Major contribution to the semen is from:
**Core Concept**
The composition of semen is a complex process involving the contributions of various glands and organs. Semen is a mixture of fluids from the seminal vesicles, prostate gland, and bulbourethral glands, which provides nourishment and protection to sperm during ejaculation.
**Why the Correct Answer is Right**
Seminal vesicles are a pair of glandular structures located behind the bladder that play a crucial role in the production of semen. They secrete a significant amount of fluid into the ejaculatory ducts, which is rich in fructose, ascorbic acid, and other nutrients. These secretions provide energy and protection to sperm, allowing them to survive and fertilize an egg. The seminal vesicles are responsible for approximately 60% of the total volume of semen.
**Why Each Wrong Option is Incorrect**
* **Option A:** While the prostate gland does contribute to semen, its primary function is to secrete an alkaline fluid that helps to neutralize the acidity of the vagina and create a favorable environment for sperm to survive. However, it is not the major contributor to the volume of semen.
* **Option B:** The bulbourethral glands, also known as Cowper's glands, produce a clear pre-ejaculate fluid that helps to lubricate the urethra and prevent bacterial growth. However, their contribution to the overall volume of semen is relatively small.
* **Option C:** The epididymis is a tube-like structure that stores and transports sperm from the testes to the vas deferens, but it does not contribute to the composition of semen.
**Clinical Pearl / High-Yield Fact**
It's worth noting that seminal vesicle secretions are rich in fructose, which provides energy to sperm. This is why seminal vesicle secretions are often used as a diagnostic tool in cases of ejaculatory duct obstruction or other conditions that affect semen production.
**Correct Answer: D. Seminal vesicles. They are the major contributor to the volume of semen.**