From the Medial cord
1. Medial pectoral nerve (C8, T1): Arises from the medial cord behind the first part of the axillary artery and enters the deep surface of pectoralis minor. It perforates pectoralis minor to enter the pectoralis major muscle.
2. Medial cutaneous nerve of arm (C8, T1): Supplies anterior and medial aspects of the arm.
3. Medial cutaneous nerve of forearm (C8, T1): Supplies the medial aspect of the forearm.
4. Medial root of median nerve (C8, T1) (see median nerve): Crosses the axillary artery to join the lateral head
5. Median nerve (C6, C7, C8, T1):
This arises in the lower axilla by two roots, which clasp the axillary artery. The nerve initially lies anterior to the axillary artery then lateral to it. At the level of the mid-humerus the median nerve crosses the brachial artery, usually anteriorly to lie medial to the artery in the cubital fossa.
It lies on coracobrachialis and then brachialis. It passes beneath the bicipital aponeurosis at the elbow, leaving the cubital fossa between the two heads of pronator teres. It descends deep to the flexor digitorum superficialis on flexor digitorum profundus. Near the wrist it becomes superficial, passing between FDS and flexor carpi radialis. It travels deep to the palmaris longus tendon and enters the carpal tunnel where it divides into a lateral and medial branch. The lateral branch gives off the recurrent (muscular) branch and then breaks up into three palmar digital nerves, two for the thumb and one for the index, the last one also supplying the first lumbrical. The medial branch divides into two common palmar digital nerves for the index, middle and radial half of ring finger and the last one also supplies the second lumbrical. Palmar digital nerves supply not only the whole palmar aspect of the finger but also the distal half of the dorsal aspect of each finger as well. The median nerve does not give off any branches in the arm.
1 It supplies all the flexor muscles of the forearm except flexor carpi ulnaris and the medial half of flexor digitorum profundus (ulnar nerve). It also supplies the thenar eminence and the first and second lumbrical muscles.
2 Anterior interosseous nerve: This arises just below the two heads of pronator teres to run on the interosseous membrane between flexor digitorum profundus and flexor pollicis longus to reach pronator quadratus. It supplies these muscles, except for the medial half of flexor digitorum profundus. It also sends an articular branch to the wrist joint. This nerve does not have a cutaneous branch. Anterior interosseus nerve palsy presents principally as weakness of the thumb and index finger. (OK sign)
3 Palmar cutaneous branch of the median nerve: This arises just proximal to flexor retinaculum and becomes cutaneous between palmaris longus and flexor carpi radialis. It passes superficial to the flexor retinaculum to supply the lateral aspect of the palm (skin). It helps to determine the level of a median nerve injury; numbness over the thenar eminence may indicate a high lesion, whilst intact sensation with loss of function in the recurrent and palmar digital branches may indicate a more distal lesion, e.g. carpal tunnel (this is not entirely reliable owing to the anatomical variations).
4 Recurrent motor (thenar) branch of the median nerve: This supplies abductor pollicis brevis, flexor pollicis brevis and opponens pollicis. It loops around the distal border of flexor retinaculum and enters the thenar muscles.
5 Ulnar nerve (C8, T1): The ulnar nerve arises medial to the axillary artery and continues medial to the brachial artery, lying on coracobrachialis to the midpoint of the humerus where it leaves the anterior compartment by passing posteriorly through the medial intermuscular septum with the superior ulnar collateral artery to enter the posterior compartment of the arm. It runs anterior to the medial head of triceps, passing posterior to the medial humeral epicondyle to enter the forearm between the two heads of flexor carpi ulnaris.
It runs deep to flexor carpi ulnaris on the flexor digitorum profundus with the ulnar artery on its lateral side from one-third of the way down the forearm.
In the distal forearm it becomes superficially covered only by fascia and skin passing superficial to the flexor retinaculum with the ulnar artery. It then passes lateral to the pisiform and grooves the hook of the hamate. The deep branch of the ulnar nerve pierces between abductor digiti minimi and the flexor digiti minimi brevis.
Branches of the ulnar nerve
• No branches in the arm
• Articular branches to elbow joint
• Flexor carpi ulnaris and medial half of flexor digitorum profundus
• Palmar cutaneous branch (skin over hypothenar eminence)
• Dorsal cutaneous branch (medial skin dorsum of hand and 11⁄2 digits).
It arises 5 cm proximal to the wrist, passes deep to FCU onto the medial aspect of te dorsum of the hand
aspect of the dorsum of the hand.
• Superficial branch of the ulnar nerve: supplies palmaris brevis and then
carries on as the superficial palmar branch to innervate the palmar 11⁄2 digits.
• Deep branch of the ulnar nerve: supplies wrist joint, flexor digiti minimi,
abductor digiti minimi, opponens digiti minimi, palmar and dorsal interossei, two medial lumbricals, adductor pollicis and deep head of flexor pollicis brevis.