The ovary is an organ made up of two glands, known as the ovaries, which together with the uterus, the fallopian tubes (also called "uterine tubes" or "fallopian tubes"), the vagina and the vulva comprise the female reproductive tract.

What is the ovary?

The ovaries (or female gonads) are two almond-shaped glands each located on either side of the uterus. In adult women the ovaries are approximately 4 cm long, 2 cm wide and 1 cm thick each. They are connected through ligaments to the uterus and the fallopian tubes, but still they retain some autonomy in mobility.

The ovary does not always retain the same size throughout life: in girls it is smaller and the size also tends to decrease with old age. In women who have given birth to many children it is often larger than usual. 

Each of the two ovaries has two poles: an upper pole (or tubal), which joins the infundibulum to the uterine tube; a lower pole (or uterine), which is thinner and joins the uterus through the utero-ovarian ligament.

There are two layers of tissue that make up the ovaries: the innermost layer, or the medullary part, is rich of dense connective tissue and blood vessels for the spraying and the nourishment of the organ; the outer layer of tissue, the cortical part, which occupies about two-thirds of the entire gland, contains all the ovarian follicles at various stages of maturity every month during the menstrual cycle and it can stimulate the maturation of an oocyte and the subsequent expulsion of an egg, which is essential for reproduction.

What function does the ovary serve?

The ovaries play a dual role: besides producing eggs, indispensable elements for reproduction (gametogenica), they also secrete sex hormones (estrogen, progesterone and a small amount of androgens) that regulate all stages of the female reproductive system (endocrine function).

Each month the ovary releases an egg that has matured and therefore it is ready to be fertilized. When expelled from the ovarian follicle, the egg migrates to the fallopian tube (or uterine tube); following the release of the egg, the follicle becomes the corpus luteum and begins to secrete oestrogen and progesterone until the fertilization of the egg itself. 

This is recognized as the ovulation process that is stimulated by the hypothalamus, which signals the pituitary gland to produce follicle-stimulating hormones (FSH) in order to stimulate the ovarian follicles to produce oestrogen. In the meantime, the pituitary gland begins to release a luteinizing hormone (LH) in order to facilitate the egg’s release into the fallopian tube.

At the end of the menstrual cycle, if fertilization did not occur, the corpus luteum regresses and the egg is eliminated with the menstrual flow. If, however, the egg is fertilized, the egg passes from the tube to the uterus where it will implant and establish a pregnancy.

There are approximately 1 to 2 million eggs present at birth. However, only around 300 to 500 of these will be ovulated and become sufficiently mature to be released for fertilization. The remaining eggs gradually die off and eventually become depleted at menopause.