<P> The first four compartments are located in the grooves present on the dorsum of inferior side of radius while the 5th compartment is in between radius and ulna . The 6th compartment is in the groove on the dorsum of inferior side of ulna . </P> <P> The muscles of the hand are innervated by the radial, median, and ulnar nerves . </P> <P> The radial nerve innervates the finger extensors and the thumb abductor; that is, the muscles that extend at the wrist and metacarpophalangeal joints (knuckles) and abduct and extend the thumb . The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, the first and second lumbrical . The ulnar nerve innervates the remaining intrinsic muscles of the hand . </P> <P> All muscles of the hand are innervated by the brachial plexus (C5--T1) and can be classified by innervation: </P>

The extrinsic flexor muscles of the hand are