The Menstrual Cycle

Question 1

What is the Follicular Phase of the menstrual cycle?

Answer 1

• FSH is secreted and stimulates the growth of ovarian follicles.
• The dominant follicle produces oestrogen, which inhibits FSH secretion (-ve feedback), to prevent other follicles from maturing.
• Oestrogen acts on the uterus to stimulate the thickening of the endometrial layer.

Question 2

What happens during Ovulation (~day 14)?

Answer 2

• Oestrogen stimulates the anterior pituitary to secrete hormones (+ve feedback).
• +ve feedback results in a large surge of LH and a lesser surge of FSH.
• LH causes the dominant follicle to rupture and release an egg.

Question 3

What happens during the Luteal Phase?

Answer 3

• The ruptured follicle develops into a slowly degenerating corpus luteum.
• The corpus luteum secretes high levels of progesterone.
• Oestrogen and progesterone thicken endometrium, and inhibit FSH and LH secretion to prevent follicle development.

Question 4

What happens during Menstruation, if fertilisation occurs?

Answer 4

• The developing embryo will implant in the endometrium and release hormones to sustain the corpus luteum.

Question 5

What happens during Menstruation, if fertilisation does NOT occur?

Answer 5

• Corpus luteum eventually degenerates, so oestrogen and progesterone levels drop.
• The endometrium can no longer be maintained, and is sloughed away as menstrual blood (period).
• The cycle can now be repeated again.