The mammalian oestrous cycle is controlled by FSH, LH, progesterone and oestrogen. The secretion of FSH, LH, progesterone and oestrogen is controlled by interacting negative and positive feedback loops. Candidates should be able to interpret graphs showing the blood concentrations of FSH, LH, progesterone and oestrogen during a given oestrous cycle. Changes in the ovary and uterus lining are not required.

A follicle is an egg, cells that create oestrogen and fluid.

On day 1 you get your period (for 5 days). FSH is maturing a follicle.

The follicle is producing low levels of oestrogen which develop the womb lining and keep FSH and LH production down.

As the follicle develops, it begins to produce more oestrogen. When oestrogen production reaches threshold it increases the production of FSH and LH.

The peak in LH causes the follicle to rupture, releasing the egg (ovulation) (day 14). The egg travels towards the uterus.

The follicle becomes a corpus luteum, which secretes progesterone and oestrogen.

Progesterone maintains the womb lining. It also inhibits LH and FSH (preventing another egg from being released). (This is in preparation for fertilisation, but if that doesn't happen then:)

After a few days the corpus luteum withers and stops producing progesterone so the womb lining breaks down (this causes the period days 1-5).