In the female reproductive system, ova are produced in the ovaries, two small organs set in the pelvic cavity below and to either side of the bellybutton. The ovaries also secrete the hormones estrogen and progesterone. The estrogen hormone causes the thickening of the lining of the uterus and vagina in the early phase of the menstrual cycle. The estrogen hormone is also responsible for female secondary sex characteristics such as pubic hair and breasts, and they affect other tissues including the genital organs, skin, hair, blood vessels, bone, and pelvic muscles. …
