Female Reproductive System Function

Introduction

• Female reproductive system is more complex than the male.
• Oogenesis: process by which gametes (eggs) are made, referred to as oocytes or ova.
• Female gamete production begins before birth, pauses until puberty, resumes, and ceases at menopause.

Development of Oocytes

• Females are born with primary oocytes, arrested in meiosis I.
• Primary oocytes are surrounded by follicle cells, forming primordial ovarian follicles.
• Atresia: natural degeneration of many potential gametes.
• At puberty, hormonal signals reactivate oocyte development.

Ovarian and Uterine Cycles

• Two cycles work symbiotically: Ovarian Cycle and Uterine Cycle.
• Ovarian Cycle: Involves maturation and release of oocyte (ovulation).
• Uterine Cycle: Prepares uterus for potential fertilization and implantation.

Ovarian Cycle Phases

1. Follicular Phase (~first 2 weeks):

   • Follicle development and oocyte maturation.
   • Primary ovarian follicles develop into secondary and then tertiary ovarian follicles (Graafian or mature follicle).
   • Zona pellucida and antrum form during this phase.
   • Thecal cells secrete androgens converted to estrogen by follicular cells.

2. Ovulation:

   • Triggered by a surge in luteinizing hormone from the pituitary gland.
   • Primary oocyte completes meiosis I, forms secondary oocyte and a polar body.
   • Secondary oocyte begins meiosis II but is arrested unless fertilization occurs.
   • Secondary oocyte is released from the ovary.
   • Uterine tubes guide the oocyte into the uterine tube, aided by fimbriae and cilia.

3. Luteal Phase (~second 2 weeks):

   • Post-ovulation, forming the Corpus luteum from the follicle.
   • Corpus luteum secretes progesterone, crucial for uterine preparation.
   • If no fertilization, the corpus luteum degenerates into the Corpus albicans.

Summary

• Ovarian cycle is approximately 28 days, with variations among individuals.
• Involves complex interactions between hormones and anatomical changes.
• Important roles of estrogen and progesterone in different phases.
• Reproductive cycle restarts if no fertilization occurs.