Search Result for "yolk sac":
Wordnet 3.0

NOUN (2)

1. membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional;
[syn: yolk sac, vitelline sac, umbilical vesicle, vesicula umbilicus]

2. membranous structure enclosing the yolk of eggs in birds, reptiles, marsupials, and some fishes; circulates nutrients to the developing embryo;