak" title="Primitive streak">Primitive streak</a> <ul><li><a href="/wiki/Primitive_pit" class="mw-redirect" title="Primitive pit">Primitive pit</a></li> <li><a href="/wiki/Primitive_node" title="Primitive node">Primitive node</a>/<a href="/wiki/Blastopore" class="mw-redirect" title="Blastopore">Blastopore</a></li> <li><a href="/wiki/Primitive_groove" class="mw-redirect" title="Primitive groove">Primitive groove</a></li></ul></li> <li><a href="/wiki/Gastrulation" title="Gastrulation">Gastrula</a> <ul><li><a href="/wiki/Gastrulation" title="Gastrulation">Gastrulation</a></li></ul></li> <li><a href="/wiki/Regional_specification" class="mw-redirect" title="Regional specification">Regional specification</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Ectoderm" title="Ectoderm">Ectoderm</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/Surface_ectoderm" title="Surface ectoderm">Surface ectoderm</a></li> <li><a href="/wiki/Neuroectoderm" title="Neuroectoderm">Neuroectoderm</a></li> <li><a href="/wiki/Somatopleuric_mesenchyme" title="Somatopleuric mesenchyme">Somatopleuric mesenchyme</a></li> <li><a href="/wiki/Neurulation" title="Neurulation">Neurulation</a></li> <li><a href="/wiki/Neural_crest" title="Neural crest">Neural crest</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Endoderm" title="Endoderm">Endoderm</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/Splanchnopleuric_mesenchyme" title="Splanchnopleuric mesenchyme">Splanchnopleuric mesenchyme</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Mesoderm" title="Mesoderm">Mesoderm</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/Axial_mesoderm" title="Axial mesoderm">Axial mesoderm</a></li> <li><a href="/wiki/Paraxial_mesoderm" title="Paraxial mesoderm">Paraxial</a> <ul><li><a href="/wiki/Somite" title="Somite">Somite</a></li> <li><a href="/wiki/Somitomere" title="Somitomere">Somitomere</a></li></ul></li> <li><a href="/wiki/Intermediate_mesoderm" title="Intermediate mesoderm">Intermediate</a></li> <li><a href="/wiki/Lateral_plate_mesoderm" title="Lateral plate mesoderm">Lateral plate</a> <ul><li><a href="/wiki/Intraembryonic_coelom" title="Intraembryonic coelom">Intraembryonic coelom</a></li> <li><a href="/wiki/Splanchnopleuric_mesenchyme" title="Splanchnopleuric mesenchyme">Splanchnopleuric mesenchyme</a></li> <li><a href="/wiki/Somatopleuric_mesenchyme" title="Somatopleuric mesenchyme">Somatopleuric mesenchyme</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Development_of_the_human_body82" 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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Human_development" title="Template:Human development"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Human_development" title="Template talk:Human development"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Human_development" title="Special:EditPage/Template:Human development"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Development_of_the_human_body82" style="font-size:114%;margin:0 4em"><a href="/wiki/Development_of_the_human_body" title="Development of the human body">Development of the human body</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Before birth</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Prenatal_development" title="Prenatal development">Development</a></li> <li><a href="/wiki/Zygote" title="Zygote">Zygote</a></li> <li><a href="/wiki/Embryo" title="Embryo">Embryo</a></li> <li><a href="/wiki/Fetus" title="Fetus">Fetus</a></li> <li><a href="/wiki/Gestational_age_(obstetrics)" class="mw-redirect" title="Gestational age (obstetrics)">Gestational age</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Birth and after</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Childbirth" title="Childbirth">Birth</a></li> <li><a href="/wiki/Child_development" title="Child development">Child development</a> <ul><li><a href="/wiki/Child_development_stages" title="Child development stages">Stages</a></li> <li><a