The First Extraembryonic Membrane to Appear is The

Question

The first extraembryonic membrane to appear is the
A)chorion.
B)allantois.
C)placenta.
D)yolk sac.
E)amnion.

Accepted Answer

The yolk sac is the first extraembryonic membrane to appear in developing embryos, and is important for providing nutrients to the developing embryo. The other listed extraembryonic membranes (chorion, allantois, placenta, and amnion) appear later in development.