The ovarian surface is largely covered by peritoneum except at the attached border where nerves and vessels enter. The relationship between ovarian cortical and medullary areas is unusual in the mare (see F igure 1-4) . The ovary of the mare is “inside-out” compared with those of other farm animal species. In other words, the medullary or vascular zone is superfi cial and the
cortical zone (which contains the follicles) is in the inte- rior of the gland. The cortical tissue reaches the surface only at the depression of the ventral or free border. This, therefore, is the only area from which normal ovulation occurs and is appropriately termed the ovulation fossa. The ovulation fossa is covered by a layer of short polygonal cells, which are a remnant of the primitive germinal epithelium. The ovulation papilla of the cor- pus luteum does not project from the convex surface of the ovary as it does in other species but rather protrudes into the ovulation fossa. The ovary has both exocrine and endocrine func tions. The exocrine function is development of gametes, and the endocrine function is production of hormones.