The menstrual cycle

LH

What causes a ruptured follicle to be converted to a corpus lutem

It causes the lining to thicken

What does estrogen do to the lining of the uterus?

It stimulates tissue growth and increase blood supply.

What does the hormone progesterone do to the lining of the uterus?

The start of menstruation

What event is used to mark the start of the menstrual cycle

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?

It breaks down after 14 days

What happens to the corpus luteum if the egg is not fertilized?

Estrogen and progesterone

What hormones are secreted by the corpus luteum?

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?

A rapid rise in LH

What triggers ovulation?

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?

14 days before the start of the next cycle (around day 14 for a typical 28 day cycle)

When does ovulation usually occur?

After ovulation (in the luteal phase)

When in the cycle would progesterone levels be highest?

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?

FSH and LH

2. Which hormones are released from the pituitary gland at the beginning of the cycle?

It is converted to a corpus luteum

After ovulation what happens to the ruptured follicle?

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.

A follicle in one of the ovaries

On what organ does FSH act?

What would you predict about the level of progesterone in a pregnant women?

It would be high.