The proliferative (Follicular) phase
Under the influence of estrogen from the developing follicle, the endometrium increasers rapidly in thickness from the 5th to the 14th days of the menstrual cycle.
The secretory (luteal) phase
After ovulation the corpus luteum secretes large amounts of progesterone and estrogen. The endometrium become more highly vascularise, hyperaemic and slightly edematous.