Question

The prostatic fluid forms about.... of total volume of semen.
A. $60\%$
B. $50\%$
C. $40\%$
D. $30\%$

Answer 1

Hint: Semen represents the mixture of sperms and the seminal plasma. Seminal plasma includes the secretions from the male accessory sex glands. Around $96\%$ of the semen volume is contributed by these glands while sperms and testicular secretions make only $4\%$ of it.

Complete answer:
Male reproductive system includes a pair of testes, accessory sex glands, ducts, and the supporting structures. Testes are the primary sex organs of males and are the site for the production of sperms, the male gametes. Accessory sex glands secrete most of the liquid part of the semen. The male accessory sex glands are paired seminal vesicles, a prostate, and paired bulbourethral glands.

Seminal vesicles secrete an alkaline fluid that is rich in fructose. Fructose serves as a source of energy for sperms. Therefore, secretion from the seminal vesicles maintains the mobility and viability of sperms.

The bulbourethral glands secrete an alkaline fluid to neutralize the acidic environment of the urethra. It is also rich in mucus and lubricates the tip of the penis during sexual intercourse.

The prostate gland is walnut-shaped and secretes acidic fluid. The enzymes present in the secretion of this gland break down the clotting proteins present in the semen and facilitate the smooth movement of sperms within the female reproductive tract. It makes $30\%$ of the total volume of semen.

Hence, the correct answer is option (D).

Note: Most of the volume of seminal plasma is contributed by seminal vesicles as their secretion carries the source of ATP for sperms. The seminal vesicles produce about $65\%$ of the semen while the prostate gland contributes about $30\%$. The bulbourethral glands contribute less than $1\%$ of the semen.