[cells lining the outside of the blastocyst; after binding to the endometrium, trophoblasts develop into two distinct layers, an inner layer of mononuclear cytotrophoblasts and an outer layer of continuous multinuclear cytoplasm, the syncytiotrophoblasts, which form the early fetal-maternal interface. ( CSP )]
UMLS (CSP) C0041178 Relation/PAR: embryo/fetus membrane