1 example sentence using allantois.
Allantois used in a sentence
Allantois in a sentence as a noun
The umbilical cord develops from and contains remnants of the yolk sac and allantois. It forms by the fifth week of development, replacing the yolk sac as the source of nutrients for the embryo" per wiki.
Allantois definitions
noun
the vascular fetal membrane that lies below the chorion and develops from the hindgut in many embryonic higher vertebrates (reptiles, birds and mammals)