Endometrium with eggcell (400X)

The two kinds of trophoblastic cells are now clearly seen. The layer closest to the centre of the villi is is the cytotrophoblast and consists of a distinct layer of separate cells with one nucleus each. In contrast, the outer layer consists of cells forming a syncytium; that is, many cells have fused to form one, multinucleated cell. This layer is therefore called the syncytiotrophoblast. The syncytiotrophoblast is made from the cytoptrophoblast.