Reproductive system overview

Male Reproductive System - The Production Line

• Primary Function: Produce, maintain, and transport sperm & protective fluid (semen).
• Key Structures & Pathway:
  • Testis: Site of spermatogenesis (Seminiferous tubules) & testosterone production (Leydig cells).
  • Epididymis: Sperm maturation and storage.
  • Vas Deferens: Transports mature sperm.
  • Accessory Glands: Add seminal fluid.
    • Seminal Vesicles: Fructose (energy), prostaglandins.
    • Prostate Gland: Citrate, PSA.
    • Bulbourethral Glands: Pre-ejaculate (lubrication).

⭐ Exam Favorite: Seminal vesicles contribute ~70% of semen volume, providing fructose as the primary energy source for sperm motility.

📌 Mnemonic (Sperm Pathway): SEVEN UP - Seminiferous tubules, Epididymis, Vas deferens, Ejaculatory duct, Nothing, Urethra, Penis.

Female Reproductive System - The Ovarian Odyssey

• Ovary Anatomy: Cortex contains follicles; Medulla has blood vessels. Dual function: oogenesis & hormone production (estrogen, progesterone).
• Ovarian Cycle: A two-phase process driven by gonadotropins.
  • Follicular Phase (Days 1-14): FSH stimulates follicle growth, leading to ↑ estrogen.
  • Ovulation (Day 14): A surge in LH triggers the release of the oocyte.
  • Luteal Phase (Days 15-28): Corpus luteum forms, secreting progesterone.

⭐ High-Yield: The pre-ovulatory LH surge is the critical trigger for the primary oocyte (arrested in Prophase I) to complete Meiosis I, becoming a secondary oocyte (arrested in Metaphase II).

Gametogenesis - Crafting the Cells

• Gametogenesis: Production of gametes (sperm & ova) via meiosis, reducing chromosome number from diploid (2n) to haploid (n).

• Spermatogenesis:

  • Location: Seminiferous tubules.
  • Onset: Puberty; a continuous process.
  • Duration: ~74 days.
  • Result: 1 primary spermatocyte → 4 spermatozoa.

• Oogenesis:

  • Location: Ovaries.
  • Onset: In utero; a discontinuous process.
  • Result: 1 primary oocyte → 1 ovum + polar bodies.

⭐ Oocytes arrest in Prophase I from fetal life until puberty. After ovulation, the secondary oocyte arrests in Metaphase II until fertilization.

Hormonal Regulation - The Endocrine Orchestra

• HPG Axis: Pulsatile GnRH from the hypothalamus drives the pituitary to release LH & FSH, which target the gonads. Negative feedback regulates the system.

• Male Action:
  • LH → Leydig cells → Testosterone.
  • FSH → Sertoli cells → Spermatogenesis & Inhibin B.
  • 📌 LH stimulates Leydig; Sertoli Sustains Sperm.
• Female Action:
  • LH → Theca cells → Androgens.
  • FSH → Granulosa cells → Estradiol (via aromatase).

⭐ Failure of GnRH-producing neurons to migrate from the olfactory placode results in Kallmann syndrome (hypogonadotropic hypogonadism + anosmia).

High‑Yield Points - ⚡ Biggest Takeaways

• The left gonadal vein drains to the left renal vein; the right gonadal vein drains directly to the IVC.
• Testicular/ovarian lymph drains to paraaortic nodes; scrotal/vulvar lymph drains to superficial inguinal nodes.
• The suspensory ligament of the ovary contains the crucial ovarian artery and vein.
• Erection is parasympathetic (S2-S4); ejaculation is sympathetic (L1-L2).
• The round ligament of the uterus passes through the deep inguinal ring.
• The vas deferens joins the seminal vesicle duct, forming the ejaculatory duct within the prostate.