2 LESSON_Q3

• Menstrual cycle

  • It is the series of natural changes that occurs in the uterus and in the ovary
  • It is regulated by different female reproductive hormones
  • It takes around 28 days in humans
• Phases of the ovarian cycle

  • Follicular phase (days 1-13)
  • Ovulation phase (day 14)
  • Luteal phase (days 15-28)
• Phases of the uterine cycle

  • Menstruation phase
  • Proliferative phase
  • Secretory phase
• Menstrual cycle regulation


  1. GnRH is released by the hypothalamus

  2. GnRH triggers the anterior pituitary lobe to secrete FSH and LH

  3. FSH and LH stimulate follicle growth in the ovary

  4. Follicles start to make estrogen

  5. Around day 12, estrogen levels rise steeply

  6. Rising estrogen stimulates an LH surge

  7. LH surge triggers ovulation

  8. Follicles left in the ovary form the corpus luteum, which secretes progesterone and estrogen

  9. Rising progesterone and estrogen levels stimulate thickening of the endometrium

  10. If pregnancy occurs, the corpus luteum continues to secrete progesterone and estrogen to maintain the endometrium; otherwise it disintegrates and hormone levels drop, resulting in the loss of the endometrial tissue as menstrual flow
• The menstrual cycle continues for about 450 cycles, then women enter menopause, which marks the end of the menstrual cycle
• Menopause typically occurs in females around 40-50 years of age
• Symptoms of menopause


  • Irregular periods
  • Vaginal dryness
  • Sleep problems
  • Hot flashes
  • Mood swings
  • Weight gain
  • Dry skin
  • Thinning hair
  • Night sweating
  • Decreasing breast fullness
• The pituitary gland controls and starts the menstrual cycle
• The pituitary gland releases hormones that cause the egg in the ovary to mature
• The luteinizing hormone (LH) triggers ovulation
• Corpus luteum


  Gland that secretes progesterone and estrogen
• Menstrual cycle


  1. Rising progesterone and estrogen levels stimulate thickening of the endometrium

  2. If pregnancy occurs, corpus luteum continues to secrete progesterone and estrogen to maintain the endometrium

  3. If no pregnancy, corpus luteum disintegrates and hormone levels drop, resulting in loss of endometrial tissue as menstrual flow

  4. Cycle continues for about 450 cycles, then menopause occurs
• Menopause


  • Marks the end of the menstrual cycle
  • Occurs in females around 40-50 years of age
  • May include irregular periods, vaginal dryness, sleep problems, hot flashes, mood swings, weight gain, dry skin, thinning hair, night sweating, decreasing breast fullness
• Menstrual cycle


  1. Pituitary gland controls and starts the cycle

  2. Pituitary gland releases hormones that cause egg in ovary to mature

  3. Luteinizing hormone (LH) initiates follicle maturation, converts ruptured follicles into corpus luteum, causes progesterone secretion

  4. Follicle stimulating hormone (FSH) assists in follicle maturation, causes estrogen secretion from follicles

  5. Ovary releases estrogen, causing uterine lining to thicken

  6. Ovary releases egg on day 14

  7. Egg moves through oviduct and enters uterus

  8. Uterine lining continues to thicken

  9. Unfertilized egg is not attached to uterus, uterine lining is shed as menstruation

  10. Cycle starts again after menstruation
• Menstrual cramps


  • Result of strong contractions of uterine wall before and during menstruation
  • Caused by excessive secretion of prostaglandins
• Nervous system and endocrine system


  Work together to maintain homeostasis
• Homeostasis


  • State reached when each part of the body functions in equilibrium with other parts
  • Attained through regulation of bodily functions by endocrine and nervous systems
  • Maintained using feedback mechanisms
• Variables maintained for homeostasis

  • Body temperature
  • Amount of water in the body
  • Amount of metabolic wastes in the cell
  • Blood calcium level
  • Hormones in the blood