href="/wiki/Early_childhood_development" title="Early childhood development">Early</a></li> <li><a href="/wiki/Puberty" title="Puberty">Puberty</a></li></ul></li> <li><a href="/wiki/Adult_development" title="Adult development">Adult development</a></li> <li><a href="/wiki/Ageing" title="Ageing">Ageing</a></li> <li><a href="/wiki/Senescence" title="Senescence">Senescence</a></li> <li><a href="/wiki/Death" title="Death">Death</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Phases</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Early years <ul><li><a href="/wiki/Infant" title="Infant">Infant</a></li> <li><a href="/wiki/Toddler" title="Toddler">Toddler</a></li> <li><a href="/wiki/Early_childhood" title="Early childhood">Early childhood</a></li> <li><a href="/wiki/Childhood" class="mw-redirect" title="Childhood">Childhood</a> <ul><li><a href="/wiki/Child" title="Child">Child</a></li></ul></li></ul></li> <li><a href="/wiki/Youth" title="Youth">Youth</a> <ul><li><a href="/wiki/Preadolescence" title="Preadolescence">Preadolescence</a></li> <li><a href="/wiki/Adolescence" title="Adolescence">Adolescence</a></li> <li><a href="/wiki/Emerging_adulthood_and_early_adulthood" title="Emerging adulthood and early adulthood">Emerging adulthood</a></li></ul></li> <li><a href="/wiki/Adult" title="Adult">Adulthood</a> <ul><li><a href="/wiki/Young_adult" title="Young adult">Young adult</a></li> <li><a href="/wiki/Middle_age" title="Middle age">Middle adult</a></li> <li><a href="/wiki/Old_age" title="Old age">Elder adult</a></li></ul></li> <li><a href="/wiki/Dying" title="Dying">Dying</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Social and legal</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Minor_(law)" title="Minor (law)">Minor</a></li> <li><a href="/wiki/Age_of_majority" title="Age of majority">Age of majority</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Developmental_biology25" 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" style="background: thistle"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Developmental_biology" title="Template:Developmental biology"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Developmental_biology" title="Template talk:Developmental biology"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Developmental_biology" title="Special:EditPage/Template:Developmental biology"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Developmental_biology25" style="font-size:114%;margin:0 4em"><a href="/wiki/Developmental_biology" title="Developmental biology">Developmental biology</a></div></th></tr><tr><td colspan="2" class="navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ageing" title="Ageing">Ageing</a></li> <li><a href="/wiki/Compartment_(development)" title="Compartment (development)">Compartment</a></li> <li><a href="/wiki/Embryogenesis" class="mw-redirect" title="Embryogenesis">Embryogenesis</a> <ul><li><a href="/wiki/Human_embryogenesis" class="mw-redirect" title="Human embryogenesis">Human</a></li> <li><a href="/wiki/Drosophila_embryogenesis" title="Drosophila embryogenesis"><i>Drosophila</i></a></li> <li><a href="/wiki/Fish_development" title="Fish development">Fish</a></li> <li><a href="/wiki/Polarity_in_embryogenesis" title="Polarity in embryogenesis">polarity</a></li></ul></li> <li><a href="/wiki/Embryology" title="Embryology">Embryology</a></li> <li><a href="/wiki/Metamerism_(biology)" title="Metamerism (biology)">Metamerism</a></li> <li><a href="/wiki/Larva" title="Larva">Larva</a></li> <li><a href="/wiki/Pupa" title="Pupa">Pupa</a></li> <li><a href="/wiki/Metamorphosis" title="Metamorphosis">Metamorphosis</a> <ul><li>Indirect development: <a href="/wiki/Holometabolism" title="Holometabolism">holometabolism</a> (<a href="/wiki/Hypermetamorphosis" title="Hypermetamorphosis">Hypermetamorphosis</a>), <a href="/wiki/Hemimetabolism" title="Hemimetabolism">hemimetabolism</a></li> <li><a href="/wiki/Direct_development" title="Direct development">Direct development</a>: <a