The main female reproductive organs which produce the ova (egg cells – see OVUM) and steroid HORMONES in a regular cycle (see MENSTRUATION) in response to hormones (see GONADOTROPHINS) from the anterior PITUITARY GLAND. Situated one on each side of the uterus in the lower abdomen, each ovary contains numerous follicles within which the ova develop. Only a small proportion of these reach maturity, when the ovum is described as a Graafian follicle. OVULATION occurs and, if the ovum is fertilised, a pregnancy may develop. (See also ENDOCRINE GLANDS; OESTRADIOL; OESTROGENS; PROGESTERONE.)