al·lan·to·is ( -l n t - s)n. pl. al·lan·to·i·des ( l n-t-d z) 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 allanto  des, from Greek allantoeids, sausage-shaped : allas, allant-, sausage + -oeids, -oid.]al lan·toic (ln-tk) adj. |
allantois [ˌælənˈtəʊɪs əˈlæntɔɪs]
n
(Life Sciences & Allied Applications / Zoology) 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
[New Latin, irregularly from Greek allantoeidēs sausage-shaped, allantoid]
allantoic [ˌælənˈtəʊɪk] adj
| allantois (-lnt-s) Plural allantoides ( ln-t-dz) 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. |
ThesaurusLegend: Synonyms Related Words Antonyms
| Noun | 1. | allantois - the vascular fetal membrane that lies below the chorion and develops from the hindgut in many embryonic higher vertebrates (reptiles, birds and mammals) mammal, mammalian - any warm-blooded vertebrate having the skin more or less covered with hair; young are born alive except for the small subclass of monotremes and nourished with milk fetal membrane - any membrane that functions for the protection or nourishment or respiration or excretion of a developing fetus |
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