Menstrual Cycle

• Menstrual cycle


  Series of changes that occur in sexually mature, nonpregnant females and that culminate in menses
• Menses


  Period of mild hemorrhage, during which part of the endometrium is sloughed and expelled from the uterus
• Menstrual cycle is about 28 days long, but can be as short as 18 days or as long as 40 days
• Menorrhagia


  Prolonged or heavy menstrual bleeding that occurs in regular interval
• Metrorrhagia


  Irregular intervals of menstrual bleeding
• Menometrorrhagia


  Abnormally heavy, prolonged, and irregular menstrual bleeding
• Menstrual cycle


  1. Menses

  2. Proliferative phase

  3. Secretory phase

  4. Ovulatory phase
• Day 1 of menstrual cycle

  First day of menses
• Menses


  • Characterized by sloughing off of the endometrial lining
  • Typically lasts 4 to 5 days
  • Accompanied by strong uterine contractions called the menstrual cramps
• Progesterone level declines


  Sloughing off of the endometrial lining
• Menstrual cramps


  Result of forceful myometrial contractions that occur before and during menstruation
• Prostaglandins


  Excessive secretion of prostaglandins can result in menstrual cramps
• NSAIDs


  Drugs that inhibit the synthesis of prostaglandins, commonly used for menstrual cramps
• Proliferative phase


  • Proliferation of the endometrium
  • Secondary follicles start secreting estrogen
  • Estrogen stimulates epithelial cells to divide rapidly
  • Causes thickening of the endometrium and spiral glands form
• Spiral glands


  Uterine glands that synthesize substances essential for the survival and development of the embryo
• Positive feedback loop in proliferative phase

  1. Increasing estrogen stimulates GnRH secretion from hypothalamus

  2. GnRH stimulates pituitary to release LH and FSH

  3. FSH stimulates follicles to produce more estrogen
• Ovulation


  Occurs in response to the large increases in LH levels, usually on day 14 of menstrual cycle
• Ovulatory phase


  1. Large increase in LH levels causes development of corpus luteum

  2. Corpus luteum secretes progesterone and small amount of estrogen

  3. Progesterone acts on uterus, causing endometrial cells to become larger

  4. Negative feedback loop inhibits release of GnRH, LH and FSH after ovulation
• Secretory phase


  • Secretion of small amount of fluid by the cells in the endometrium
  • Endometrial lining reaches greatest degree of development
  • Prepared to receive blastocyst for implantation if fertilization occurs
• Declining progesterone level


  Causes endometrium to slough away and begin next menses
• Fertilization occurs in the Fallopian/Uterine Tube, and Implantation occurs within the uterus
• Menopause


  Cessation of menstrual cycles, occurs when a woman is 40 to 50 years old
• Climacteric


  Period from onset of irregular cycles to their complete cessation
• Primary amenorrhea


  Pituitary gland does not function properly, woman does not begin to menstruate at puberty
• Secondary amenorrhea


  Woman has had normal menstrual cycles and later stops menstruating
• Common reasons for secondary amenorrhea

  • Anorexia
  • Physical stress
  • Pituitary tumor
  • Polycystic ovarian syndrome