allantois
[uh-lan-toh-is, -tois]
- a vascular, extraembryonic membrane of birds, reptiles, and certain mammals that develops as a sac or diverticulum from the ventral wall of the hindgut.
Show More
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)
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for allantois
Historical Examples
So the allantois of the reptile has become the placenta of the mammal.
The Meaning of EvolutionSamuel Christian Schmucker
The function of the allantois is still in a great measure unknown.
A System of MidwiferyEdward Rigby
The cavity of the allantois, if developed, vanishes completely.
The Works of Francis Maitland Balfour, Volume III (of 4)Francis Maitland Balfour
It thus comes about that the further splitting of the mesoblast merely enlarges the cavity in which the allantois lies.
The Works of Francis Maitland Balfour, Volume III (of 4)Francis Maitland Balfour
As the allantois increases in size and importance, the allantoic vessels are correspondingly developed.
The Works of Francis Maitland Balfour, Volume III (of 4)Francis Maitland Balfour
allantois
- 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
Show More
Word Origin
C17: New Latin, irregularly from Greek allantoeidēs sausage-shaped, allantoid
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-lăn′tō-ĭs)- 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
Show More
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
allantois
[ə-lăn′tō-ĭs]
- 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.
Show More
The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.