**Core Concept**
The procedure of vasectomy involves interrupting the passage of sperm through the vas deferens, which is a crucial part of the male reproductive system. The vas deferens is a muscular tube that transports sperm from the epididymis to the ejaculatory ducts.

**Why the Correct Answer is Right**
During a vasectomy, the surgeon ligates (ties off) the vas deferens to prevent sperm from entering the ejaculatory ducts. This is typically done by making a small incision in the scrotum and cutting the vas deferens, then ligating it with a suture. The ligature prevents sperm from passing through the vas deferens, thereby preventing fertilization.

**Why Each Wrong Option is Incorrect**
**Option A:** The seminal vesicles are not involved in the vasectomy procedure. They are glandular structures that produce a significant portion of the fluid that makes up semen, but they are not directly involved in the transport of sperm.
**Option B:** The epididymis is a structure where sperm mature and are stored, but it is not the target of the vasectomy procedure.
**Option C:** The ejaculatory ducts are the structures where sperm enter the urethra to be ejaculated, but they are not the site of the vasectomy procedure.

**Clinical Pearl / High-Yield Fact**
It's essential to note that vasectomy is a permanent form of birth control, and it's crucial for the patient to understand the risks and benefits before undergoing the procedure.

**Correct Answer: D. The vas deferens is surgically ligated during a vasectomy.**