Spatial Relationships between Serrated Granulosa and Vascularity of the Preovulatory Follicle and Developing Corpus Luteum

Color Doppler and B-mode film clips were taken of the preovulatory follicle an hour before the beginning of ovulation. Locations of serrated granulosa and color-flow signals were determined by clock-face positions with the apex of the follicle (future ovulation site) at 12 o'clock. Mares were divided into a group with normal follicle evacuation (completion within 1 hour; n = 21 mares) and a group with septated evacuation (n = 5). The septated group was characterized by completion of evacuation in ≥3 hours and formation of echoic trabeculae in the antrum during evacuation. The trabeculae in the septated evacuations contained blood-flow signals and were interpreted to be creases in the slowly collapsing follicle wall. In the normal-evacuation group, serration and blood-flow signals were located at the basal hemisphere of the follicle directly opposite to the apex, and the o'clock positions did not differ significantly between the two characteristics. The apical area was devoid of both serration and color-flow signals. Vascularization of the corpus luteum began at the basal third on the day of ovulation and reached the apical third in a mean of 5.5 days. In septated evacuation, color-flow signals were detected at every clock-face position in each mare at the hour before ovulation. Results supported the following hypotheses: (1) both granulosa serration and color-flow signals occur in a similar basal area opposite to the apex; and (2) prolonged septated follicle evacuation is associated with vascularization of a greater circumference of the follicle than for normal evacuation and includes the apical area.