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Lobular structure of hemochorial primate placentas, and its relation to maternal vessels

1973; Wiley; Volume: 136; Issue: 2 Linguagem: Inglês

10.1002/aja.1001360203

1553-0795

Peter Gruenwald,

Fetal and Pediatric Neurological Disorders

Abstract Structure of the placental lobule and its topographic relation to the ostia of maternal vessels were studied in primates with hemochorial placentas. The lobule contains most of the terminal villi, whereas stems predominate in interlobular areas. The placenta of Tarsiidae consists of one lobule supplied by one maternal artery. Ceboidea (New World Monkeys) have multilobular placentas. In both forms arteries reach the intervillous space below the center of a lobule, and then continue into the lobule as perforated, branched channels which lose their maternal vessel wall. In Cercopithecoidea (Old World Monkeys) each maternal artery has a convolution in the decidua below an interlobular area, then continues straight to a point below the center of a lobule, and opens there. Hominoid (ape and human) placentas are supplied by much larger numbers of arterial convolutions at interlobular areas, with interlobular openings close to anchoring points of villous stems. Venous drainage is at the periphery in Tarsius and interlobular in all other forms. The interlobular intervillous space may have more or less specialized portions emptying into maternal veins. Circulation in the intervillous space must be directed from the center toward the periphery of the lobule in Tarsiidae and Ceboidea . In Cercopithecoidea and Hominoidea the path of maternal blood issuing from arteries is not known. It is suggested that arterial blood irrigates first the periphery, and that this is the cause of dense proliferation of villi there.