Discoidal placenta

The discoidal deciduate placenta occurs in chiropterus, insectivores, primates and man. It develops on the entire surface of the blastocyst which in turn is pushed away from the uterine wall into the cavity of the uterus.

The blastodermic vesicle is enclosed in the uterine tissue and a thin layer of endometrium is pushed away into the uterine cavity from the expanding blastodermic pit. The part of uterine tissue that encloses the blastocyst is called as the decidua capsularis.

At a later stage, the chorionic villi disappear on its free side but they become more confined to the side which is attached to the uterine wall.

The part of uterine mucosa which embeds the part of uterine wall is called the decidua basalis. The remaining part of maternal tissue is called the decidua parietalis.

Discoidal placenta