Ovaries
From Encyclopedia of Sex and Sexuality
A woman’s internal organs, located on either side of the uterus. They are responsible for the monthly release of oocytes (ova) and the production of the female sex hormones, estrogen and progesterone. The ovaries are small, the size and shape of a large almond, but they determine much of a woman’s physiology. At puberty hormones from the ovaries stimulate the growth of secondary sexual characteristics, body hair, and the distribution of soft, fatty tissue in the body. Most important, the ovaries give a woman the ability to reproduce.
The ovaries respond to stimulation by “gonadotropins”—luteinizing hormone (LH) and follicle stimulating hormone (FSH)—secreted by the pituitary gland. Gonadotropins stimulate cells in the ovary to produce the sex hormones, control maturation of the follicle that contains the developing egg, and stimulate ovulation. These pituitary hormones also cause the ovary to initiate the female menstrual cycle, preparing the uterus each month to receive a fertilized egg.
The ovaries consist of two basic components; stroma, or cells that make up the bulk of the ovary, and follicles. The stroma contains blood vessels and nerves and helps support and encapsulate the ovary. The follicles are the structures that develop around the oocytes (eggs), providing nourishment and support to them. The follicle cells also secrete the female sex hormones.
The number of oocytes per ovary is determined during fetal development and does not change over the life of the woman. About 200,000 ova are present in each ovary when a female infant is born.
Hormonal changes during puberty stimulate the follicles that contain each egg to begin developing. The egg itself does not undergo any changes during follicular development, but the follicle surrounding the egg changes both in size and function.
