Reproductive System

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Male Anatomy - The Sperm Factory

Testis, epididymis, seminiferous tubule, spermatogenesis

  • Testes: Located in scrotum; primary functions are spermatogenesis (sperm production) and testosterone secretion.
    • Seminiferous Tubules: Site of spermatogenesis. Contain Sertoli cells (support, blood-testis barrier, inhibin, Androgen Binding Protein) & germ cells.
    • Leydig Cells (interstitial): Produce testosterone in response to LH.
    • Temperature: Maintained ~2-3°C below core body temperature, essential for sperm production.
  • Epididymis: Coiled tube for sperm maturation and storage.
  • Duct System: Vas deferens transports sperm; joins seminal vesicle duct to form ejaculatory duct, which empties into urethra.
  • Accessory Glands: Contribute seminal fluid.
    • Seminal Vesicles: ~60-70% of semen volume (fructose, prostaglandins).
    • Prostate Gland: ~20-30% (citrate, PSA).
    • Bulbourethral (Cowper's) Glands: Pre-ejaculate. 📌 Mnemonic (Sperm Pathway): SEVEN UP - Seminiferous tubules, Epididymis, Vas deferens, Ejaculatory duct, Nothing (placeholder), Urethra, Penis.

⭐ The Blood-Testis Barrier, formed by tight junctions between adjacent Sertoli cells, isolates developing gametes from the immune system, preventing an autoimmune response to sperm antigens which are recognized as foreign after puberty.

Female Anatomy - Ovary & Cycle Central

  • Ovary:
    • Cortex: Follicles (oogenesis).
    • Medulla: Vasculature, nerves.
    • Coverings: Germinal epithelium (simple cuboidal), Tunica albuginea.
  • Oogenesis: Oogonia → Primary oocyte (Prophase I arrest) → Secondary oocyte (Metaphase II arrest). Meiosis II completes post-fertilization.
  • Folliculogenesis: Primordial → Primary → Secondary (antral) → Graafian (mature) follicle.
    • Theca cells (LH-stimulated): Androgen production.
    • Granulosa cells (FSH-stimulated): Convert androgens to estrogen (aromatase).

      ⭐ LH surge precedes ovulation by 24-36 hours; actual ovulation occurs 10-12 hours after the LH peak.

Ovarian follicle development and corpus luteum formation

  • Menstrual Cycle (avg. 28 days):
    • Follicular (Proliferative) Phase (Day 1-14): FSH → follicle development → Estrogen (E₂)↑ → endometrial proliferation. Ends with LH surge.
    • Ovulation (~Day 14): LH surge → oocyte release.
    • Luteal (Secretory) Phase (Day 15-28): Corpus luteum forms → Progesterone (P₄)↑ (dominant), E₂↑ → secretory endometrium. If no fertilization, corpus luteum degenerates → P₄↓ & E₂↓ → menstruation.
    • 📌 Mnemonic for cycle phases: My Friend Often Laughs (Menstrual, Follicular, Ovulatory, Luteal).

Gametogenesis & Fertilization - Conception Essentials

  • Gametogenesis: Gamete formation.
    • Spermatogenesis: Seminiferous tubules; ~74 days. Spermatogonia → Spermatozoa.
    • Oogenesis: Ovary; starts prenatally. Primary oocyte (Prophase I arrest) → Secondary oocyte (Metaphase II arrest until fertilization).
  • Fertilization: Union of sperm & ovum; typically in ampulla.
    • Events: Capacitation → Acrosome reaction → Penetration (corona radiata, zona pellucida) → Fusion → Cortical reaction (prevents polyspermy) → Meiosis II completion → Zygote.
  • Implantation: Blastocyst into endometrium; ~6-12 days post-fertilization.
    • Gamete viability: Sperm 48-72 hrs; Oocyte 12-24 hrs.

Steps of human fertilization

⭐ Fertilization most commonly occurs in the ampullary region of the fallopian tube, the widest part.

  • Male Pathologies:
    • Testicular Torsion: Acute scrotal pain, absent cremasteric reflex. Bell-clapper deformity. ⚠️ Surgical emergency!
    • Varicocele: Dilated pampiniform plexus; "bag of worms". Often left-sided.
    • Benign Prostatic Hyperplasia (BPH): Common in elderly men; urinary obstruction.
    • Prostate Cancer: ↑ PSA; often adenocarcinoma in peripheral zone.
  • Female Pathologies:
    • PCOS: Anovulation, hyperandrogenism, polycystic ovaries. LH:FSH ratio > 2:1. Ultrasound: Normal vs Polycystic Ovary
    • Endometriosis: Ectopic endometrial tissue. Dysmenorrhea, infertility, "chocolate cysts".
    • Uterine Leiomyoma (Fibroids): Most common benign tumor in females.
    • Ectopic Pregnancy: Implantation outside uterine cavity. Ampulla is most common site.
  • Pelvic Inflammatory Disease (PID): Infection of upper genital tract. Can cause infertility, chronic pain.

    ⭐ Hydatidiform mole, a gestational trophoblastic disease, presents with markedly elevated hCG levels, "snowstorm appearance" on ultrasound, and grapelike vesicles.

High‑Yield Points - ⚡ Biggest Takeaways

  • Sertoli cells secrete Anti-Müllerian Hormone (AMH), inhibiting female internal genitalia development.
  • Leydig cells, stimulated by LH, produce testosterone responsible for male characteristics.
  • Prostatic utricle in males is a remnant of the paramesonephric (Müllerian) duct.
  • Gartner's duct in females is a remnant of the mesonephric (Wolffian) duct.
  • Oogenesis starts in utero; primary oocytes arrest in Prophase I (Diplotene).
  • Fertilization most commonly occurs in the ampulla of the uterine tube.
  • Corpus luteum produces progesterone to maintain the endometrium for pregnancy.

Practice Questions: Reproductive System

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A female patient presents with hirsutism, amenorrhea, and obesity. What is the most likely diagnosis?

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Flashcards: Reproductive System

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There are three constrictions of the ureter:1 - _____ junction2 - at the Pelvic inlet3 - Ureterovesical junction

TAP TO REVEAL ANSWER

There are three constrictions of the ureter:1 - _____ junction2 - at the Pelvic inlet3 - Ureterovesical junction

Ureteropelvic

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