**Core Concept**
The obturator foramen is a significant anatomical structure that allows various nerves, vessels, and ligaments to pass through it, connecting the pelvic cavity to the thigh. The obturator foramen is a large opening in the pelvic bone that transmits essential structures, enabling communication between the pelvic and lower limb regions.

**Why the Correct Answer is Right**
Internal pudendal vessels, which supply the external genitalia, do not pass through the obturator foramen. Instead, they exit the pelvis through the greater sciatic foramen, below the piriformis muscle, and then re-enter the pelvic cavity through the lesser sciatic foramen. This unique pathway avoids compression of the internal pudendal vessels by the obturator internus muscle.

**Why Each Wrong Option is Incorrect**
**Option A:** The obturator nerve, a branch of the lumbar plexus, does indeed pass through the obturator foramen to innervate the adductor muscles of the thigh. This nerve is essential for limb function and proprioception.
**Option B:** The obturator artery, a branch of the internal iliac artery, also traverses the obturator foramen to supply the thigh muscles and bone. Its passage through the foramen is crucial for the vascular supply of the lower limb.
**Option C:** The obturator vein, which accompanies the obturator artery, also passes through the obturator foramen, facilitating venous drainage of the thigh.

**Clinical Pearl / High-Yield Fact**
Recall that the obturator foramen transmits vital structures, including the obturator nerve, artery, and vein, which are essential for thigh function and limb vascular supply. Familiarize yourself with the pathways of these structures to avoid confusion during clinical exams and practical procedures.

✓ Correct Answer: D. Internal pudendal vessels.