During follicular phase of menstruation the primary follicles in the ovary grow to become the mature Graffian follicle. The increase in LH and FSH stimulates the follicular development as well as secretion of estrogens by the growing follicles. At midcycle there is an LH surge which causes the rupture of Graffian follicle to release the ovum. This is followed by the Luteal phase. In luteal phase that occurs after ovulation , formation of corpus luteum occurs that starts secreting the hormone progesterone that maintains the uterine endometrium and keeps it ready for implantation.
