Chorionic Villi with Placental Hypoplasia

The structure and proliferation of endothelial and muscle cells of the chorionic veins of the underdeveloped placenta were studied. Histological, histochemical, and morphometric studies of the fetal membrane of the placenta of 36 placentas of 280-300 g at 39-40 weeks of pregnancy were carried out in comparison with 15 placentas of 450-500 g. The Ki-67 proliferation marker (Ventana, USA) was studied immunohistochemically with the determination of the proliferation index on the Roche Benchmark XT Ventana (USA) immunohistostainer by counting 1000 nuclei of endothelial cells and myocytes in capillaries, venules, and veins of the stem, intermediate and terminal villi. The outer and inner diameters of the veins were measured. The data were processed using the variation statistics method. The stem villi are supplied with a vein, artery, and capillaries. Amygdaloid veins are present at the bases, venules are on the surface of the intermediate villi. Capillaries are distinguished in the terminal villi. In hypoplasia, sphincter-like and valve-like structures are formed in the veins. Subendothelial sphincter rings of circularly located myocytes protrude into the lumen. Intimal cushions are obturator longitudinal layers of myocytes. Between the sphincters, the veins are dilated. Valvelike elements with myocytes and collagen fibers are found in small veins. These formations ensure blood distribution in the underdeveloped placenta and a decrease in trophic and oxygen starvation of the fetus. Hypoplasia is accompanied by venodilation with an increase in the external and internal diameters and an increase in the proliferation of cells of the chorionic veins.