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The menstrual cycle
Terms in this set (19)
The start of menstruation
What event is used to mark the start of the menstrual cycle
FSH and LH
2. Which hormones are released from the pituitary gland at the beginning of the cycle?
A follicle in one of the ovaries
On what organ does FSH act?
An egg in the follicle begins to mature.
The follicle produces estrogen.
Name 2 changes that occur in the ovaries as a result of rising FSH levels.
It causes the lining to thicken
What does estrogen do to the lining of the uterus?
Increasing, but still relatively low amounts of estrogen
What signal in the blood reduces the production of FSH by the pituitary and limits the production of LH?
High levels of estrogen
What signal later causes a rapid rise in the levels of FSH and LH?
14 days before the start of the next cycle (around day 14 for a typical 28 day cycle)
When does ovulation usually occur?
A rapid rise in LH
What triggers ovulation?
It is converted to a corpus luteum
After ovulation what happens to the ruptured follicle?
What causes a ruptured follicle to be converted to a corpus lutem
Estrogen and progesterone
What hormones are secreted by the corpus luteum?
It stimulates tissue growth and increase blood supply.
What does the hormone progesterone do to the lining of the uterus?
It breaks down after 14 days
What happens to the corpus luteum 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.
What triggers the start of menstruation if the egg is not fertilized?
After ovulation (in the luteal phase)
When in the cycle would progesterone levels be highest?
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.
What happens to the corpus luteum if the egg has been fertilized?
What would you predict about the level of progesterone in a pregnant women?
It would be high.
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.
Why is the cycle an important adaptation for reproductions in humans?
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