Hypoblast
EMBRYONIC INNER CELL MASS TISSUE THAT FORMS THE YOLK SAC AND, LATER, CHORION
Endoblast; Primitive endoderm; Anterior visceral endoderm
In amniote embryology, the hypoblast, is one of two distinct layers arising from the inner cell mass in the mammalian blastocyst, or from the blastodisc in reptiles and birds. The hypoblast gives rise to the yolk sac, which in turn gives rise to the chorion.