Now we’ll look at the three main nerves of the forearm and hand, the radial, the median and the ulnar. We’ll go back to where we last saw the radial nerve.
Here we are at the elbow, with brachioradialis retracted. Here’s the radial nerve. It diivides, as we saw, into a superficial and a deep branch. The superficial branch runs down the forearm deep to brachioradialis. In the distal forearm it passes backwards and emerges from beneath the brachioradialis tendon Approaching the wrist it crosses over extensor pollicis brevis, and longus, to reach the back of the hand.
The superficial branch of the radial is entirely a sensory nerve. It supplies, usually, the radial half of the back of the hand, the back of the thumb, and part of the back of the index.
The deep branch of the radial nerve, also known as the posterior interosseous nerve, is a motor nerve. It passes through the supinator, and emerges here, deep to extensor digitorum. It breaks up into several branches. Between them these supply extensor carpi ulnaris, extensor digitorum and the other two finger extensors, and these three long thumb muscles, abductor pollicis longus, and extensor pollicis brevis, and longus.