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Related to chorioallantois: chorioallantoic
an extraembryonic structure formed by union of the chorion and allantois, which by means of vessels in the associated mesoderm serves in gas exchange; in many mammals, it forms the placenta. adj., adj chorioallanto´ic.
Extraembryonic membrane formed by the fusion of the allantois with the serosa or false chorion. In mammalian embryos, it forms the fetal portion of the placenta; in avian embryos, it is fused with the shell.
The highly vascular fetal membrane that consists of the fused chorion and allantois, found adjacent to the eggshell in reptiles and birds and constituting the placenta in most mammals.
cho′ri·o·al′lan·to′ic (-ō-ăl′ən-tō′ĭk) adj.
Extraembryonic membrane formed by the fusion of the allantois with the serosa or false chorion. In mammals it forms the fetal portion of the placenta; in avian embryos it is fused with the shell.