In placental mammals, the chorion and the allantois together form the fetal side of the mature placenta. This is a chorioallantoic placenta. Chorion forms part of fetal tissue, allantois becomes ...
The fetal membranes consist of the chorion, amnion, yolk sac, and allantois. The chorion has three layers: cytotrophoblastic, chorionic connective tissue, and basement membrane. The chorion lies ...
Synapsids were mammals that evolved from amniotes, a clade of tetrapod vertebrates that have an amnion for the protection of the embryo, a chorion for gas exchange, and an allantois for metabolic ...