In humans, cells called ovarian hilar cells are found in the hilum of the ovary in association with vascular spaces and nonmyelinated nerve fibers. These cells, which appear to be structurally related to the interstitial cells of the testis, contain Reinke crystalloids. The hilar cells appear to respond to hormonal changes during pregnancy and at the onset of menopause. Research suggests that the hilar cells secrete androgens; hyperplasia or tumors associated with these cells usually lead to masculinization.
Blood supply to the ovaries comes from two different sources: Ovarian and uterine arteries.
The ovarian arteries are the branches of the abdominal aorta that pass to the ovaries through the suspensory ligaments and provide the principal arterial supply to the ovaries and uterine tubes. These arteries anastomose with the second blood source to the ovary, the ovarian branches of the uterine arteries, which arise from the internal iliac arteries. Relatively large vessels arising from this region of anastomosis pass through the mesovarium and enter the hilum of the ovary. These large arteries are called spiral arteries because they branch and become highly coiled as they pass into the ovarian medulla (see Fig. 23.2).
Veins accompany the arteries and form a plexus called the pampiniform plexus as they emerge from the hilum. The ovarian vein is formed from the plexus.
In the cortical region of the ovary, networks of lymphatic vessels in the thecal layers surround the large developing and atretic follicles and corpora lutea. The lymphatic vessels follow the course of the ovarian arteries as they ascend to paraaortic lymph nodes in the lumbar region.
Ovaries are innervated by the autonomic ovarian plexus.
Autonomic nerve fibers that supply the ovary are conveyed mainly by the ovarian plexus. Although it is clear that the ovary receives both sympathetic and parasympathetic fibers, little is known about their actual distribution. Groups of parasympathetic ganglion cells are scattered in the medulla. Nerve fibers follow the arteries, supplying the smooth muscle in the walls of these vessels, as they pass into the medulla and cortex of the ovary. Nerve fibers associated with the follicles do not penetrate the basal lamina. Sensory nerve endings are scattered in the stroma. The sensory fibers convey impulses via the ovarian plexus and reach the dorsal root ganglia of the first lumbar spinal nerves. Therefore, ovarian pain is referred over the cutaneous distribution of these spinal nerves.
At ovulation, about 45% of women experience midcycle pain (“mittelschmerz”). It is usually described as a sharp, lower abdominal pain that lasts from a few minutes to as long as 24 hours and is frequently accompanied by a small amount of bleeding from the uterus. It is believed that this pain is related to smooth muscle cell contraction in the ovary as well as in its ligaments. These contractions are in response to an increased level of prostaglandin F2 mediated by the surge of LH.