Characteristic patterns of maternal and fetal arterial construction in the rabbit placenta.

We studied vascular structure of the rabbit placenta, especially on three-dimensional morphological patterns and developmental process. Basic structure of maternal arterial system was re-constructed during day 13-18 of pregnancy, forming main routes for blood supply through the arterial sinuses and radial arteries. Intra-villous spaces were drastically developed showing as branches from the terminal radial arteries. Fetal arterial system was generated accompanied with maternal vascular development, showing characteristic features such as the perforating linear artery, hairpin flexion, and circular anastomoses in the capillaries. From the correlation of maternal and fetal blood currents, gas-exchange style in the rabbit placenta was considered as counter-current and pool mixed patterns. These data demonstrated an original feature for the placental arterial systems in rabbits, which differed from other animals having a property for discoid placenta.