menstrual cycle

• Menstrual cycle events

  Day 1 - Day 28: Ovulation, Hormone release, Pituitary gland, Ovary, Uterus, Follicle stimulating hormone, Luteinising hormone, Oestrogen, Progesterone
• Ovaries


  • Produce female gametes (eggs) and hormones oestrogen and progesterone
• Cervix

  • A ring of muscle at the opening of the uterus
• FSH

  Follicle Stimulating Hormone: Made in the pituitary gland, causes eggs to mature, stimulates ovary to produce oestrogen
• Oviduct


  • Carries eggs (ova) to the uterus, lined with ciliated epithelial cells
• Vagina


  • Receives the penis during sexual intercourse
• LH

  Luteinising Hormone: Released around day 14, causes egg release from the ovary
• The menstrual cycle is a series of related events that happen in the pituitary gland, ovaries, and uterus. It prepares the body for pregnancy and takes, on average, 28 days
• Menstrual cycle details

  The cycle begins with shedding of the old egg and lining, new egg maturing in the ovary, FSH release, production of oestrogen, thickening of uterine lining, LH release, ovulation, egg reaching the uterus, thickening of the womb lining for embryo protection and food, potential fertilization leading to cycle continuation or shedding of the egg
• Uterus


  • Has a thick lining (endometrium) for implantation of a fertilised egg
• Ovulation in a Human

  1. Girls are born with thousands of partly developed egg cells in each ovary

  2. At the start of each cycle an egg cell develops into a follicle by building layers of follicle cells around it

  3. After 2 weeks the mature follicle bursts releasing the egg (ovulation) into the oviduct
• LH

  Luteinising hormone, released around day 14, causes the egg to be released from the ovary
• Oestrogen

  Produced in the ovaries, causes the lining of the uterus to get thicker, contained in the contraceptive pill
• FSH and Oestrogen are the two hormones used in the contraceptive pill because they cause the release of eggs and help prevent pregnancy
• Key for hormones in the contraceptive pill

  • F - FSH
  • O - Oestrogen
  • L - Luteinising Hormone
  • P - Progesterone
• FSH

  Follicle Stimulating Hormone, made in the pituitary gland in the brain, causes eggs to mature, stimulates the ovary to produce oestrogen
• FSH


  Stimulates production of follicles
• If fertilisation does not occur

  Egg dies and the uterus lining breaks down and is lost during menstruation
• The menstrual cycle is controlled by a number of hormones produced by glands in the reproductively mature female
• Formation of corpus luteum

  Follicle cells remaining on the ovary surface and forming the corpus luteum which maintains the lining of the uterus during pregnancy
• Mature follicle bursting and releasing the egg

  Ovulation into the oviduct
• If fertilisation occurs

  Egg cell divides by mitosis to form a ball of cells and implants in the thickened uterine lining
• Stages in the menstrual cycle – hormones

  1. Pituitary gland secretes FSH which stimulates a follicle to develop

  2. FSH also stimulates the developing follicle to secrete oestrogen which causes the uterine lining to repair and thicken and inhibits production of FSH

  3. Oestrogen levels peak and cause the pituitary gland to release LH resulting in ovulation

  4. Corpus luteum secretes progesterone which maintains the uterine lining and inhibits LH secretion
• Hormones involved in the female menstrual cycle

  • FSH
  • Oestrogen
  • LH
  • Progesterone
• LH


  Results in ovulation
• Testes produce male gametes (sperm) and the hormone (testosterone)
• Scrotum hangs outside of the body to keep testes cool for optimum sperm production
• Progesterone


  Maintains the uterine lining, inhibits LH secretion
• Summary of hormone interactions

  • FSH
  • Oestrogen
  • LH
  • Progesterone
• Development of an egg cell into a follicle

  Building layers of follicle cells around the egg cell
• Oestrogen


  Causes the uterine lining to repair and thicken, inhibits production of FSH