Menstrual cycle

• Puberty - period in which adolescents start to develop secondary sexual characteristics. Triggered by testosterone and oestrogen.
• Menstrual cycle;

  STAGE 1 : 'menstruation' ,breakdown of uterus lining, bleeding, (0 - 4 days)

  STAGE 2 : uterus lining starts to build up, prepares for fertilised egg (4 - 14 days)

  STAGE 3 : 'ovulation' , egg is released (14 day)

  STAGE 4 : maintaining the lining of uterus (15 - 28 days)
• Oestrogen - form the ovaries, stimulates lining of uterus to grow, high in stage 2.
• Progesterone - from the empty egg follicle, maintains the lining of the uterus, high in stage 4.
• Luteinising hormone (LH) - from pituitary gland, stimulates the release of the egg, high in stage 3.
• Follicle-stimulating hormone (FSH) - from pituitary gland, stimulates one of the eggs to mature, high in stage 3.
• How hormones interact together during the menstrual cycle:

  • FSH stimulates ovaries to produce oestrogen
  • As oestrogen levels rise, it will inhibit the FSH
  • Also as oestrogen levels are high, they will stimulate the release of LH
  • Progestrogen inhibits both LH and FSH