yolk sac
A membranous sac attached to an embryo, providing early nourishment in the form of…A membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals.
» The umbilical cord develops by the fifth week of embryonic development, replacing the yolk sac as the embryo's nutrient source.
Meaning
1 sensesA membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals.
membranous structure enclosing the yolk of eggs in birds, reptiles, marsupials, and some fishes; circulates nutrients to the developing embryo
Examples
1 sentencesThe umbilical cord develops by the fifth week of embryonic development, replacing the yolk sac as the embryo's nutrient source.
Forms
plural: yolk sacsSynonyms
3 synonyms- membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional:vitelline sacumbilical vesiclevesicula umbilicus