EXAMPLES | WORD ORIGIN noun . Embryology, Zoology a vascular, extraembryonic membrane of birds, reptiles, and certain mammals that develops as a sac or diverticulum from the ventral wall of the hindgut. Origin of allantois 1640–50; < New Latin < Greek allantoeidḗs, wrongly taken for plural and given a singular, on the model of words like hērōís (singular), hērōídes (plural)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for allantois Historical Examples of allantois British Dictionary definitions for allantois noun a membranous sac growing out of the ventral surface of the hind gut of embryonic reptiles, birds, and mammals. It combines with the chorion to form the mammalian placenta Derived Forms allantoic ( ˌælənˈtəʊɪk), adjective Word Origin for allantois
C17: New Latin, irregularly from Greek
allantoeidēs sausage-shaped, allantoid
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
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n. pl. al•lan•to•i•des ( ăl′ən-tō) ′ĭ-dēz′ A membranous sac that develops from the posterior part of the alimentary canal in the embryos of mammals, birds, and reptiles, and is important in the formation of the umbilical cord and placenta in mammals. allantoid Related forms al′lan•to ( ′ic ăl′ən-tō) ′ĭk adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Plural allantoides ( ăl′ən-tō) ′ĭ-dēz′ A membranous sac that grows out of the lower end of the alimentary canal in embryos of reptiles, birds, and mammals. In mammals, the blood vessels of the allantois develop into the blood vessels of the umbilical cord.
The American Heritage® Science Dictionary
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