In this diagram,what is the structure labeled A called?
A)Yolk sac
B)Amnionic cavity
C)Trophoblast
D)Embryonic disc

Question

In this diagram,what is the structure labeled A called? 
A)Yolk sac 
B)Amnionic cavity 
C)Trophoblast 
D)Embryonic disc

Quizplus · Accepted Answer

The structure labeled A is the embryonic disc, which is the precursor to the embryo. The yolk sac (A) is a membrane that provides nutrients to the embryo in some animals; the amniotic cavity (B) is the fluid-filled sac that surrounds the embryo and provides protection; and the trophoblast (C) is the outer layer of cells that will eventually form the placenta.

In This Diagram,what Is the Structure Labeled a Called