FSH levels rise, recruitment of follicle. On day 7, one becomes dominant. As follicle grows it releases estradiol, causeing endometrium to mature. Estradiol stiumlates pituatary to release LH. 34 hrs after the surge the follicle bursts, forming corpus luteum. CL produces progesterone which maintains the endometrium. If fertilized, hCG will cause progesterone synthesis but if not, progesterone levels from CL decrease causing menses.