Summary of the Events of the Menstrual Cycle

Days 1-5 Menstrual Phase

Superficial layer of the uterus is removed

Bleeding occurs for three to five days Average blood loss is 50-150 mL By day 5 growing ovarian follicles

begin to produce estrogen and the removal of the uterine lining ceases

Days 6-14 Proliferate Phase Rising levels of estrogen produced by the

developing follicles stimulates the regeneration of the functional layer of the uterus

Glands form in the new layer and the blood supply to the layer increases

Ovulation occurs at the end of this phase (Day 12-14) due to the surge of LH in the blood

For the next 7 days the individual will be at their peak chance for conception

Days 15-28 Secretory Phase The corpus luteum of the ovary begins to

produce lots of progesterone This increases the blood supply to the

endometrium Progesterone also causes the endometrial

glands to swell up and they begin to secrete nutrients into the uterine cavity

If a fertilized egg should implant itself, these nutrients would sustain its early developmental stages

Days 15-28 Cont. The fertilized egg would also produce

hormones similar to LH so that the corpus luteum keeps on producing its hormones to sustain it

If the egg is not fertilized, the corpus luteum will degenerate as LH levels fall

Lack of ovarian hormones in the blood also causes the blood vessels that supply the endometrium to spasm (cramps) and twist

This cuts off the supply of blood and leads to cell death

Once this happens, the menstrual period will begin again