[Lightmicroscopical and histochemical studies on the chorionic plate of the mature human placenta (author's transl)].

The chorionic plate of the normal mature human placenta was studied by light-microscopy and enzyme-histochemistry. Thereby the following findings were obtained in the various layers: The enzyme content of the amniotic epithelium refers to a secretory activity. The question with regard to a resorbant activity remains unclarified. The cells of the amnion mesoderm chiefly show the enzymes of the intermediary metabolism. The intermediate layer consists of mesothelium cells which furthermore have also phagocytotic activity. The chorionic plate mesoderm consists of several layers with connective tissue cells of diverse stage of differentiation. In the early embryonic phase they differentiate amnionward from the primary cytotrophoblast layer and still get cellular supply from residual primary cytotrophoblastic cells up to the date of birth. The enzymes of the primary cytotrophoblast cells refer accordingly with a strong activity of G6PDH to proliferation and differentiation. One part of the X-cells embedded in the Langhans fibrinoid stria descends from this primary cytotrophoblast layer; but in part they differentiate also from the Langhans cells of the placental villi surrounded by the fibrinoid stria. According to their different descent, these cells show a varying content of enzymes. The bordering of the chorionic plate to the intervillous space is represented by a rudimentary, syncytotrophoblast layer.