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allantois

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al⋅lan⋅to⋅is

[uh-lan-toh-is, -tois]
–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:
1640–50; < NL < Gk allantoeids, wrongly taken for pl. and given a sing., on the model of words like hērōís (sing.), hērōídes (pl.)
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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al·lan·to·is   (ə-lān'tō-ĭs)   
n.   pl. al·lan·to·i·des (āl'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. It is important in the formation of the umbilical cord and placenta in mammals. Also called allantoid.

[New Latin, from allantoīdes, from Greek allantoeidēs, sausage-shaped : allas, allant-, sausage + -oeidēs, -oid.]
al'lan·to'ic (āl'ən-tō'ĭk) adj.
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Medical Dictionary

Main Entry: al·lan·to·is
Pronunciation: &-'lant-&-w&s
Function: noun
Inflected Form: plural al·lan·to·ides /"al-&n-'tO-&-"dEz, "al-"an-/
: a vascular fetal membrane of reptiles, birds, or mammals that is formed as a pouch from thehindgut and that in placental mammals is intimately associated with the chorion in formation of the placenta
Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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Medical Dictionary

allantois al·lan·to·is (ə-lān'tō-ĭs)
n. pl. al·lan·to·i·des (āl'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. Also called allantoid.


al'lan·to'ic (āl'ən-tō'ĭk) adj.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Encyclopedia

allantois

an extra-embryonic membrane of reptiles, birds, and mammals arising as a pouch, or sac, from the hindgut. In reptiles and birds it expands greatly between two other membranes, the amnion and chorion, to serve as a temporary respiratory organ while its cavity stores fetal excretions. In mammals other than marsupials the allantois is intimately associated with the chorion, contributing blood vessels to that structure as it forms-in conjunction with the endometrium, or mucosal lining, of the uterus-the placenta

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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