The 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. pubic hair in men
• Testosterone


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


  Hormone produced by the ovaries
• Ovulation


  The release of an egg from the ovary every 28 days
• Menstrual cycle


  The 28-day cycle involving the release of an egg and the preparation of the uterus lining
• 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 produced by the ovary 


  Maintains the uterus lining
• Progesterone


  Maintains the uterus lining and prevents further egg maturation and release
• Menstrual cycle


  1. FSH released by pituitary gland

  2. FSH causes egg maturation and estrogen production in ovary

  3. Estrogen inhibits further FSH release

  4. LH released by pituitary gland

  5. LH triggers ovulation

  6. Ovary releases progesterone

  7. Progesterone maintains uterus lining

  8. If no fertilization, progesterone levels fall, uterus lining shed (period)