[Maternal blood flow in the human placenta (author's transl)].

The intervillous microcirculation in the human placenta is still a subject of debate. This paper aims to establish whether or not a division of the human placenta into flow units - the "placentons" of Schuhmann et al. (1971, 1976) - is morphologically conceivable, and what pathways exist for the maternal blood flow through the intervillous space. The findings are compared with flow models published in the literature, and are discussed. Spiral arterial punctures were performed in 22 fresh placentas from term births using Wigglesworth's procedure, and the intervillous space was filled with Microfil. In five other placentas the fetal villi were also contrasted with Micropaque and gelatine. Six control placentas, which were not filled with contrast medium, served to eliminate the possibility of filling artefacts. Plain radiographs in choriobasal projection, lateral films of the lamillarly dissected injection regions and histologic serial sections documented the pathways followed by the contrast medium. The human placenta can be divided into flow units: each fetal cotyledon can be shown to be supplied by a maternal spiral artery. Within the flow units, flow is routed through arterial, capillary and venous areas can be clearly identified. They were also demonstrated in the control placentas, which were not filled with contrast medium.