href="/wiki/Ametabolism" title="Ametabolism">ametabolism</a></li></ul></li> <li><a href="/wiki/Model_organism" title="Model organism">Model organisms</a></li> <li><a href="/wiki/Ontogeny" title="Ontogeny">Ontogeny</a></li> <li><a href="/wiki/Puberty" title="Puberty">Puberty</a></li> <li><a href="/wiki/Regeneration_(biology)" title="Regeneration (biology)">Regeneration</a> <ul><li><a href="/wiki/Regeneration_in_humans" title="Regeneration in humans">Human</a></li></ul></li> <li><a href="/wiki/Teratology" title="Teratology">Teratology</a></li></ul> </div></td></tr><tr><td colspan="2" class="navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Evolutionary_developmental_biology" title="Evolutionary developmental biology">Evolutionary developmental biology</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Pregnancy_and_childbirth184" style="padding:3px"><table class="nowraplinks mw-collapsible mw-collapsed 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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Pregnancy" title="Template:Pregnancy"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Pregnancy" title="Template talk:Pregnancy"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Pregnancy" title="Special:EditPage/Template:Pregnancy"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Pregnancy_and_childbirth184" style="font-size:114%;margin:0 4em"><a href="/wiki/Pregnancy" title="Pregnancy">Pregnancy</a> and <a href="/wiki/Childbirth" title="Childbirth">childbirth</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Family_planning" title="Family planning">Planning</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Birth_control" title="Birth control">Birth control</a></li> <li><a href="/wiki/Natural_family_planning" title="Natural family planning">Natural family planning</a></li> <li><a href="/wiki/Male_contraceptive" title="Male contraceptive">Male contraceptive</a></li> <li><a href="/wiki/Pre-conception_counseling" title="Pre-conception counseling">Pre-conception counseling</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Human_fertilization" title="Human fertilization">Conception</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Assisted_reproductive_technology" title="Assisted reproductive technology">Assisted reproductive technology</a> <ul><li><a href="/wiki/Artificial_insemination" title="Artificial insemination">artificial insemination</a></li> <li><a href="/wiki/Fertility_fraud" title="Fertility fraud">fertility fraud</a></li> <li><a href="/wiki/Fertility_medication" title="Fertility medication">fertility medication</a></li> <li><a href="/wiki/In_vitro_fertilisation" title="In vitro fertilisation">in vitro fertilisation</a></li> <li><a href="/wiki/Partner-assisted_reproduction" title="Partner-assisted reproduction">partner-assisted reproduction</a></li></ul></li> <li><a href="/wiki/Fertility_awareness" title="Fertility awareness">Fertility awareness</a></li> <li><a href="/wiki/Unintended_pregnancy" title="Unintended pregnancy">Unintended pregnancy</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Testing</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/3D_ultrasound" title="3D ultrasound">3D ultrasound</a></li> <li><a href="/wiki/Obstetric_ultrasonography" title="Obstetric ultrasonography">Obstetric ultrasonography</a></li> <li><a href="/wiki/Pregnancy_test" title="Pregnancy test">Pregnancy test</a> <ul><li><a href="/wiki/HCG_pregnancy_strip_test" class="mw-redirect" title="HCG pregnancy strip test">home testing</a></li></ul></li> <li><a href="/wiki/Prenatal_testing" title="Prenatal testing">Prenatal testing</a></li> <li><a href="/wiki/Medical_imaging_in_pregnancy" title="Medical imaging in pregnancy">Medical imaging</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Types</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cervical_pregnancy" title="Cervical pregnancy">Cervical</a></li> <li><a href="/wiki/Cryptic_pregnancy" title="Cryptic pregnancy">Cryptic</a></li> <li><a href="/wiki/Ectopic_pregnancy" title="Ectopic