Cytotrophoblast

The cytotrophoblast (or layer of Langhans) is the inner layer of the trophoblast, interior to the syncytiotrophoblast in an embryo. It serves to anchor the embryonic chorion to the maternal endometrium.

Cytotrophoblasts are stem cells in the chorionic villi. During differentiation, mononuclear cytotrophoblast fuse together into the multinucleated syncytiotrophoblasts.

Invading cytotrophoblasts
These cells invade maternal uterine tissues and thus are in direct contact with maternal stroma and immune cells.