What is a branch of the lumbar plexus?

The femoral nerve is indeed a branch of the lumbar plexus, which is crucial for motor and sensory innervation in the lower limb. It arises from the nerve roots of L2, L3, and L4 and mainly innervates the quadriceps muscle, providing motor function for knee extension. Additionally, it contributes to sensory innervation for the anterior thigh and part of the medial leg through the saphenous nerve, a branch of the femoral nerve.

In contrast, the other listed nerves originate from different sections of the nervous system. The pudendal nerve, though involved in pelvic innervation, primarily arises from the sacral plexus. Cranial nerve XI, known as the accessory nerve, is responsible for neck and shoulder movement and also does not originate from the lumbar plexus, as it emerges from the brainstem. The radial nerve, which is responsible for innervating muscles in the posterior arm and forearm, branches from the brachial plexus rather than the lumbar plexus. Hence, the femoral nerve stands out as the correct choice, demonstrating its crucial role in the anatomy and function of the lower extremity based on its origin and course within the lumbar plexus.