pregnancy">Ectopic</a></li> <li><a href="/wiki/Abdominal_pregnancy" title="Abdominal pregnancy">Abdominal</a></li> <li><a href="/wiki/Heterotopic_pregnancy" title="Heterotopic pregnancy">Heterotopic</a></li> <li><a href="/wiki/Molar_pregnancy" title="Molar pregnancy">Molar</a></li> <li><a href="/wiki/Ovarian_pregnancy" title="Ovarian pregnancy">Ovarian</a></li> <li><a href="/wiki/Postterm_pregnancy" title="Postterm pregnancy">Postterm</a></li> <li><a href="/wiki/Unintended_pregnancy" title="Unintended pregnancy">Unintended</a></li> <li><a href="/wiki/Interstitial_pregnancy" title="Interstitial pregnancy">Interstitial</a></li> <li><a href="/wiki/Rudimentary_horn_pregnancy" title="Rudimentary horn pregnancy">Rudimentary horn</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Childbirth" title="Childbirth">Childbirth</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%">Preparation</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/Bradley_method_of_natural_childbirth" title="Bradley method of natural childbirth">Bradley method</a></li> <li><a href="/wiki/Lamaze_technique" title="Lamaze technique">Lamaze</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Roles</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/Mother" title="Mother">Mother</a></li> <li><a href="/wiki/Infant" title="Infant">Newborn</a> <ul><li><a href="/wiki/Preterm_birth" title="Preterm birth">Preterm birth</a></li></ul></li> <li><a href="/wiki/Postterm_pregnancy" title="Postterm pregnancy">Postterm pregnancy</a></li> <li><a href="/wiki/Doula" title="Doula">Doula</a></li> <li><a href="/wiki/Birth_attendant" title="Birth attendant">Birth attendant</a></li> <li><a href="/wiki/Men%27s_role_in_childbirth" title="Men's role in childbirth">Men's roles</a></li> <li><a href="/wiki/Midwife" title="Midwife">Midwife</a> <ul><li><a href="/wiki/Auxiliary_nurse_midwife" title="Auxiliary nurse midwife">Auxiliary nurse midwife</a></li></ul></li> <li><a href="/wiki/Obstetrics_and_gynaecology" title="Obstetrics and gynaecology">Obstetrician</a></li> <li><a href="/wiki/Obstetrical_nursing" title="Obstetrical nursing">Perinatal nurse</a></li> <li><a href="/wiki/Traditional_birth_attendant" title="Traditional birth attendant">Traditional birth attendant</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Delivery</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/Pelvimetry" title="Pelvimetry">Pelvimetry</a> / <a href="/wiki/Bishop_score" title="Bishop score">Bishop score</a> <ul><li><a href="/wiki/Cervical_dilation" title="Cervical dilation">cervical dilation</a></li> <li><a href="/wiki/Cervical_effacement" title="Cervical effacement">cervical effacement</a></li> <li><a href="/wiki/Position_(obstetrics)" title="Position (obstetrics)">position</a></li></ul></li> <li><a href="/wiki/Bloody_show" title="Bloody show">Bloody show</a></li> <li><a href="/wiki/Uterine_contraction" title="Uterine contraction">Uterine contraction</a></li> <li><a href="/wiki/Vaginal_delivery" title="Vaginal delivery">Vaginal delivery</a></li> <li><a href="/wiki/Presentation_(obstetrics)" title="Presentation (obstetrics)">Presentation</a> <ul><li><a href="/wiki/Breech_birth" title="Breech birth">breech</a></li> <li><a href="/wiki/Cephalic_presentation" title="Cephalic presentation">cephalic</a></li> <li><a href="/wiki/Shoulder_presentation" title="Shoulder presentation">shoulder</a></li></ul></li> <li><a href="/wiki/Rupture_of_membranes" title="Rupture of membranes">Rupture of membranes</a></li> <li><a href="/wiki/Caesarean_section" title="Caesarean section">Caesarean</a></li> <li><a href="/wiki/Childbirth_positions" title="Childbirth positions">Childbirth positions</a></li> <li><a href="/wiki/Home_birth" title="Home birth">Home birth</a></li> <li><a href="/wiki/Labor_induction" title="Labor induction">Labor induction</a></li> <li><a href="/wiki/Multiple_birth" title="Multiple birth">Multiple birth</a></li> <li><a href="/wiki/Natural_childbirth" title="Natural childbirth">Natural