The embryonic layer that invades the lining of the uterus and forms the placenta is the
A) trophoblast.
B) embryoblast.
C) inner cell mass.
D) endometrium.

Question

Quizplus · Accepted Answer

The trophoblast is the outermost layer of cells in the blastocyst that will eventually form the placenta. It invades the lining of the uterus and begins to form connections with the mother's blood vessels. The embryoblast is the inner cell mass that will develop into the embryo itself, but it does not directly form the placenta. The endometrium is the lining of the uterus that the blastocyst implants into, but it is not a layer of the embryo.

The Embryonic Layer That Invades the Lining of the Uterus