Light and electron microscopic investigations on the chorionic plate of the human placenta at term (author's transl)]

The chorionic plate of the human placenta at term consists of amniotic epithelium, amniotic connective tissue, intermediate layer, chorionic connective tissue, cytotrophoblast, and syncytiotrophoblast. - The connective tissue layers are divided into unorientated (situated just below the amniotic epithelium and in direct contact with the trophoblast) and orientated layers (between the two unorientated connective tissue layers). Besides an accelular border below the amniotic epithelium the connective tissue includes fibrocytes, fibroblasts, histiocytes, and old Hofbauer cells in the intermediate layer. - From the edge of the chorionic plate to its centre, the number of well preserved cytotrophoblasts decreases; instead of them especially intercellular substances (subchorial fibrinoid) but also degenerating cells predominate. In the trophoblast layer rests of chorionic villi are localized. Among the intact cytotrophoblasts 4 types can be distinguished (less differentiated, well differentiated, spongiotrophoblast-like, and glycogen-rich cytotrophoblastic cells). They are interpreted as different developmental stages of one and the same cell population. - The syncytiotrophoblast is inter rupted at many places; only fragments can be observed. Then cytotrophoblastic cells or intercellular substances may form the border to the intervillous space.