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</div> </div> </div>  <body class="post-template-default single single-post postid-165068 single-format-standard wp-embed-responsive" itemtype="https://schema.org/WebPage" itemscope="itemscope"> <a class="skip-link screen-reader-text" href="#site-content">Skip to the content</a> <main class="main"> <br />  <section id="bby-main"> <div class="bby-container"> <div class="bby-content-wrapper"> <div class="bby-main-content justify-content-center"> <div class="bby-content-right"> <div class="bby-content-breadcrumb" itemscope itemtype="http://schema.org/BreadcrumbList"> <span itemprop="itemListElement" itemscope itemtype="http://schema.org/ListItem"> <a itemprop="item" href="https://www.bartleby.com"><span itemprop="name">Home</span></a> <meta itemprop="position" content="1" /> </span>  »  <span itemprop="itemListElement" itemscope itemtype="http://schema.org/ListItem"> <a itemprop="item" href="/lit-hub/anatomy-of-the-human-body/"><span itemprop="name">Anatomy of the Human Body</span></a> <meta itemprop="position" content="2" /> </span>  »  <span itemprop="itemListElement" itemscope itemtype="http://schema.org/ListItem"> <span itemprop="name" class="atm-mk-uncursor">6. The Neural Groove and Tube</span> <meta itemprop="position" content="3" /> </span> </div> <div class="bby-content-nav"> <div class="nav-prev"> <a href="/lit-hub/anatomy-of-the-human-body/5-segmentation-of-the-fertilized-ovum"> <i class="fa fa-angle-left" aria-hidden="true"></i> <label>Previous Article</label> </a> </div> <div class="nav-next"> <a href="/lit-hub/anatomy-of-the-human-body/7-the-notochord"> <label>Next Article</label> <i class="fa fa-angle-right" aria-hidden="true"></i> </a> </div> </div> <div class="bby-single-content bby-single-content-post"> <p class="bby-entry-meta-fields"><br> <a href="/lit-hub/anatomy-of-the-human-body/">Contents</a> -<a href="/lit-hub/anatomy-of-the-human-body/subject-index/">SUBJECT INDEX</a> -<a href="/lit-hub/bibliography/anatomy-of-the-human-body/">BIBLIOGRAPHIC RECORD</a> -<a href="/lit-hub/anatomy-of-the-human-body/illustrations/">ILLUSTRATION INDEX</a> </p> <p class="text-center">Henry Gray (1825–1861). Anatomy of the Human Body. 1918.</p> <h1 class="text-center">6. The Neural Groove and Tube</h1> <TR><TD>In front of the primitive streak two longitudinal ridges, caused by a folding up of the ectoderm, make their appearance, one on either side of the middle line <A HREF="/lit-hub/anatomy-of-the-human-body/fig-16">(Fig. 16</A>). These are named the <B>neural folds;</B> they commence some little distance behind the anterior end of the embryonic disk, where they are continuous with each other, and from there gradually extend backward, one on either side of the anterior end of the primitive streak. Between these folds is a shallow median groove, the <B>neural groove</B> (<A HREF="/lit-hub/anatomy-of-the-human-body/fig-16">Figs. 16,</A> <A HREF="/lit-hub/anatomy-of-the-human-body/fig-17">17</A>). The groove gradually deepens as the neural folds become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into a closed tube, the <B>neural tube</B> or <B>canal</B> <A HREF="/lit-hub/anatomy-of-the-human-body/fig-18">(Fig. 18),</A> the ectodermal wall of which forms the rudiment of the nervous system. After the coalescence of the neural folds over the anterior end of the primitive streak, the blastopore no longer opens on the surface but into the closed canal of the neural tube, and thus a transitory communication, the <B>neurenteric canal,</B> is established between the neural tube and the primitive digestive tube. The coalescence of the neural folds occurs first in the region of the hind-brain, and from there extends forward and backward; toward the end of the third week the front opening (anterior neuropore) of the tube finally closes at the anterior end of the future brain, and forms a recess which is in contact, for a time, with the overlying ectoderm; the hinder part of the neural groove presents for a time a rhomboidal shape, and to this expanded portion the term <B>sinus rhomboidalis</B> has been applied <A HREF="/lit-hub/anatomy-of-the-human-body/fig-18">(Fig. 18</A>). Before the neural groove is closed a ridge of ectodermal cells appears along the prominent margin of each neural fold; this is termed the <B>neural crest</B> or <B>ganglion ridge,</B> and from it the spinal and cranial nerve ganglia and the ganglia of the sympathetic nervous system are developed. By the upward growth of the mesoderm the neural tube is ultimately separated from the overlying ectoderm.