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Gastrulation - Anatomy & Physiology (view source)
Revision as of 13:26, 25 August 2008
, 13:26, 25 August 2008no edit summary
*The endoderm and mesoderm develop by proliferation and migration of cells of the epiblast.
*The endoderm and mesoderm develop by proliferation and migration of cells of the epiblast.
**What remains of the epiblast forms the ectoderm.
**What remains of the epiblast forms the ectoderm.
*The epiblast is a circular plate of cells. In gastrulation, cells ingress ventrally from the epiblast to form the three germ layers.
*Gastrulation occurs at three embryonic sites:
*Gastrulation occurs at three embryonic sites:
::'''Primitive Streak'''
::'''Primitive Streak'''
::'''Node'''
::'''Node'''
::'''Tail Bud'''
::'''Tail Bud'''
==Gastrulation at the Primitive Streak==
*The epiblast is a simple circular plate of cells.
*Cells proliferate and through migration, converge at one pole of the epiblast. These cells become columnar to compensate for the decreased amount of space available.
**This defines the posterior of the embryo.
*Eventually, convergence causes cells to be displaced anteriorly. As more cells converge, the primitive streak elongates.
*Cells in the primitive groove change shape from columnar to wedge shaped, which produces two elevations either side of a groove.
*Epiblastic cells of the primitive streak begin to ingress ventrally to form the new germ layers.