Menstrual Cycle Worksheet – Honors
1. What event is used to mark the start of the menstrual cycle? The start of menstruation
2. Which hormones are released from the pituitary gland at the beginning of the cycle? FSH and LH
3. On what organ does FSH act? A follicle in one of the ovaries
4. Name 2 changes that occur in the ovaries as a result of rising FSH levels.
 An egg in the follicle begins to mature.
 The follicle produces estrogen.
5. What does estrogen do to the lining of the uterus? It causes the lining to thicken
6. What signal in the blood reduces the production of FSH by the pituitary and limits the production of LH?
Increasing, but still relatively low amounts of estrogen
7. What signal later causes a rapid rise in the levels of FSH and LH?
High levels of estrogen
8. When does ovulation usually occur? 14 days before the start of the next cycle (around day 14 for a typical
28 day cycle)
9. What triggers ovulation? A rapid rise in LH
10. After ovulation what happens to the ruptured follicle? It is converted to a corpus luteum.
11. What causes this change? LH
12. What hormones are secreted by the corpus luteum? estrogen and progesterone
13. What does the hormone progesterone do to the lining of the uterus? It stimulates tissue growth and
increases blood supply.
14. What happens to the corpus luteum if the egg is not fertilized? It breaks down after 14 days.
15. What triggers the start of menstruation if the egg is not fertilized? When the corpus luteum breaks down,
levels of estrogen and progesterone fall. The lower levels of these hormones trigger menstruation.
16. When in the cycle would progesterone levels be highest? after ovulation (in the luteal phase)
17. What happens to the corpus luteum if the egg has been fertilized? HCG from the zygote signals the corpus
luteum to continue functioning. It will last for about the first 3 months of pregnancy. After that the placenta
will continue to produce estrogen and progesterone.
18. What would you predict about the level of progesterone in a pregnant woman? It would be high.
19. Why is this cycle an important adaptation for reproductions in humans? This communication between the
pituitary, the ovaries, and the uterus helps to synchronize the release of the egg with the optimum
preparation of the uterus. Hormones in the cycle ensure that the egg is only released when the uterus is in
the final stages of preparation. This way, if the egg is fertilized, the uterus will be at its thickest when the
embryo arrives.