ANATOMY

Detailed explanation-1: -allantois, an extra-embryonic membrane of reptiles, birds, and mammals arising as a pouch, or sac, from the hindgut. In reptiles and birds it expands greatly between two other membranes, the amnion and chorion, to serve as a temporary respiratory organ while its cavity stores fetal excretions.

Detailed explanation-2: -The allantois is also known as allantoic. It is present in all embryos and extra-embryonic tissues. It helps the embryo exchange gas and helps in disposing of the liquid waste. The allantois, along with the amniotic membrane and chorionic membrane help in the development of the embryo.

Detailed explanation-3: -The function of the allantois is to collect liquid waste from the embryo, as well as to exchange gases used by the embryo.

Detailed explanation-4: -The allantois arises as an endodermally lined ventral outpocketing of the hindgut (see Figure 1). In the human embryo, it is just a vestige of the large, saclike structure that is used by the embryos of many mammals, birds, and reptiles as a major respiratory organ and repository for urinary wastes.