Which nerve lies superficially to the extensor retinaculum laterally?

The superficial branch of the radial nerve lies just above the extensor retinaculum, specifically on the lateral aspect of the wrist. This positioning allows the nerve to provide sensory innervation to the skin on the dorsum of the hand. The radial nerve originates in the posterior cord of the brachial plexus and travels down the arm, where it branches into the deep and superficial components. The superficial branch is particularly notable for its sensory function as it fans out into the skin of the lateral aspect of the hand.

In contrast to other nerves mentioned, the median nerve and ulnar nerve are deeper structures in the forearm and do not lie superficially to the extensor retinaculum in the lateral region. The deep branch of the radial nerve, while part of the radial nerve, is responsible for motor innervation to certain muscles and is situated deeper than the superficial branch, lying beneath the retinaculum. This anatomical distinction is crucial for understanding nerve function and potential injury in wrist-related injuries or surgeries.