Step by Step
1
The sperm pathway
Sperm are produced in the seminiferous tubules (within the testes), then mature in the epididymis over about 20 days, gaining motility. From there, sperm travel through the vas deferens, then the ejaculatory duct, then the urethra, and finally exit the body.
2
Accessory glands and their contributions to semen
Seminal vesicles contribute about 60% of semen volume (fructose for energy, prostaglandins, and alkaline fluid). The prostate gland contributes about 25% (citric acid, enzymes, PSA, and alkaline fluid that neutralizes vaginal acidity). The bulbourethral (Cowper's) glands contribute pre-ejaculatory mucus, providing lubrication and neutralizing residual urethral acidity.
3
Why the testes are located in the scrotum
The scrotum keeps the testes about 2-4°C cooler than core body temperature — this cooler temperature is essential for spermatogenesis, which is highly heat-sensitive.
4
Cryptorchidism
Undescended testes (cryptorchidism) impair spermatogenesis, since the testes remain at core body temperature rather than the cooler scrotal temperature needed — this can lead to infertility if not surgically corrected.
Applied Walkthrough
1
Sperm produced in the seminiferous tubules travel to the epididymis, where they spend about 20 days maturing and gaining the motility they'll need to eventually fertilize an egg.
2
From the epididymis, sperm pass through the vas deferens, then the ejaculatory duct, picking up contributions from the seminal vesicles (providing fructose for energy) and the prostate gland (providing alkaline fluid that will help neutralize vaginal acidity) along the way.
3
Just before ejaculation, the bulbourethral glands add lubricating, acid-neutralizing mucus to the urethra, helping create a more hospitable environment for the sperm's exit.
4
In a male with cryptorchidism (undescended testes), this entire spermatogenesis process is impaired from the start, since the testes remain at core body temperature rather than the cooler scrotal environment spermatogenesis requires — a key reason cryptorchidism is corrected surgically when possible.
Exam Application
Exams test whether you can trace the correct sperm pathway (seminiferous tubules → epididymis → vas deferens → ejaculatory duct → urethra), match each accessory gland to its specific contribution to semen, and understand why testicular temperature matters for spermatogenesis.
⚠ Common Trap
The most common trap is confusing which accessory gland contributes the largest volume — the seminal vesicles contribute about 60% of semen volume, more than the prostate's 25%, a detail that's easy to get backward.
✓ Quick Self-Check
1. What is the correct order of the sperm pathway from production to exit?
Seminiferous tubules → epididymis → vas deferens → ejaculatory duct → urethra.
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2. Which accessory gland contributes the largest percentage of semen volume, and what does it provide?
Seminal vesicles, about 60%, providing fructose, prostaglandins, and alkaline fluid.
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3. What does the prostate gland contribute to semen?
Citric acid, enzymes, PSA, and alkaline fluid that neutralizes vaginal acidity.
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4. Why must the testes be cooler than core body temperature?
Because spermatogenesis is heat-sensitive and requires the cooler scrotal environment (2-4°C below core temperature).
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5. What is cryptorchidism, and why does it impair fertility?
Undescended testes; it impairs fertility because the testes remain at core body temperature, too warm for normal spermatogenesis.
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