Sperm Transport Pathway: From Testes to Ejaculation

Spermatogenesis occurs in the seminiferous tubules of the testes. Mature spermatozoa traverse a defined ductal system, acquiring motility and fertilizing capacity, mixing with glandular secretions to form semen.

Stepwise Pathway

1. Seminiferous tubules (testes): Spermatogenesis (~64 days). Sertoli cells support; Leydig cells produce testosterone.
2. Rete testis → Efferent ductules: Concentration via fluid reabsorption.
3. Epididymis (head → body → tail): 4–6 m coiled tube. Transit 10–14 days. Sperm gain forward motility, fertilization competence. Storage in tail.
4. Vas deferens (ductus deferens): 45 cm muscular tube. Peristaltic propulsion during emission. Ampulla acts as reservoir.
5. Ejaculatory ducts: Formed by union of vas deferens + seminal vesicle ducts. Pass through prostate.
6. Prostatic urethra: Receives prostatic fluid (citrate, zinc, PSA, acid phosphatase; 20–30% semen volume, pH ~6.5).
7. Seminal vesicles (paired): Contribute ~60–70% volume: fructose (energy), prostaglandins, coagulating proteins.
8. Bulbourethral (Cowper's) glands: Pre-ejaculate: mucus lubrication, urethral cleansing.
9. Penile urethra: Expulsion via rhythmic bulbospongiosus contraction (ejaculation).

Key Functional Points

• Epididymal maturation is essential for fertility; obstruction → obstructive azoospermia.
• Seminal fluid provides nutrients, buffers vaginal acidity, promotes capacitation, forms coagulum then liquefaction (PSA).
• Emission (sympathetic, T10–L2) moves sperm to urethra; ejaculation (somatic, S2–S4 via pudendal) expels semen.

Clinical Relevance

• Vasectomy: interrupts vas deferens.
• CBAVD (CFTR mutation): absent vas, seminal vesicles; azoospermia.
• Retrograde ejaculation: bladder neck incompetence (diabetes, α-blockers, surgery).
• Obstructive azoospermia: epididymal blowout, ejaculatory duct cysts, post-infectious.