Characteristic Features of Avian Gastrulation

• Creation of hypoblast and its important role in formation of the axis and orientation of embryo.
• Existence of the cells of all the three germinal areas in the epiblast.
• Creation of the primitive streak and its regression in law stages of gastrulation.
• Nonexistence of archenteron formation.
• Gastrula cell movements include poly invagination, involution, convergence, divergence and epiboly.
• Cephalocaudal separation of axial structures and growth of the embryo during gastrulation.