yolk sac

noun

A membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals.

Similar
yolk bagvitelline sacumbilical vesiclevesicula umbilicus
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Meanings

nounyolk sac (plural yolk sacs)

plural yolk sacs

  1. anatomyA membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals.

    Synonyms: yolk bag

Synonyms & antonyms

nounA membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals.

Similar
yolk bag

More synonyms by meaning

nounmembranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional

Similar
vitelline sacumbilical vesiclevesicula umbilicus
Broader
sac
Also see
yolk bag

Synonym sets from Open English WordNet, CC BY 4.0.

Cite this entry
APA

yolk sac. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/yolk%20sac

MLA

“yolk sac.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/yolk%20sac. Accessed November 5, 2026.

Chicago

WatkinsX Dictionary, s.v. “yolk sac,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/yolk%20sac.

Source: yolk sac on Wiktionary, CC BY-SA 4.0.