The umbilical cord inserts into the chorionic plate (has an eccentric attachment).

Infiltration of the chorionic plate by neutrophils is diagnostic of (mild) chorioamnionitis.

The extraembryonic coelemic cavity is also called the chorionic cavity, and is enclosed by the chorionic plate, which is composed of an inner layer of somatopleuric mesoderm and an outer layer of trophoblast cells.

Blood in the maternal circulation is delivered via open ended arterioles to the intervillous space of the chorionic plate, where it bathes the chorionic villi that carry umbilical capillary beds, thereby allowing gas exchange to occur between the maternal and fetal circulation.

Cytotrophoblastic cells penetrate into the overlying syncytium until they reach the maternal endometrium, and form a thin outer cytotrophoblastic shell that serves to unite the endometrium through the chorionic sac stem or anchoring villi that are directed from the chorionic plate to the decidua basalis.