1. Menstrual Cycle

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

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 Ovulation Luteal Phase Menstruation
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. The Menstrual Cycle Ovulation
The menstrual cycle is divided into four phases. Notice the changes in hormone levels in the blood, the development of the follicle, and the changes in the uterine lining during the menstrual cycle.
Copyright Pearson Prentice Hall 9

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 Ovulation Luteal 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
Control by hypothalamus
Inhibited by combination of
estrogen and progesterone
Hypothalamus
Stimulated by high levels
of estrogen
GnRH
Anterior pituitary
Inhibited by low levels of
estrogen
FSH LH
Pituitary gonadotropins
in blood LH
FSH
FSH and LH stimulate
follicle to grow
LH surge triggers
ovulation
Ovarian cycle
Corpus
luteum
Degenerating
corpus luteum
Growing follicle
Mature
follicle
Follicular phase
Ovulation
Luteal phase
Estrogen secreted
by growing follicle in
increasing amounts
Progesterone and
estrogen secreted
by corpus luteum
Ovarian hormones
in blood
Peak causes
LH surge
This figure shows how c. the ovarian cycle and E. the uterine(menstrual cycle) are regulated by changing hormone levels in the blood depicted in parts a. b. and d. The time scale at the bottom of the figure applies to parts b-e.
Estrogen
Progesterone
Estrogen level
very low
Progesterone and estro-
gen promote thickening
of endometrium
Uterine (menstrual) cycle
Endometrium
Menstrual flow phase
Proliferative phase
Secretory phase
Days 5 10 14 15 20 25 28

14. Websites for Menstruation