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allantois

[ uh-lan-toh-is, -tois ]

noun

, Embryology, Zoology.
  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.


allantois

/ ˌælənˈtəʊɪk; əˈlæntɔɪs; ˌælənˈtəʊɪs /

noun

  1. 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
“Collins English Dictionary — Complete & Unabridged” 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012


allantois

/ ə-lăntō-ĭs /

, Plural allantoides ăl′ən-tōĭ-dēz′

  1. 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.


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Derived Forms

  • allantoic, adjective
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Word History and Origins

Origin of allantois1

1640–50; < New Latin < Greek allantoeidḗs, wrongly taken for plural and given a singular, on the model of words like hērōís (singular), hērōídes (plural)
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Word History and Origins

Origin of allantois1

C17: New Latin, irregularly from Greek allantoeidēs sausage-shaped, allantoid
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Example Sentences

The cavity of the allantois, if developed, vanishes completely.

This bag is called the allantois, and serves as a sort of lung for the developing chick.

It draws its oxygen and throws off its wastes through the instrumentality of the allantois, which covers it over.

The blood vessels of the allantois take in oxygen and give out carbon dioxide through the porous shell.

The allantois of the chick now gains a new development and an altered function.

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allantoinalla prima