Meaning of allantois

al•lan•to•is

Pronunciation: (u-lan'tō-is, -tois), [key]
— n. Embryol., Zool.
  1. a vascular, extraembryonic membrane of birds, reptiles, and certain mammals that develops as a sac or diverticulum from the ventral wall of the hindgut.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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