The junctional pattern of the human villous trophoblast. A freeze-fracture study.

This investigation of the junctional pattern of the human trophoblastic epithelium was carried out on the fractured faces of (a) the syncytial plasma membrane bathed by the maternal blood (S-PMm); (b) by syncytial plasma membrane in contact with either the cytotrophoblast or the trophoblastic basement membrane (S-PMf), and (c) the cytotrophoblastic plasma membrane (C-PM). The most relevant findings were tight junctions on the SPMm, and the intertrophoblastic junctional pattern, not realizing a tight subcompartmentalization between syncytium and cytotrophoblast. The following aspects were discussed: the SPMf represents the last membrane barrier before the fetal capillary, and the function of the cytotrophoblast seems to be limited to the modulation of syncytial activity.