2. LE 46-9b Vagina Cervix Oviduct Ovaries Uterus Endometrium Follicles Corpus luteum Uterine wall

3. The Menstrual Cycle 4 phases –Phase 1: Follicular Phase –Phase 2: Ovulation –Phase 3: Luteal Phase –Phase 4: Menstruation

4. Menstrual Cycle Follicular Phase –Pituitary releases FSH, causing follicle to grow –Follicle release estrogen helping the endometrium to grow Causing the pituitary to release LH Ovulation –Excess LH causes follicle to burst, releasing the ovum during ovulation Luteal Phase –Shed follicle becomes the corpus luteum, which produces progesterone –Progesterone causes the endometrium to thicken Menstruation –If fertilization does not occur after 2 weeks, the corpus luteum dies, leading to menstruation.

5. Phase 1: Follicular Phase Anterior Pituitary secretes FSH –stimulates several follicles in the ovaries to grow –Eventually, one of these follicles gains the lead and dominates the others, which soon stop growing During all of this time, the follicle is releasing estrogen –Estrogen helps the uterine lining (endometrium) to grow and eventually causes the pituitary to release a very large amount of LH. –The endometrium is preparing for the implantation of a fertilized cell.

6. Phase 2: Ovulation The sudden surge of LH (luteal surge) in response to the increase in estrogen triggers ovulation Ovulation is the release of the follicle from the ovary The Luteal surge makes the follicle burst and release the ovum. The ovum them begins its journey into the fallopian tube, which is also known as the oviduct.

7. Phase 3: Luteal Phase The ovum has moved into the fallopian tube and the follicle has been ruptured and left behind in the ovary. The ruptured follicle (now a fluid filled sac) condenses into a little yellow blob called the corpus luteum.

8. Phase 3: The Luteal Phase The corpus luteum continues to secrete estrogen and now begins to secrete another hormone, progesterone –Progesterone promotes the growth of glands and blood vessels in the endometrium. –Without progesterone, a fertilized ovum cannot latch onto the uterus and develop into an embryo. –After about 13 to 15 days, if fertilization and implantation have not occurred, the corpus luteum shuts down. Once it has stopped producing estrogen and progesterone, the final phase of the menstrual cycle begins.

9. Copyright Pearson Prentice Hall Ovulation

10. Phase 4: Menstruation Once the corpus luteum turns off, the uterus can no longer maintain its thickened walls It starts to reabsorb most of the tissue that the progesterone encouraged it to grow Since too much to reabsorb, a certain amount is shed This sloughing off is known as menstruation or bleeding.

11. Copyright Pearson Prentice Hall

12. Menstrual Cycle Recap Follicular Phase –Pituitary releases FSH, causing follicle to grow –Follicle release estrogen helping the endometrium to grow Causing the pituitary to release LH Ovulation –Excess LH causes follicle to burst, releasing the ovum during ovulation Luteal Phase –Shed follicle becomes the corpus luteum, which produces progesterone –Progesterone causes the endometrium to thicken Menstruation –If fertilization does not occur after 2 weeks, the corpus luteum dies, leading to menstruation.

13. LE 46-13 Hypothalamus Anterior pituitary Control by hypothalamus Pituitary gonadotropins in blood FSHLH FSH LH GnRH Inhibited by combination of estrogen and progesterone Inhibited by low levels of estrogen Stimulated by high levels of estrogen LH surge triggers ovulation FSH and LH stimulate follicle to grow Mature follicle Growing follicle Ovarian cycle Corpus luteum Degenerating corpus luteum Follicular phase OvulationLuteal phase Progesterone and estrogen secreted by corpus luteum Estrogen secreted by growing follicle in increasing amounts Progesterone and estro- gen promote thickening of endometrium Peak causes LH surge Ovarian hormones in blood Estrogen level very low Progesterone Estrogen Endometrium Uterine (menstrual) cycle Menstrual flow phaseProliferative phaseSecretory phase Days 28 2520 1514 105 0

14. Websites for Menstruation http://www.tutorvista.com/content/biology/ biology-ii/reproduction/menstrual- cycle.phphttp://www.tutorvista.com/content/biology/ biology-ii/reproduction/menstrual- cycle.php http://www.layyous.com/Videoclips/menstr ual%20cycle.htmhttp://www.layyous.com/Videoclips/menstr ual%20cycle.htm http://www.youtube.com/watch?v=pQ4QO Qdnifkhttp://www.youtube.com/watch?v=pQ4QO Qdnifk