ulnar nerve

Origin

medial cord of the brachial plexus (C8-T1)

Afferents

• sensory:
  • 4th & 5th fingers & corresponding areas of hand

Efferents

• all of the muscles of the hand not innervated by the median nerve
  • all interosseous muscles
  • thumb adductor
  • flexion of 4th & 5th finger at metacarpophalangeal joint
• muscles of the forearm: ulnar flexion
  • flexor carpi ulnaris
  • ulnar part of the flexor digitorum profundus

Course

• passes inferiorly, posterior to the medial epicondyle of the humerus, down the ulnar side of the anterior compartment of the forearm to the hand

Pathology

injury, ulnar neuropathy:

• elbow (posterior to the medial epicondyle of humerus)
• brachial plexus (less common)
• results in "claw hand"
  • loss of flexion at the metacarpophalangeal joints
  • loss of extension at the interphalangeal joints
• mild trauma produces "crazy bone" or "funny bone" sensation

More general terms

• peripheral nerve

Components

• dorsal digital nerves of ulnar nerve