Structure and Function of the Ovaries

The ovaries sit on either side of the uterus, along the peritoneum, in a shallow indentation called the ovarian fossa. They lie between the internal and external iliac vessels, the main blood supply for the abdominal organs and legs. The ovaries are they are somewhat mobile, so their location may change slightly depending on a variety of factors.

While the ovaries are attached, they have a fairly impressive range of movement. The suspensory ligament goes between the ovary and the side wall of the pelvis. The ovarian blood vessels also run along this ligament. Each ovary is also attached to the broad ligament of the uterus and to the side of the uterus with the ovarian ligament. Though these attachments remain, women who have been pregnant have especially mobile ovaries — they can even move behind the uterus.

It is possible for a physician to feel the ovaries on a routine exam, but this depends on their location and other factors, like whether the patient has other health issues or is obese. Ovaries with abnormalities like cysts may be easier to feel. Generally, an ultrasound is the most common method of assessing the ovaries for deformities or other conditions.

Normal ovaries are about three-quarters of an inch wide, one and a half inches long, and a half-inch thick. That said, the organs change in size as women age. Volumes peaks at around age 20, at about 7.7 milliliters, and slowly decreases to about 2.8 by menopause.

Ovaries have three layers. The outer layer consists of cuboidal epithelium, a type of tissue that lines most organs of the body. Under that is the tunica albuginea, a layer of connective tissue made of collagen. The innermost layer is the cortex and contains the ovarian follicles. Inside is a central zone of blood vessels and loose connective tissue called the medulla.

Ovarian follicles are made of a spherical collection of cells, each containing a single egg or oocyte. In each menstrual cycle, roughly 10 follicles begin to mature, with one becoming dominant. To ovulate, a follicle passes through multiple stages of maturation in a process called folliculogenesis before releasing an egg into the fallopian tube.

The ovaries' blood supply comes from both the ovarian artery and the uterine artery. The former branches off of the abdominal aorta and runs along the suspensory ligament into the broad ligament of the uterus. It can also attach to the uterine artery itself. The ovarian vein travels along the suspensory ligament. The left ovarian vein connects to the left renal vein, while the right ovarian vein goes directly into the inferior vena cava, the large vein that carries blood from the lower part of the body directly to the heart.

While most women have two ovaries, some developmental variants or abnormalities may occur. Cystic ovaries are the most common variant. Some occur naturally with hormone changes, while others persist and grow to a significant size. Accessory ovaries are rare but can develop when there are more than two attached to any of the connecting ligaments. An extremely rare occurrence is a supernumerary ovary, which connects to an organ other than the uterus, such as the bladder, rectum, or small intestine.

Because the ovaries are close to so many important organs, doctors must exercise extreme care when operating on the lower abdomen, particularly if maintaining fertility is important to the patient. High-risk surgeries include emergency cesarean sections, ruptured ectopic pregnancies, and ovarian torsion — when the ovary twists, cutting off its blood supply.

Functional ovaries are important for many reasons. When the ovaries are not working properly, women may have a very difficult time becoming pregnant and are likely to experience infertility. Ovarian failure leads to menopause, which reduces the benefit of estrogen and causes weakened bones. Problems with ovarian function can also lead to anemia, increased risk of heart disease, and pain.