Physiology of the Female Reproductive System

Overview

• More complex than the male system.
• Main Topics Covered:
  • Oogenesis (production of female gametes).
  • Ovarian and Uterine Cycles.
  • Fertilization and Implantation.
  • Hormonal changes during pregnancy.

Oogenesis

• Definition: Formation of female gametes (oocytes).
• Begins in females before birth during embryonic development.
• Process:
  • Germ cells migrate to ovaries, differentiate into oogonia (46 chromosomes).
  • Oogonia divide, many degenerate before birth.
  • Remaining develop into primary oocytes.
  • Primary oocytes enter meiosis, arrested until puberty, forming primordial follicles.
• Numbers:
  • At birth: ~200,000 oocytes per ovary.
  • At puberty: ~40,000 remain; ~400 mature during reproductive lifetime.
• Development:
  • Influenced by gonadotropins (FSH and LH).
  • Primordial follicles develop into primary and then secondary follicles.
  • Secondary follicle becomes mature follicle, ovulates.
  • Meiosis resumes if fertilization occurs.

Female Reproductive Cycles

Ovarian Cycle

• Phases:
  • Follicular Phase (Day 1-14):
    • FSH stimulates follicle growth.
    • Estrogen secretion prepares uterus.
  • Ovulation (Day 14):
    • Triggered by LH surge.
    • Mature follicle ruptures, releases secondary oocyte.
  • Luteal Phase (Day 14-28):
    • Corpus luteum forms, secretes hormones (progesterone, estrogen).
    • Prepares endometrium for potential implantation.

Uterine Cycle (Menstrual Cycle)

• Phases:
  • Menstrual Phase (Day 1-5):
    • Shedding of stratum functionalis due to declining hormone levels.
  • Proliferative Phase (Day 5-14):
    • Estrogen rebuilds endometrium.
  • Secretory Phase (Day 14-28):
    • Progesterone increases endometrial thickness.
    • Prepares for implantation.

Fertilization and Implantation

• Fertilization:
  • Occurs in the uterine tube.
  • Sperm must undergo capacitation.
  • Sperm penetrates corona radiata and zona pellucida.
  • Acrosomal reaction allows sperm to reach oocyte membrane.
  • Prevention of polyspermy via fast and slow block mechanisms.
• Implantation:
  • Zygote travels, implants in uterine wall.
  • Occurs about 6 days post-fertilization.

Hormonal Changes during Pregnancy

• Early Pregnancy:
  • Corpus luteum secretes hormones to maintain uterus lining.
  • HCG from embryo maintains corpus luteum function.
• Later Pregnancy:
  • Placenta takes over hormone production.
  • Estrogen and progesterone from placenta maintain pregnancy.
  • Relaxin increases pelvic flexibility and aids in delivery.

Anatomical and Physiological Changes in Pregnancy

• Anatomical Changes:
  • Uterus expands into abdominal cavity.
  • Displacement of organs, diaphragm elevation.
• Physiological Changes:
  • Weight gain, increased cardiac output.
  • Changes in urinary, gastrointestinal, respiratory, and skin systems.

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These notes summarize the key points from the lecture on the female reproductive system, providing a comprehensive overview of the processes involved in oogenesis, the reproductive cycles, fertilization, and the physiological changes during pregnancy.