A client asks a nurse about the function of the fluid produced by the bulbourethral glands. Which of the following is the most accurate explanation?

Bulbourethral gland secretion plays a critical role in urethral pH regulation and lubrication during sexual arousal. The Cowper’s glands, located inferior to the prostate, secrete a clear, mucous-like fluid that neutralizes acidic urine residue in the penile urethra and provides lubrication for sperm transport. This secretion precedes ejaculation and protects sperm from damage. Normal semen pH ranges from 7.2 to 8.0, and optimal sperm motility requires this alkaline environment.

Rationale for correct answers

B. The bulbourethral glands secrete a pre-ejaculate fluid that serves to neutralize residual acidic urine in the urethra, creating an alkaline path for sperm passage. This secretion also lubricates the penile urethra, reducing friction and aiding sperm viability during ejaculation.

Rationale for incorrect answers

A. Fructose is secreted by the seminal vesicles, not the bulbourethral glands. Seminal fluid provides an energy source for sperm via fructose, but this is unrelated to bulbourethral gland function.

C. Coagulation of semen is facilitated by fibrinogen-like proteins in seminal vesicle fluid. This process helps semen temporarily coagulate post-ejaculation, but the bulbourethral glands are not involved in this mechanism.

D. Prostate-specific antigen (PSA) is secreted by the prostate gland, not the bulbourethral glands. PSA helps liquefy semen after coagulation to enable sperm motility, which occurs post-ejaculation.

Take home points

• Bulbourethral gland fluid neutralizes urethral acidity and provides lubrication.
• Fructose in semen comes from seminal vesicles, not bulbourethral glands.
• PSA is a prostate secretion, not from bulbourethral glands.
• Semen coagulation and liquefaction involve different glandular secretions.

Scrotal thermoregulation is vital for maintaining the optimal temperature required for normal spermatogenesis, which occurs 2°C to 4°C (3E.6°F to 39.2°F) below core body temperature. The cremaster muscle, a skeletal muscle derived from the internal oblique, elevates the testes in response to cold, physical stimulation, or threat. This action reduces heat loss, supporting sperm viability. Normal testicular volume is 12 to 30 mL, and normal semen motility requires temperatures below 35°C (95°F) to prevent DNA damage and impaired motility.

Rationale for correct answers

B. The cremaster muscle contracts reflexively to elevate the testes toward the abdominal wall in response to cold temperatures or tactile stimulation, conserving heat and optimizing the temperature for spermatogenesis. This reflex is especially active in cold environments and is essential for protecting sperm development.

Rationale for incorrect answers

A. The dartos muscle is a layer of smooth muscle in the scrotal wall that contracts to wrinkle the scrotal skin, reducing surface area and minimizing heat loss. However, it does not pull the testes upward toward the body like the cremaster muscle.

C. The bulbospongiosus muscle is a perineal muscle involved in emptying the urethra after urination and aiding ejaculation. It has no role in thermoregulation or testicular elevation.

D. The ischiocavernosus muscle compresses the crus of the penis and helps maintain erection. It is unrelated to testicular temperature regulation and has no influence on scrotal positioning.

Take home points

• The cremaster muscle elevates testes to conserve heat.
• Dartos muscle wrinkles the scrotum to reduce heat loss.
• Perineal muscles like bulbospongiosus are not involved in thermoregulation.
• Proper scrotal temperature is critical for healthy sperm production.