Ovary << OH vuhr ee >> is either of a pair of female sex organs that store and release eggs. The ovaries also secrete estrogens and progesterone, the female sex hormones. The human ovary is oval in shape and about the size of an unshelled walnut. One ovary is located on each side of the uterus, at the base of the abdomen.
At birth, each ovary contains about 400,000 immature eggs. About 400 of these eggs will mature and be released during a woman’s childbearing years. During the first half of each menstrual cycle, one of the eggs matures. Also during this time, the ovaries release estrogens, which cause the lining of the uterus to thicken in preparation for pregnancy. Ovulation (the release of the mature egg) occurs about midway through the menstrual cycle.
After ovulation, the ovary that released the egg secretes progesterone, which maintains the uterine lining, as well as estrogens. If the egg is fertilized, a pregnancy begins. The ovary and placenta–an organ that develops early in pregnancy–secrete progesterone and other hormones, and the menstrual cycle stops until after the baby has been born. If the egg is not fertilized, the ovary stops producing progesterone about 14 days after ovulation. The egg and the uterine lining then pass out of the body during menstruation.
Between the ages of 45 and 55, most women stop menstruating and enter a period called menopause. The ovaries gradually stop functioning and shrink to about the size of a pea.