</TD><TD VALIGN= TOP ALIGN=RIGHT><FONT SIZE="-2"><A NAME ="1"><I>   1</I></A></FONT></TD></TR> <TR><TD><BR><CENTER><A HREF="/lit-hub/anatomy-of-the-human-body/fig-18"><IMG WIDTH=189 HEIGHT=326 SRC="https://legacy-cms-media.bartleby.com/wp-content/uploads/sites/7/107/Images/small/image18.jpg" BORDER="0"></A><A NAME="i18"></A></CENTER></TD></TR><TR><TD><BR><CENTER><FONT SIZE="-1">F<FONT SIZE="-2">IG. </FONT>18– </FONT>Chick embryo of thirty-three hours’ incubation, viewed from the dorsal aspect. X 30. (From Duval’s “Atlas d’Embryologie.”) (<A HREF="/lit-hub/anatomy-of-the-human-body/fig-18">See enlarged image</A>)</CENTER></TD></TR><TR><TD> </TD></TR> <TR><TD>  The cephalic end of the neural groove exhibits several dilatations, which, when the tube is closed, assume the form of three vesicles; these constitute the three primary cerebral vesicles, and correspond respectively to the future <B>fore-brain</B> (<I>prosencephalon</I>), <B>mid-brain</B> (<I>mesencephalon</I>), and <B>hind-brain</B> (<I>rhombencephalon</I>) <A HREF="/lit-hub/anatomy-of-the-human-body/fig-18">(Fig. 18</A>). The walls of the vesicles are developed into the nervous tissue and neuroglia of the brain, and their cavities are modified to form its ventricles. The remainder of the tube forms the <B>medulla spinalis</B> or <B>spinal cord;</B> from its ectodermal wall the nervous and neuroglial elements of the medulla spinalis are developed while the cavity persists as the central canal.</TD><TD VALIGN= TOP ALIGN=RIGHT><FONT SIZE="-2"><A NAME ="2"><I>   2</I></A></FONT></TD></TR> </TABLE> <div class="bby-content-meta-footer-entry"> <p class="bby-entry-meta-fields"><br> <a href="/lit-hub/anatomy-of-the-human-body/">Contents</a> -<a href="/lit-hub/anatomy-of-the-human-body/subject-index/">SUBJECT INDEX</a> -<a href="/lit-hub/bibliography/anatomy-of-the-human-body/">BIBLIOGRAPHIC RECORD</a> -<a href="/lit-hub/anatomy-of-the-human-body/illustrations/">ILLUSTRATION INDEX</a> </p> </div> <div class="bby-content-nav"> <div class="nav-prev"> <a href="/lit-hub/anatomy-of-the-human-body/5-segmentation-of-the-fertilized-ovum"> <i class="fa fa-angle-left" aria-hidden="true"></i> <label>Previous Article</label> </a> </div> <div class="nav-next"> <a href="/lit-hub/anatomy-of-the-human-body/7-the-notochord"> <label>Next Article</label> <i class="fa fa-angle-right" aria-hidden="true"></i> </a> </div> </div> </div> </div> </div> </div> </div> </div> </section>  </main>   <footer id="bby-site-footer" class="bby-footer main-footer" itemtype="https://schema.org/WPFooter" itemscope="itemscope"> <div class="bby-footer-top-container d-flex"> <div class="bby-container d-flex align-items-start flex-row"> <div class="footer-top-left-container d-flex align-items-start flex-row"> <div class="footer-nav-wrapper"> <div class="widget widget_block"><div class="widget-content"> <div class="wp-block-group"><div class="wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow"> <figure class="wp-block-image size-full"><img loading="lazy" decoding="async" width="105" height="30" src="https://legacy-cms-media.bartleby.com/wp-content/uploads/sites/7/2022/11/14172410/bartleby-white.png" alt="" class="wp-image-175150" /></figure> </div></div> </div></div><div class="widget widget_block"><div class="widget-content"> <div class="wp-block-group"><div class="wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow"></div></div> </div></div> </div> <div class="footer-nav-wrapper"> <div class="widget widget_block"><div class="widget-content"><ul> <li><a href="/lit-hub/the-oxford-shakespeare/">Shakespeare</a></li> <li><a href="/lit-hub/the-holy-bible/">Bible</a></li> <li><a href="/lit-hub/the-elements-of-style/">Strunk</a></li> <li><a href="/lit-hub/nonfiction/">Nonfiction</a></li> <li><a href="/lit-hub/quotations/">Quotations</a></li> <li><a href="/lit-hub/reference/">Reference</a></li> </ul> <ul> <li><a href="/lit-hub/fiction/">Fiction</a></li> <li><a href="/lit-hub/anatomy-of-the-human-body/"> Anatomy</a></li> <li><a href="/lit-hub/hc/">Harvard Classics</a></li> <li><a href="/lit-hub/library/">Lit. 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