yolk sac, n.
membranous structure enclosing the yolk of eggs in birds, reptiles, marsupials, and some fishes; circulates nutrients to the developing embryo
<noun.animal>
yolk sac
semantic pointers
hypernym
membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional
<noun.animal>
umbilical vesicle vesicula umbilicus vitelline sac yolk sac
semantic pointers
hypernym