Ovary Anatomy

The ovaries are the female pelvic reproductive organs that house the ova and are also responsible for the production of sex hormones. They are paired organs located on either side of the uterus within the broad ligament below the uterine (fallopian) tubes. The ovary is within the ovarian fossa, a space that is bound by the external iliac vessels, obliterated umbilical artery, and the ureter. The ovaries are responsible for housing and releasing ova, or eggs, necessary for reproduction. At birth, a female has approximately 1-2 million eggs, but only 300 of these eggs will ever become mature and be released for the purpose of fertilization.

Anatomy of the ovaries is displayed in the images below.

The ovaries are small, oval-shaped, and grayish in color, with an uneven surface. The actual size of an ovary depends on a woman’s age and hormonal status; the ovaries, covered by a modified peritoneum, are approximately 3-5 cm in length during childbearing years and become much smaller and then atrophic once menopause occurs. A cross-section of the ovary reveals many cystic structures that vary in size. These structures represent ovarian follicles at different stages of development and degeneration. ^{[1, 2, 3]}

The Female Cycle

Each month, the ovaries go through a series of stages, depending on stimulation by the anterior pituitary hormones the follicle stimulating hormone (FSH) and the luteinizing hormone (LH). A typical female cycle lasts 28 days; however, this can range from 21-35 days.

The ovarian cycle has 2 distinct phases: the follicular phase (days 1-14) and the luteal phase (days 14-28). The follicular phase is characterized by follicle development and growth, the goal being that one follicle matures and releases an egg at the time of ovulation, around day 14 of the female cycle. The remaining immature follicles go through stages of degeneration up until day 28, when the cycle repeats itself. The egg that is released is picked up by the fimbriae of the uterine tube, and the egg is transported toward the uterus. If fertilization does not occur, the egg degenerates, and menstruation occurs.

Ovarian Ligament

Several paired ligaments support the ovaries. The ovarian ligament connects the uterus and ovary. The posterior portion of the broad ligament forms the mesovarium, which supports the ovary and houses its arterial and venous supply. The suspensory ligament of the ovary (infundibular pelvic ligament) attaches the ovary to the pelvic sidewall. This larger structure also contains the ovarian artery and vein, as well as nerve supply to the ovary.

Blood Supply, Nerve Supply, and Lymph Drainage

Blood supply to the ovary is via the ovarian artery; both the right and left arteries originate directly from the descending aorta. The ovarian artery and vein enter and exit the ovary at the hilum. The left ovarian vein drains into the left renal vein, and the right ovarian vein empties directly into the inferior vena cava.

Nerve supply to the ovaries runs with the vasculature via the suspensory ligament of the ovary, entering the ovary at the hilum. Supply is through the ovarian, hypogastric, and aortic plexuses.

Lymph drainage of the ovary is primarily to the lateral aortic nodes; however, the iliac nodes are also involved.

Cortex and Medulla

Histologically, the ovary has 2 main sections: the outer cortex and inner medulla. A germinal layer coats the entire ovary, made of cuboidal epithelial cells.

The cortex is where the follicles and oocytes are found at various stages of development and degeneration. The cortex is made of tightly packed connective tissue. The stroma of this cortical connective tissue is composed of spindle-shaped fibroblasts that respond to hormonal stimulation in a way different from that of other fibroblasts in the body.

The medulla is where the ovarian vasculature is found and is primarily loose stromal tissue. ^[4]

Ovarian Follicles

The ovarian follicles are found within the stroma of the ovarian cortex. A follicle consists of an oocyte surrounded by follicular cells called granulosa cells. Follicles go through stages of development each month, with the goal of their maturation to release the oocyte for the purpose of fertilization and reproduction. If the follicle fails to release the egg, it goes through degeneration.

Turner Syndrome

Turner syndrome is a chromosomal anomaly that characterized by the 45,X karyotype and occurs sporadically via paternal nondisjunction. Many mosaics of this syndrome exist, but typical manifestations include absence or dysfunction of the ovaries with presence of the uterus, cervix, and vagina. Primary amenorrhea occurs, with absence of breast development. Typical diagnosis is made prior to puberty. The common physical characteristics of Turner syndrome include short stature, webbing of the neck, swelling of the hands and feet, short fourth metacarpal, and cubitus valgus. Cardiac abnormalities, such as coarctation of the aorta, and renal abnormalities are common.

Ovarian Cysts

An ovarian cyst is the enlargement of either ovary beyond 5 cm in size, which is considered abnormal. Many different types of ovarian cysts exist, each classified as benign or malignant. The most common benign ovarian cysts in a premenopausal female are functional cysts, which are typically simple, clear, and nonseptated. The most common malignant ovarian cysts are epithelial carcinomas. The presence of an ovarian cyst can be detected on bimanual examination, and the diagnosis can be confirmed by ultrasound evaluation.

Ovarian Torsion

Ovarian torsion is an ovarian cyst that has grown in size to the point at which it turns over on itself, twisting the suspensory ligament of the ovary and cutting off blood supply. The typical presentation of a woman with ovarian torsion is intense, severe, sudden-onset pain in the right or left lower quadrant. Ultrasound evaluation reveals decreased or absent Doppler flow to the ovary on the affected side. The diagnosis of ovarian torsion warrants emergency surgery to reverse the torsion, hopefully in time to avoid necrosis of the tissue.

Ovarian Cancer

Ovarian cancer is detected physically in the same manner as an ovarian cyst, by bimanual or pelvic examination. Confirmation is then obtained by ultrasound and further workup as necessary.

Suspicion of an ovarian carcinoma on ultrasound examination includes characteristics such as complex, multiloculated, septated masses. The tumor marker CA-125 may be tested serologically, and an elevated level may support the diagnosis of ovarian cancer. This tumor marker is not always helpful, as it can be elevated in noncancerous conditions such as endometriosis, peritonitis, pregnancy, and liver disease. Ovarian cancer is an aggressive disease that is often not detected until late stages.

Other variants include the following:

• Surgical absence
• Ovarian transposition (oophoropexy)
• Postradiation changes
• Changes due to metastatic disease
• Variations secondary to transgender procedures