Allantois

Definition

The allantois is a membrane that develops from the yolk sac during early embryonic development in reptiles, birds, and mammals, including humans. It plays critical roles in gas exchange and waste removal for the developing embryo.

Related terms

Yolk sac: A membrane outside the embryo that provides early nutrition in the form of yolk in many vertebrates.

Amnion:

A thin membrane forming a closed sac around the embryo, providing protection and a stable environment.

Chorion:

The outermost fetal membrane in mammals, birds, and reptiles that contributes to the formation of the placenta in mammals