allantois /əlan″tois/ [Gk, allas, sausage, eidos, form] , a tubular extension of the endoderm of the yolk sac that extends with the allantoic vessels into the connecting stalk of the embryo. In human embryos, allantoic vessels become the umbilical vessels and the chorionic villi. See also body stalk, umbilical cord. −allantoic, adj.
