A MENSTRUAL CYCLE Here are important events during the menstrual cycle: 1. The pituitary gland controls and starts the cycle. 2. The pituitary gland releases hormones that cause the egg in the ovary to mature. The luteinizing hormone (LH) initiates the maturation of the follicles. converts ruptured folicies into corpus luteum and causes the secretion of progesterone. The follicle stimulating hormone (FSH) assists in the maturation of the follicles and causes the secretion of estrogen from the follicles. 3. Meanwhile, the ovary itselt releases a hormone called estrogen, which causes the uterine lining to increase in thickness. The uterine ning becomes thicker so that the fertilized egg can attach to it. 4. The ovary releases an egg on day 14. Assume that no sperm is present 5. The egg moves through the oviduct and enters the uterus. 6. Meanwhile the uterine lining continues to thicken. 7. The egg has not been fertilized, therefore. It will not attach to the uterus. 8. The thick uterine ining is no longer necessary, so the cells of the thickened uterine lining break off and leave the vagina. The unfertilized egg is lost and some blood is lost too. This loss of cells from the uterine Ining blood, ond egg is called menstruation. 9. After menstruation, the cycle starts again.​