Final answer:
A vasectomy significantly reduces the percentage of sperm cells in semen because it blocks sperm from entering the ejaculate, although semen volume itself does not decrease. Over time, the sperm are reabsorbed, and semen without sperm is still ejaculated. The correct answer is (b) Decreased sperm cell percentage; increased semen volume.
The correct option is A.
Step-by-step explanation:
The question is regarding the effects of a vasectomy on semen volume and the percentage of sperm cells in the semen. A vasectomy is a form of surgical sterilization in males where the vas deferens are cut or sealed. This prevents sperm from mixing with the ejaculate fluid that forms semen.
Sperm cells constitute a small percentage of the total semen volume, with the seminal fluid added by the seminal vesicles, prostate gland, and bulbourethral glands making up the rest.
After a vasectomy, the testes continue to produce sperm, but these are no longer able to leave the body. Instead, they are reabsorbed over time. Since the semen is still produced by the other glands, the total volume of semen does not change significantly, but it no longer contains sperm. Therefore, the correct answer is (b) Decreased sperm cell percentage; increased semen volume.
It's important to note that it usually takes several months after a vasectomy for all remaining sperm to be ejaculated or reabsorbed. During this time, another method of birth control should be used to ensure effectiveness.
The correct option is A.