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
Derived forms
allantoic (ˌælənˈtəʊɪk)
adjective
Word origin
C17: New Latin, irregularly from Greek allantoeidēs sausage-shaped, allantoid
a membranous pouch with a rich blood supply in the embryos of birds, reptiles, and mammals: it is an organ of respiration and excretion for embryonic birds and reptiles: in mammals it helps form the placenta
Word origin
ModL < Gr allantoeidēs, sausage-shaped < allas, sausage (prob. < dial. allē, garlic, via Oscan *allo < L alium, allium) + -eidēs, -oid