A sparsely vascularised zone in the cortex of the bovine ovary

We consider that the microvascular bed may play a role in the initiation and maintenance of growth from primordial to primary follicles. Therefore, using immunochemistry, we examined microvessels in calf and cow ovaries to identify the presence of factor VIII-related antigen endothelial cells. A vessel-poor zone was observed in the cortex of immature and mature cow ovaries. Primordial and primary follicles were assembled in this zone. It is concluded that follicular dormancy is likely to be maintained by the scarcity of microvessels and thus by the consequent poverty of the blood supply.