Review of Guyton and Hall's Medical Physiology - Chapter 82: Female Physiology

Introduction

• Focus on female physiology, particularly the reproductive function.
• Two stages of reproductive function:
  • Preparation for conception and pregnancy.
  • Period of pregnancy.
• Chapter covers the first stage, highlighting the formation and development of eggs.

Egg Development

• Females provide the egg (oocyte) while males provide sperm.
• Embryonic Development:
  • Oocyte differentiates into an ovum.
  • Undergoes mitotic replication and first stage of meiosis within first five months of fetal development.
  • All eggs (primordial ova) formed in embryonic stage.
  • Eggs surrounded by ovarian stroma forming granulosa cells.

Puberty and Egg Maturation

• 1-2 million primary oocytes at birth, diminishes to 300,000 by puberty.
• Meiotic Division:
  • Two cells per egg: larger ovum and polar body (disintegrates).
  • Monthly release of one ovum post-puberty.

Hormonal Regulation

• Three Hierarchies:
  • Hypothalamus: Releases GnRH (gonadotropin-releasing hormone).
  • Pituitary Gland: Releases FSH (follicle-stimulating hormone) and LH (luteinizing hormone).
  • Ovaries: Produce estrogen and progesterone.
• Menstrual Cycle:
  • Approximately 28-day cycle.
  • Ovulation regulated by LH spike.

FSH and LH Functions

• FSH: Stimulates follicle development.
• LH: Causes ovulation and conversion of granulosa cells to progesterone-secreting cells.
• Estrogen: Positive feedback mechanism, increasing sensitivity to FSH and LH.

Follicle Development and Ovulation

• Competing follicles with one reaching maturity.
• LH Surge:
  • Occurs two days before ovulation.
  • Converts follicle to corpus luteum (progesterone secretion).
  • Ovulation involves enzymatic dissolution and follicle wall thinning.

Hormonal Feedback Loops

• Estrogen: Negative feedback initially, then a positive feedback leading to LH spike.
• Progesterone: Inhibits LH and FSH, maintaining corpus luteum.
• Cycle Continuation: Corpus luteum fades, allowing FSH and LH rise.

Menstrual Cycle Phases

• Proliferative Phase: Under estrogen, promoting endometrial growth.
• Secretory Phase: Post-ovulation with progesterone and estrogen thickening the endometrium.
• Menstrual Phase: Shedding of endometrial lining.

Estrogen and Progesterone Effects

• Estrogen:
  • Promotes sexual organ growth, inhibits osteoclastic activity, increases metabolism.
  • Effect on bone growth and deposition of fat, smooth skin texture.
• Progesterone:
  • Increases functional components of sexual organs, supports uterine lining maturation.

Menopause and Hormonal Changes

• Menopause: Cessation of cycle due to depleted follicles.
• Symptoms: Hot flashes, irritability, decreased bone strength.
• Estrogen Therapy: Can affect cardiovascular disease risk if started early.

Female Sexual Response and Fertility

• Sexual Stimulation: High estrogen levels during ovulation increase sexual responsiveness.
• Fertility Timing: Intercourse timing critical for fertilization, with sperm viability up to 5 days.

Contraception Methods

• Rhythm Method: Based on timing ovulation, less reliable.
• Hormonal Contraceptives: Inhibit ovulation by steady hormonal levels.

Infertility Causes

• Most Common: Lack of ovulation due to hormone issues.
• Endometriosis: Abnormal growth of endometrial tissue causing fertility issues.

Conclusion

• Summary of chapter, understanding female physiology and hormonal interplay critical for medical understanding.