Describe the control of the menstrual cycle by the hormones FSH, LH, Oestrogen and Progesterone, in the situation where the person does not become pregnant. You may use a diagram to show how their levels change throughout the cycle.

Day 1-5: FSH is released from the pituitary gland and stimulates the primary oocytes to complete meiosis 1 and mature. The primary oocyte is inside a primary follicle which matures into a Graafian follicle. FSH also stimulates the outer layer of the Graafian follicle to release Oestrogen.Day 5-12: Oestrogen has 3 functions:- it causes the thickening of the endometrium (lining of the uterus)-it inhibits FSH production-it stimulates LH production from the pituitary glandDay 12-14: Oestrogen leads to low levels of FSH which indirectly inhibits Oestrogen so levels of Oestrogen drop.LH is released and a peak around day 14 stimulates ovulation (the release of the mature secondary oocyte from the Graafian follicle).LH levels then drop since there is no longer as much Oestrogen to stimulate it. Day 15-28: The Graafian follicle turns into another structure called the Corpus Luteum once it has released the oocyte. The Corpus Luteum produces progesterone which maintains the lining of the endometrium.In the situation where the person does not become pregnant, the Corpus Luteum degenerates. The levels of all the hormones fall, the endometrium breaks down and a menstrual period happens.