The giant cells in the placenta of the rabbit

Abstract

Of the 2 kinds of giant cells found, the larger are derived from the fetal tropho-blast, cells of which become detached about the 7th day of gestation and penetrate into the obplacental mucosa. These cells grow rapidly and may attain a length up to 0.4 mm.; they persist until about the 22nd day. Large numbers of these cells are also formed from that portion of the trophoblast of the proximal zone of the bilaminar omphalopleure, which projects free into the uterine cavity after the attachment of the blasto-cyst to the placental folds on the 8th day and the disappearance of the remainder of the omphalopleure. The cells proliferated off from this "trophoblastic fringe" pass into the uterine cavity, penetrate the regenerated uterine epithelium of the antimesometrial uterine wall and enter the underlying tissues. This proliferation continues until the 16th day. The smaller mesometrial giant cells are of maternal origin, being formed by the proliferation of the endothelial lining of the capillaries in the deep placental region. They appear at about the 11th day and persist until after the 27th. The trophoblast of the chorion laeve gives origin to great numbers of multinucleate spheres which become free in the uterine cavity and in the inter-placental furrow. These bodies are inactive degenerate structures.