Which male structure secretes PSA?

Seminal vesicle fluidis an alkaline secretion constituting about 60–70% of semen volume, rich in fructose, prostaglandins, and clotting proteins. Fructoseserves as the primary energy substrate for sperm motility by entering glycolysis within sperm cells. Normal seminal plasma fructose concentration is approximately 11–15 mmol/L. The alkaline pH (7.2–8.0) neutralizes vaginal acidity, enhancing sperm survival. Prostaglandins promote cervical mucus thinning and induce reverse peristalsis in the female reproductive tract to aid sperm transport.

Rationale for correct answers

B.Fructose in seminal vesicle fluid is the main nutrient metabolized by spermatozoa to generate ATP for motility and fertilization capability.

Rationale for incorrect answers

A.Glucose is not the predominant sugar in seminal vesicle fluid; while sperm can metabolize glucose, seminal vesicles specifically secrete fructose as their carbohydrate source.

C.Galactose is not a major component of seminal plasma; it is not secreted by seminal vesicles and has no primary role in fueling sperm.

D.Citrate is present in prostatic fluid, functioning mainly as a pH buffer and nutrient, but is not the main motility fuel in seminal vesicle secretion.

Take home points

• Seminal vesicles secrete fructose as the primary sperm energy source.
• Fructose concentration in seminal fluid can be a marker of seminal vesicle function.
• Prostatic fluid contains citrate, not fructose.
• Alkalinity of seminal fluid helps sperm survive in acidic vaginal environment.

Prostate glandis a fibromuscular exocrine glandencircling the proximal urethra, located inferior to the bladder. It secretes a slightly acidic fluid (pH 6.5–6.7) containing prostate-specific antigen(PSA), citrate, and proteolytic enzymes. PSA is a serine protease that liquefies semen by breaking down seminogelin, aiding sperm motility. Normal serum PSA in healthy adult males is ≤4.0 ng/mL. PSA levels can rise in benign prostatic hyperplasia, prostatitis, and prostate cancer, making it a useful but non-specific screening marker.

Rationale for correct answers

A.The prostate gland secretes PSA into seminal fluid to facilitate semen liquefaction after ejaculation, enhancing sperm motility.

Rationale for incorrect answers

B.The bulbourethral glands (Cowper’s glands) secrete pre-ejaculatory alkaline mucus to neutralize acidic urine residues in the urethra, not PSA.

C.The seminal vesicles secrete alkaline fluid rich in fructose and prostaglandins, but they do not produce PSA.

D.The epididymis functions in sperm maturation, storage, and reabsorption of unused sperm, with no secretory role in PSA production.

Take home points

• PSA is secreted by the prostate gland into seminal fluid.
• PSA liquefies semen for improved sperm motility.
• Serum PSA is a non-specific marker for prostate disorders.
• Seminal vesicles and bulbourethral glands do not secrete PSA.