In zoology, the female reproductive organ (see egg s and sex hormones ( estrogen and progesterone ).
Human females have two ovaries, almond-shaped organs about 1.5 in. (4 cm) long. They contain hollow balls of cells (follicles) that hold immature eggs. About 150,000–500,000 follicles usually are present at birth; by young adulthood, only about 34,000 remain. The number continues to decrease until menopause , when the few remaining follicles decay and the ovaries shrink and produce far less estrogen. Only 300–400 follicles mature and release an egg, which develops into an embryo if fertilized or, if not, passes from the body with menstruation . In botany, an ovary is the enlarged base of a flower's female organ (pistil). It contains ovules, which develop into seeds when fertilized, and matures into a fruit.