The yolk sac of humans
A) stores nutrients to support the developing embryo.
B) is evidence of humans' relationships with egg-laying vertebrates.
C) secretes HCG.
D) absorbs nutrients from, and releases waste to, the mother's blood.

Question

Quizplus · Accepted Answer

The human yolk sac does not store nutrients for the embryo, secrete HCG, or exchange nutrients and wastes with the mother's blood. Instead, it serves as evidence of the evolutionary history of humans, indicating a common ancestry with egg-laying vertebrates. This is because the yolk sac is a vestigial structure that in egg-laying animals would store nutrients for the developing embryo. In humans, it is involved in early blood cell formation and development of the gut, but its presence reflects evolutionary history rather than a functional role in nutrition.

The Yolk Sac of Humans