Introduction: the ulnar nerve is the largest of the terminal branches of the medial cord of the brachial plexus.
Arm: it passes distally anterior to the triceps muscle on the medial side of the brachial artery near the middle of the arm and descends between it and medial head of the humerus, where it is palpable, to enter the forearm
Forearm: here the nerve passes between the two heads of the flexor carpi ulnaris. It accompanies the ulnar artery near the middle of the forearm and then crosses medial to the artery. It become superficial in the distal part of the forearm covered by fascia and skin. It then pierces the deep fascia and passes superficial to the flexor retinaculum with the ulnar artery.
Surface marking of the nerve is along a drawn line from the medial epicondyle of the humerus to the radial side of the pisiform bone.
1. Articular: passes to the elbow joint
2. Muscular: – to flexor carpi ulnar is
                       – medial half of flexor digitorum profundus.
                       – the interossei, 3rd and 4th lumbricals and adductor pollicis.
3. Cutaneous: to the ulnar side of both aspects of the hand and both surfaces of the ulnar 1½ fingers.
Clinical correlates:
1. If the ulnar nerve is damaged at the wrist all the intrinsic muscles except the radial two Lumbricals are paralysed resulting in claw hand.
2. It may be damaged by fracture of the medial epicondyle of the humerus.