Radioangiographic measurement of the internal diameters of the uteroplacental arteries in rhesus monkeys

The internal diameters of successive anatomic segments of the uteroplacental arteries in Macaca mulatta were measured at 100 to 150 days’ gestation. Although the absolute values vary widely, the proportional relationships between segments are uniform from animal to animal and from one time in gestation to another. We also observed that each of the two uterine arteries supplies a restricted portion of the placenta with little overlap, that there is predominance of one uterine artery over the other in the number of placental lobes supplied, and that two radial arteries occasionally contribute to a single spiral artery, giving rise to an anastomotic loop.