Menstruation Cycle

• How long does the average menstrual cycle last?

  28 days, the first day of menstruation is regarded as day one of the cycle
• What does the pituitary gland secrete?

  FSH and LH
• What does FSH in females do?

  Stimulates development of a follicle and the production of oestrogen by the follicle
• What does oestrogen stimulate?

  The proliferation of the endometrium preparing it for implantation
• What else does oestrogen affect?


  The consistency of the cervical mucus, making it more easily penetrated by sperm
• What happens when oestrogen levels peak?

  Peak levels of oestrogen stimulate a surge in the secretion of LH; this surge in LH triggers ovulation
• What do high levels of oestrogen do?


  Inhibit FSH production, which prevents further follicles from developing; this is negative feedback
• What happens to the follicle after ovulation/in the luteal phase?

  The follicle develops into a corpus luteum, this secretes progesterone
• What does progesterone do?

  Stimulates the thickening of the endometrium preparing it for implantation if fertilisation occurs
• What does progesterone inhibit?

  FSH and LH production
• What does the lack of LH (inhibited by progesterone) cause?

  Corpus luteum degeneration; this leads to a decrease in progesterone levels, which triggers menstruation
• What happens if fertilisation occurs?

  The corpus luteum does not degenerate, and progesterone levels remain high
• Would a pregnant woman have high or low progesterone levels?

  High, because her corpus luteum did not degenerate, and continued to secrete progesterone
• How does oestrogen cause ovulation?

  Oestrogen stimulates the secretion of LH, and this surge in LH triggers ovulation