Where Is the Cytotrophoblastic Shell?

The cytotrophoblastic shell is the external layer of cytotrophoblasts from the fetus that is found on the maternal surface of the placenta. The cytotrophoblastic shell firmly secures the placenta to the mother's endometrium called the decidua basalis.

What is the role of the cytotrophoblast?

The primary function of an interstitial cytotrophoblast is to anchor the growing fetus to the maternal uterine tissue. These cells may invade the whole endometrium and the proximal third of the myometrium.

What does the cytotrophoblast form?

The cytotrophoblast is a layer of mononucleated cells, which invades the syncytiotrophoblast matrix and forms early chorionic villi. Oxygen exchange occurs between the villi and the lacunae, and oxygen also diffuses into the extraembryonic tissue. The bilaminar embryo forms adjacent to the secondary yolk sac.