Changes

==Gastrulation at the Primitive Streak==

==Gastrulation at the Primitive Streak==

*The epiblast is a simple circular plate of cells.

*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.  

*Cells proliferate and converge through migration, 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.

**This defines the posterior of the embryo.

*Eventually, convergence causes cells to be displaced anteriorly. As more cells converge, the primitive streak elongates.   

*Eventually, convergence causes cells to be displaced anteriorly. As more cells converge, the primitive streak elongates.