**Core Concept**
The lesser sciatic foramen is an anatomical passage in the pelvis that allows various nerves and vessels to pass between the gluteal region and the perineum. Understanding the contents of this foramen is crucial for identifying the correct answer.

**Why the Correct Answer is Right**
The inferior gluteal vessels, which include the inferior gluteal artery and vein, primarily supply the gluteal region and do not pass through the lesser sciatic foramen. In contrast, the internal pudendal vessels (superficial and deep branches of the internal pudendal artery and vein) and the pudendal nerve, which provides motor and sensory innervation to the perineum, do pass through the lesser sciatic foramen. The nerve to obturator internus, which innervates the obturator internus muscle, also traverses this foramen.

**Why Each Wrong Option is Incorrect**
**Option B:** The internal pudendal vessels are indeed a content of the lesser sciatic foramen, as they supply the perineal region.
**Option C:** The pudendal nerve, responsible for innervating the perineal muscles, does pass through the lesser sciatic foramen.
**Option D:** The nerve to obturator internus, which innervates the obturator internus muscle, traverses the lesser sciatic foramen.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the contents of the lesser sciatic foramen are primarily related to the perineal region, including the pudendal nerve, internal pudendal vessels, and nerve to obturator internus, whereas the superior gluteal vessels pass through the greater sciatic foramen.

**✓ Correct Answer: A. Inferior gluteal vessels**