![chorioallantois chorioallantois](https://www.tekportal.net/wp-content/uploads/2018/12/chorioallantois.jpg)
chorioallantois [kawr-ee-oh-uh-lan-toh-is, ‐tois, kohr‐] Word Origin noun Embryology, Zoology.
- a vascular, extraembryonic membrane of birds, reptiles, and certain mammals, formed by the fusion of the wall of the chorion with the wall of the allantois.
Origin of chorioallantois First recorded in 1930–35 Also called chorioallantoic membrane. Related formscho·ri·o·al·lan·to·ic [‐al-uh n-toh-ik] /‐ˌæl ənˈtoʊ ɪk/, adjective chorioallantois in Medicine chorioallantois [kôr′ē-ō′ə-lăn′tō-ĭs] n.
- The highly vascular extraembryonic membrane formed by the fusion of the allantois with the chorion that constitutes the placenta in most mammals.
Related formscho′ri•o•al′lan•to′ic (-ō-ăl′ən-tō′ĭk) adj.