Follicular phase: Between 7^th -14^th day of the menstrual cycle, the primary follicles in the ovary grow to become a fully mature Graafian follicle, and simultaneously the endometrium of uterus regenerates through proliferation (which are induced by changes in the levels of pituitary and ovarian hormones) 

• Luteal phase: Between 14^th -28^th day of the (menstrual) cycle, during which the remaining parts of the Graafian follicle transform as the corpus luteum, the corpus luteum secretes large amounts of progesterone which is essential for maintenance of the endometrium (Such an endometrium is necessary for implantation of the fertilised ovum and other events of pregnancy) 
• The secretion of gonadotropins (LH and FSH) increases during the follicular phase, and stimulates follicular development as well as secretion of estrogens by the growing follicles, both LH and FSH attain a peak level in the middle of cycle (about 14^th day), rapid secretion of LH leading to (its maximum level during the mid-cycle called LH surge induces) rupture of Graafian follicle and thereby the release of ovum (ovulation)