menstrual cycle

• how often does the menstrual cycle occur?

  28 days
• what is menstruation?

  menstruation is the breakdown of the uterus lining (starts on day1-day5)
• what is ovulation?


  release of an egg from the ovary (day14)
• what is fertilisation?


  when an egg and sperm cell fuse to form a zygote
• when is fertilisation most likely to take place?

  day14-day16
• what happens in week 3 and 4?

  the uterus lining builds up
• low levels of progesterone allow FSH to be released
• high levels of oestrogen (day12/13) stimulate release of more LH
• increasing progesterone (after day 14) inhibits FSH and LH
• FSH stimulates growth and maturation of follicles at start of cycle
• LH surge trigger ovulation
• increase in oestrogen causes lining to thicken and grow
• surge of progesterone released by corpus lutes after ovulation
• progesterone maintains uterus lining and inhibits FSH and LH
• as progesterone and oestrogen levels fall, lining breaks down
• low progesterone allows FSH increase
• LH and FSH surge at day14 (ovulation)
• LH stimulates release of egg
• LH causes ovulation
• FSH causes follicle to mature
• Oestrogen causes an LH surge and inhibits FSH
• progesterone inhibits LH and FSH
• growing follicle secretes oestrogen
• if not fertilised, the corpus lutueum breaks down and progesterone levels fall