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Archenteron
open-in-new
<h2 id="formation-in-sea-urchins">Formation in sea urchins</h2> <p class="note">Further information: <a href="/facts/Gastrulation/kN8X10mK">Gastrulation</a></p> <p>As <a href="/facts/Primary_mesenchyme/W0jeK2a3">primary mesenchyme</a> cells detach from the <a href="/facts/Vegetal_pole/fIxIfCtn">vegetal pole</a> in the gastrula and enter the fluid-filled cavity in the center (the <a href="/facts/Blastocoel/QQUUs93N">blastocoel</a>), the remaining cells at the vegetal pole flatten to form a vegetal plate. This buckles inwards towards the blastocoel in a process called <a href="/facts/Invagination/Mn2oqmxu">invagination</a>. The cells continue to be rearranged until the shallow dip formed by invagination transforms into a deeper, narrower pouch formed by the <a href="/facts/Gastrula/kN8X10mK">gastrula</a>'s <a href="/facts/Endoderm/6UhPjVnt">endoderm</a>. This pouch narrows and lengthens to become the archenteron, a process driven by <a href="/facts/Convergent_extension/vsEfjptS">convergent extension</a>. The open end of the archenteron is called the <a href="/facts/Blastopore/kN8X10mK">blastopore</a>. </p> <p>The <a href="/facts/Filopodia/wA6xunR3">filopodia</a>—thin fibers formed by the mesenchyme cells, found in late gastrulation—contract to drag the tip of the archenteron across the blastocoel. The endoderm of the archenteron will fuse with the <a href="/facts/Ectoderm/lg5p0jTL">ectoderm</a> of the blastocoel wall. At this point gastrulation is complete, and the embryo has a functional digestive tube. </p> <h2 id="similar-formation-process-in-other-animals">Similar formation process in other animals</h2> <p>The indentation that is actually formed is called the lip of the <a href="/facts/Blastopore/kN8X10mK">blastopore</a> or the <a href="/facts/Dorsal_lip/VabbGwUD">dorsal lip</a> in <a href="/facts/Amphibian/r2BleD2W">amphibians</a> and <a href="/facts/Fish/fln4gH9V">fish</a>, and the <a href="/facts/Primitive_streak/HTrnV8db">primitive streak</a> in <a href="/facts/Bird/RJF6zwLP">birds</a> and <a href="/facts/Mammal/phSwTzBo">mammals</a>. Each is controlled by the dorsal lip and <a href="/facts/Primitive_node/U0mFBr2q">primitive node</a> (also known as Hensen's node), respectively. </p><p>During <a href="/facts/Gastrulation/kN8X10mK">gastrulation</a>, the archenteron develops into the digestive tube, with the <a href="/facts/Blastopore/kN8X10mK">blastopore</a> developing into either the mouth (in <a href="/facts/Protostome/XLtWYdt8">protostomes</a>) or the anus (in <a href="/facts/Deuterostome/Uc3V9mGA">deuterostomes</a>). </p> <h2 id="external-links">External links</h2> <ul><li><a href="https://web.archive.org/web/20110709192109/http://chsweb.lr.k12.nj.us/mstanley/outlines/animals/antax/image51.gif">Diagram</a></li></ul>