Notes on the morphology of the chimpanzee and orang-utan placenta

The placentae of 11 chimpanzees and five orang-utans were collected from Japanese zoos immediately after delivery and were examined according to the methods routinely used for the human placenta. Placenta extrachorialis (circumvallate and circummarginate placenta) occurred in 80 per cent of the specimens collected from each species. In both groups, the placental vessels were distributed predominantly in the magistral pattern, and the umbilical cord was eccentrically inserted. Subchorionic fibrin, sometimes marked, was seen in all 16 placentae, and there was a high incidence of small intervillous thrombi and deposits of intervillous fibrin. These observations, together with the histological and ultrastructural findings, confirm the previously reported similarity between the placentae of the great apes and the human placentae.