childbirth</a></li> <li><a href="/wiki/Silent_birth" title="Silent birth">Silent birth</a></li> <li><a href="/wiki/Unassisted_childbirth" title="Unassisted childbirth">Unassisted childbirth</a></li> <li><a href="/wiki/Water_birth" title="Water birth">Water birth</a></li> <li><a href="/wiki/Placental_expulsion" title="Placental expulsion">Placental expulsion</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Prenatal</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%">Anatomy</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/Amniotic_fluid" title="Amniotic fluid">Amniotic fluid</a></li> <li><a href="/wiki/Amniotic_sac" title="Amniotic sac">Amniotic sac</a></li> <li><a href="/wiki/Endometrium" title="Endometrium">Endometrium</a></li> <li><a href="/wiki/Placenta" title="Placenta">Placenta</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Prenatal_development" title="Prenatal development">Development</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 class="mw-selflink selflink">Embryo</a></li> <li><a href="/wiki/Fetus" title="Fetus">Fetus</a></li> <li><a href="/wiki/Fundal_height" title="Fundal height">Fundal height</a></li> <li><a href="/wiki/Gestational_age" title="Gestational age">Gestational age</a></li> <li><a href="/wiki/Maternal_physiological_changes_in_pregnancy" title="Maternal physiological changes in pregnancy">Maternal physiological changes</a></li> <li><a href="/wiki/Postpartum_physiological_changes" title="Postpartum physiological changes">Postpartum physiological changes</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Prenatal_care" title="Prenatal care">Care</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/Brain_health_and_pollution" title="Brain health and pollution">Brain health and pollution</a></li> <li>Nutrition <ul><li><a href="/wiki/Environmental_toxicants_and_fetal_development" title="Environmental toxicants and fetal development">environmental toxicants</a></li> <li><a href="/wiki/Nutrition_and_pregnancy" title="Nutrition and pregnancy">in pregnancy</a></li> <li><a href="/wiki/Prenatal_nutrition" title="Prenatal nutrition">prenatal</a></li></ul></li> <li><a href="/wiki/Antenatal_depression" title="Antenatal depression">Prenatal depression</a></li> <li><a href="/wiki/Immunization_during_pregnancy" title="Immunization during pregnancy">Immunization</a></li> <li>Concomitant conditions <ul><li><a href="/wiki/Anemia_in_pregnancy" title="Anemia in pregnancy">Anemia</a></li> <li><a href="/wiki/Hypertensive_disease_of_pregnancy" title="Hypertensive disease of pregnancy">Hypertension</a></li> <li><a href="/wiki/Hypercoagulability_in_pregnancy" title="Hypercoagulability in pregnancy">Hypercoagulability</a></li> <li><a href="/wiki/Drugs_in_pregnancy" title="Drugs in pregnancy">Substance use</a> <ul><li><a href="/wiki/Smoking_and_pregnancy" title="Smoking and pregnancy">Smoking</a></li> <li><a href="/wiki/Alcohol_and_pregnancy" class="mw-redirect" title="Alcohol and pregnancy">Alcohol</a></li> <li><a href="/wiki/Cannabis_in_pregnancy" title="Cannabis in pregnancy">Cannabis</a></li> <li><a href="/wiki/Opioids_and_pregnancy" title="Opioids and pregnancy">Opioids</a></li></ul></li> <li>Endocrine diseases <ul><li><a href="/wiki/Diabetes_and_pregnancy" title="Diabetes and pregnancy">Diabetes</a></li> <li><a href="/wiki/Thyroid_disease_in_pregnancy" title="Thyroid disease in pregnancy">Thyroid disease</a></li></ul></li> <li>Liver diseases <ul><li><a href="/wiki/Acute_fatty_liver_of_pregnancy" title="Acute fatty liver of pregnancy">Acute fatty liver</a></li> <li><a href="/wiki/Intrahepatic_cholestasis_of_pregnancy" title="Intrahepatic cholestasis of pregnancy">Intrahepatic cholestasis</a></li></ul></li> <li>Infections <ul><li><a href="/wiki/HIV_and_pregnancy" title="HIV and pregnancy">HIV</a></li> <li><a href="/wiki/COVID-19_in_pregnancy" title="COVID-19 in pregnancy">COVID-19</a></li> <li><a href="/wiki/HCV_in_children_and_pregnancy" title="HCV in children and pregnancy">Hepatitis C</a></li> <li><a