Which nerve runs medial to lateral between the greater and lesser sciatic foramen?

The pudendal nerve is the correct choice because it has a distinctive pathway that allows it to run between the greater and lesser sciatic foramina. Specifically, it exits the pelvis through the greater sciatic foramen, travels around the ischial spine, and then enters the perineum via the lesser sciatic foramen. This nerve is crucial for innervating the structures in the pelvic region, notably the perineal muscles and the external genitalia. Its position, being situated medial to the sciatic nerve and lateral to the internal pudendal vessels, supports its identification as the correct nerve in this context.

In contrast, the sciatic nerve primarily runs beneath the piriformis muscle, and it does not traverse between these foramina. The superior gluteal nerve exits the pelvis above the piriformis muscle through the greater sciatic foramen, while the inferior gluteal nerve exits below it. Thus, neither of these nerves runs in the specified pathway between the greater and lesser sciatic foramina.