menstrual cycle

• Hormones


  Chemicals released by glands into the bloodstream that trigger effects in specific target organs
• Endocrine system


  • The system that involves the release of hormones into the bloodstream
• Secondary sexual characteristics


  Physical features that develop during puberty and distinguish the two sexes, e.g. facial hair in men
• Testosterone


  Hormone produced by the testes that stimulates the production of sperm
• Estrogen


  Hormone produced by the ovaries that causes eggs to mature
• Ovulation


  The release of a mature egg from the ovary
• Menstrual cycle


  The cyclical changes in the uterus lining and the release of an egg every 28 days
• Menstrual cycle


  1. Uterus lining becomes thick and spongy

  2. Egg released from ovary

  3. Egg travels to uterus

  4. If egg not fertilized, egg and uterus lining are released as a period
• Key hormones in the menstrual cycle

  • Follicle Stimulating Hormone (FSH)
  • Luteinizing Hormone (LH)
  • Estrogen
  • Progesterone
• Follicle Stimulating Hormone (FSH)


  Causes an egg to mature in the ovary
• Luteinizing Hormone (LH)


  Causes the mature egg to be released (ovulation)
• Estrogen


  Maintains the uterus lining in case the egg is fertilized
• Progesterone


  Maintains the uterus lining in case the egg is fertilized, and stops the pituitary gland from releasing more FSH and LH
• Menstrual cycle hormonal changes

  1. FSH released by pituitary gland

  2. FSH causes egg to mature and ovaries to produce estrogen

  3. Estrogen inhibits further FSH release

  4. LH released by pituitary gland

  5. LH triggers ovulation

  6. Ovary produces progesterone after ovulation

  7. Progesterone maintains uterus lining

  8. If no fertilization, progesterone levels fall and uterus lining is shed (period)
• Higher tier students may be asked to interpret graphs of hormone levels during the menstrual cycle