Figure 2. Vascular development of maternal caruncle (CAR) and fetal cotyledon (COT) throughout the last two-thirds of gestation in sheep.

Capillary area density (capillary area as a proportion of total tissue area) of both maternal (caruncle) and fetal (cotyledon) placental tissues increased exponentially from day 50 through day 140 after mating. Capillary area density is a commonly used measure of angiogenesis, and based on stereological principles also is equivalent to capillary volume density (capillary volume as a proportion of total tissue volume; Weibel, 1972; Hudlicka, 1984). Figure taken from Reynolds et al. (2005b).