href="/wiki/Pregnancy-associated_malaria" title="Pregnancy-associated malaria">Malaria</a></li></ul></li> <li>Skin diseases <ul><li><a href="/wiki/Lupus_and_pregnancy" title="Lupus and pregnancy">Lupus</a></li> <li><a href="/wiki/Pruritic_folliculitis_of_pregnancy" title="Pruritic folliculitis of pregnancy">Pruritic folliculitis</a></li> <li><a href="/wiki/Dermatoses_of_pregnancy" title="Dermatoses of pregnancy">Dermatoses</a></li></ul></li> <li>Others <ul><li><a href="/wiki/Drugs_in_pregnancy" title="Drugs in pregnancy">Drugs</a></li> <li><a href="/wiki/Vaginal_flora_in_pregnancy" title="Vaginal flora in pregnancy">Vaginal flora</a></li> <li><a href="/wiki/Obstetrical_bleeding" title="Obstetrical bleeding">Bleeding</a></li> <li><a href="/wiki/Motor_vehicle_emissions_and_pregnancy" class="mw-redirect" title="Motor vehicle emissions and pregnancy">Motor vehicle emissions</a></li> <li><a href="/wiki/Pre-existing_disease_in_pregnancy" title="Pre-existing disease in pregnancy">Pre-existing disease</a></li> <li><a href="/wiki/Pregnancy_and_sleep" title="Pregnancy and sleep">Sleep</a></li></ul></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Procedures</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/Amniocentesis" title="Amniocentesis">Amniocentesis</a></li> <li><a href="/wiki/Cardiotocography" title="Cardiotocography">Cardiotocography</a></li> <li><a href="/wiki/Chorionic_villus_sampling" title="Chorionic villus sampling">Chorionic villus sampling</a></li> <li><a href="/wiki/Nonstress_test" title="Nonstress test">Nonstress test</a></li> <li><a href="/wiki/Abortion" title="Abortion">Abortion</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/Postpartum_period" title="Postpartum period">Postpartum</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%">Maternal</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/Lochia" title="Lochia">Lochia</a></li> <li><a href="/wiki/Postpartum_care" title="Postpartum care">Postpartum care</a></li> <li><a href="/wiki/Postpartum_depression" title="Postpartum depression">Postpartum depression</a></li> <li><a href="/wiki/Postpartum_confinement" title="Postpartum confinement">Postpartum confinement</a></li> <li><a href="/wiki/Sex_after_pregnancy" title="Sex after pregnancy">Sex after pregnancy</a></li> <li><a href="/wiki/Psychiatric_disorders_of_childbirth" title="Psychiatric disorders of childbirth">Psychiatric disorders of childbirth</a></li> <li><a href="/wiki/Postpartum_physiological_changes" title="Postpartum physiological changes">Postpartum physiological changes</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Roles</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/Doula" title="Doula">Doula</a></li> <li><a href="/wiki/Health_visitor" title="Health visitor">Health visitor</a></li> <li><a href="/wiki/Lactation_consultant" title="Lactation consultant">Lactation consultant</a></li> <li><a href="/wiki/Monthly_nurse" title="Monthly nurse">Monthly nurse</a></li> <li><a href="/wiki/Nanny#Maternity_nurse_/_newborn_care_specialists_/_confinement_nanny" title="Nanny">Confinement nanny</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Infant</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/Adaptation_to_extrauterine_life" title="Adaptation to extrauterine life">Adaptation to extrauterine life</a></li> <li><a href="/wiki/Apgar_score" title="Apgar score">Apgar score</a></li> <li><a href="/wiki/Child_care" title="Child care">Child care</a></li> <li><a href="/wiki/Birth_defect" title="Birth defect">Congenital disorders</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Obstetric history</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Gravidity_and_parity" title="Gravidity and parity">Gravidity and parity</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Parental_brain" title="Parental brain">Parental brain</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"><style data-mw-deduplicate="TemplateStyles:r1038841319">.mw-parser-output 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