Abstract
A minute extravasated blood spot appeared in a space between the base of chorionic stem villi and caruncular septa as early as the 76th day of gestation, increased in number and size with the progress of gestation, and developed to the hematoma after 150 days of gestation. Epithelial layer of the caruncular septal tissue facing the arcade zone contained a large quantity of lipid droplets and showed signs of degeneration. Degenerative products are assumed to be absorbed by the trophoblast as a histotrophe. In addition, the trophoblast layer of the chorion facing the hematoma showed a distinct erythrophagocytosis of extravasated blood cells with the progress of gestation. Trophoblast cells lining an arcade zone were high columnar and showed well developed organelles suitable for strong phagocytosis. The activity of acid phosphatase was detected only in the trophoblast of the arcade zone. Processes of the ingestion and digestion of erythrocytes were almost similar to those described by earlier authors in other types of placentae. Intercellular space being developed particularly in a basal zone of the trophoblast seemed to be the important channel to transport the digested material. Erythrophagocytizing trophoblast layers often invaginated into the mesenchyme. Trophoblast cells of these invaginated layers usually contained abundant hematogenous pigment in a basal zone. These facts suggest that the intracellular digestion of erythrocytes requires a long time.
