menstural 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 that causes eggs to mature
• Ovulation


  The release of a mature 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
• Menstrual cycle


  1. Egg matures in ovary

  2. Egg is released (ovulation)

  3. Egg travels to uterus

  4. If egg is fertilized, it implants in uterus wall

  5. If egg is not fertilized, it and uterus lining are shed (period)
• 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
• FSH is released


  Causes an egg to mature in the ovary, triggers the ovaries to produce estrogen
• Estrogen levels increase


  Stops the pituitary gland from releasing more FSH
• LH is released


  Triggers ovulation, the release of the mature egg
• After ovulation


  The ovary produces progesterone
• Progesterone levels


  Prevent the pituitary gland from releasing more FSH and LH, keep the uterus lining thick
• If the egg is not fertilized

  Progesterone levels fall, the uterus lining and egg are shed (period)
• Graphs of hormone levels during the menstrual cycle could be asked about in exams