yolk sac
1 definition found
yolk sac - WordNet (r) 2.1 (2005) :
yolk sac
n 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
|