MCAT Question A Day - 1/23/14 - Answer!

Which embryonic membrane is most closely associated with implantation?

A. Amnion

B. Chorion

C. Allantois

D. Yolk sac

The correct answer is (B). In humans, the blastocyst contains an inner cell mass from which the embryo develops and the trophoblast, which forms the chorion and chorionic villi. The chorionic villi form the attachment with the endometrial lining of the uterus during implantation.

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