L4.3.1: Menstrual Cycle

• Menstrual Cycle

  ● Rhythmical series of physiological changes that occur in fertile women when beginning puberty.

  ○ Menarche

  ● Under the control of the endocrine system.

  ○ Targets the sex organ (gonads) for producing its sex hormones.

  ● Necessary for reproduction.
• Menstrual Cycle

  ● Average length: 28 days

  ○ Typically varies, with shorter (25 days) and longer (35 days) cycles.

  ● Consists of:

  ○ Ovarian Cycle

  ○ Uterine Cycle

  ● General Fertility Years: 39 years
• Menarche

  ● Onset

  ● A woman’s first menstruation.

  ● Typically occurs around age 12.

  ● Occurrence depends on overall health and diet.

  ● Sometimes manifested with the mother’s first menstruation.
• Menopause

  ● Cessation

  ● End of woman’s reproductive phase.

  ● Occurs between ages 45 and 55.

  ● Age of menopause is largely the result of genetics.

  ● Formula for the Age of Menopause

  ○ age of menarche + 39 years
• Levels of Menstrual Cycle

  • Neuroendocrine Level
  • Ovaries (Ovarian)
  • Uterus (Uterine)
• FSH

  ● Follicular Growth

  ● Estrogen Secretion

  ● Site: Anterior Pituitary
• ESTROGEN

  ● Development of Endometrium

  ● LH Suppression (FollicularP)

  ● Inhibits LH and FSH (LutealP)

  ● Site: Ovaries
• LH

  ● Its surge causes ovulation

  ● Development of Corpus Luteum

  ● Progesterone Secretion

  ● Site: Anterior Pituitary
• PROGESTERONE

  ● Thickening of Endometrium

  ● Inhibits LH and FSH (LutealP)

  ● Site: Ovaries
• GnRH

  ● Signals the pituitary gland to release the gonadotropin hormones: LH and FSH

  ● Site: Hypothalamus