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allantois
[ uh-lan-toh-is, -tois ]
noun
- 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
- 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
allantois
/ ə-ă′ō-ĭ /
, Plural allantoides ă′ɵ-ō′ĭ-ŧ′
- 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.
Derived Forms
- allantoic, adjective
yvlog History and Origins
Origin of allantois1
yvlog History and Origins
Origin of allantois1
Example Sentences
The division of Vertebrata in which the embryo develops an allantois.
In Mammalia the allantois is not so largely developed as in Birds, and it enters largely into the formation of the placenta.
The third is the chorion, forming the outer membrane which encloses the fetus, and within which is the amnion, or innermost membrane which surrounds the fetus, and between which is another membrane, called the allantois.
Diagram of chick showing relations of amnion, allantois and yolk.
The literal references to the foregoing are: am, amnion; al, allantois; v, vitellus; h, encephalon; i, eye; c, heart; f, liver; g, gizzard; ms, upper, and mi, lower member.
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