bilaminar blastocyst

This bilaminar blastocyst also defines the primitive dorsal ventral axis.

Bilaminar blastocyst or Bilaminar disc refers to the epiblast and the hypoblast, evolved from the embryoblast.

The final two layers of the embryoblast are known collectively as the bilaminar embryonic disc as well as the bilaminar blastocyst or bilaminar blastoderm.

During gastrulation, cells of the epiblast, a layer of the bilaminar blastocyst, migrate towards the primitive streak, enter it, and then move apart from it through a process called ingression.

Next is the development of bilaminar blastocyst, in which a separation of cells to form the embryoblast and trophoblast, along with the primitive yolk sac, which subsequently differentiates to secondary or definitive yolk sac.