During first half of menstrual cycle, FSH from anterior pituitary stimulates growth of ovarian follicles, growing ovarian follicles secrete increasing levels of estrogen, precipitating a surge of LH from anterior pituitary on day 14, which causes ovulation, edema and collagenases weaken the ovarian follicular wall, leading to rupture of ovarian surface, at ovulation the oocyte and corona radiata are expelled from ovary