Surface structure of the human term placenta and of the uterine wall post partum in the screen scan electron microscope

Abstract

The human term placenta after normal and toxemic pregnancies, the membranes, and the endometrial surface post partum was examined by means of the screen scan electron microscope. This method permits a stereoscopic view on tissue surfaces with magnifications up to ×20,000. Anatomical relations between maternal erythrocytes and the syncytiotrophoblastic surface of the tertiary chrionic villi can thereby be visualized. The villous surface of the mature human placenta consists of a relatively flat brush border of microvilli. In the region of infarctions the terminal chrionic villi are covered by a dense fibrin network, and maternal erythrocytes there are fixed by fibrin very similar to intravascular clot formation. Placental septa are wrapped by a trophoblastic layer where single chorionic villi insert. The paraplacental exchange surface of the membranes is stabilized by coarse collagen fibrils, and the coverture of the amnion cells resembles rudimentary microvilli. Cytotrophoblastic cells near the vessel entries in the basal plate are linked like cells in an epithelial layer. Postpartum hemostasis in utero is partially managed by a clotting process, the result of which can be demonstrated as a fibrinous “wallpaper” extended on the internal surface of the uterus.