Biology 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
• Reproductive hormones


  Hormones that cause secondary sexual characteristics to develop during puberty
• Testosterone


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


  • Hormone produced by the ovaries that causes eggs to mature
• Menstrual cycle


  1. Egg released every 28 days

  2. Uterus lining becomes thick and spongy

  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, stops further eggs from maturing/being released
• Menstrual cycle hormonal interactions

  1. FSH released by pituitary gland

  2. FSH causes egg maturation and estrogen production in ovaries

  3. Estrogen inhibits further FSH release

  4. LH released by pituitary gland

  5. LH triggers ovulation

  6. After ovulation, ovary releases progesterone

  7. Progesterone maintains uterus lining, stops further eggs maturing/releasing

  8. If no fertilization, progesterone levels fall, uterus lining and egg shed (period)
• Graphs of hormone levels during the menstrual cycle could be asked about in exams