Figure 1.

An illustration of the anatomy and morphology of the non-human primate placenta showing both the maternal and fetal surfaces along with a cross-sectional view. Major structures including primary and secondary placental lobes, bridging vessels, umbilical arteries, umbilical vein, cotyledons, lobules, villous tree, spiral arteries, and endometrial veins are identified. Panel (a) shows a photograph of the fetal side of a rhesus macaque placenta after Caesarean delivery, with primary placental lobe, secondary placental lobe, umbilical cord, and bridging artery and veins indicated. Panel (b) is a schematic illustration of the maternal side of the placenta, with anatomic cotyledons (green dashed lines) and functional lobules (blue dashed lines) indicated in both primary and secondary lobes. Panel (c) is a schematic cross-section of the placenta, with the cotyledon and the lobule indicated as in panel (b). Vessels carrying oxygenated blood are shown in red (with red arrows indicating flow direction), and vessels carrying deoxygenated blood are shown in blue (with corresponding flow indicated by blue arrows). Oxygen, nutrients, and wastes are exchanged between the maternal blood occupying the intervillous space and the fetal capillaries comprising the villous tree, as indicated by the double-headed white arrows.