The Brachial Plexus C5-C8, T1

• Anterior divisions supply the flexor (anterior) parts of the upper limb

• Posterior divisions supply the extensor (posterior) parts of the upper limb

• Each cord divides into two terminal branches

• Supraclavicular part (rami and trunks with their branches) is in the posterior triangle of the neck.

  • Branches:

    • Dorsal scapular nerve C4/5 – Rhomboid muscle

    • Long thoracic nerve C5, 6, 7 – Serratus anterior

    • Nerve to subclavius C5 – Subclavius muscle

    • Suprascapular nerve C5,6- supraspinatus and infraspinatus and shoulder joint

• Infraclavicular part (cords and their branches) is in the axilla.

• Lateral cord branches

  • Lateral pectoral nerve C5,6,7 – Pec major

    • *Note this nerve runs deep to pec major and medial to the medial pectoral nerve.

  • Musculocutaneous nerve C5, 6, 7 – Coracobrachialis, biceps brachii, and brachialis. Proximal to elbow joint this nerve pierces the deep fascia and becomes superficial. From here it is called the lateral antebrachial cutaneous nerve, and supplies skin on lateral aspect of the forearm.

  • Lateral root of median nerve – joined by medial root of median nerve, lateral to axillary artery to form the median nerve. Median nerve supplies flexor muscles in forearm, except flexor carpi ulnaris, and the skin on the hand.

• Medial cord branches

  • Medial pectoral nerve C8, T1- Pec minor and part of pec major.

  • Medial brachial cutaneous nerve C8, T1 – supplies skin over medial surface of arm and proximal surface of forearm.

  • Medial antebrachial cutaneous nerve C8, T1 – runs between axillary artery and vein, supplies skin over medial surface of forearm.

  • Ulnar nerve C8, T1 – Supplies one and one half muscles in forearm, most small muscles in hand and some skin.

• Posterior cord branches – supply muscles that extend joints of upper limb, and supply cutaneous branches to extensor surface.

  • Upper subscapular nerve C5,6 – Supplies subscapularis

  • Thoracodorsal nerve C6, 7, 8 – supplies lat dorsi

  • Lower subscapular nerve C5, 6 – Teres major, and supplies a branch to subscapularis

  • Axillary nerve C5,6- Passes through the quadrangular space and winds round surgical neck of humerus to supply teres minor and deltoid. Ends as the upper lateral brachial cutaneous nerve and supplies skin over inferior half of deltoid and adjacent areas.

  • Radial nerve C5,6,7,8, T1 – major nerve supply to extensor muscles of upper limn, and cutaneous sensation to skin overlying extensor region, including hand. Leaves axilla between long and medial head of triceps, and enters radial groove in humerus. Give branches to triceps, anconeus, brachioradialis and extensor muscles of forearm.

• Carpal tunnel syndrome:

• Compression of median nerve as passes through the carpal tunnel at the wrist. The carpal tunnel is formed by the space between the transverse carpal ligament and the carpal bones.

• Presents with pain and/or paraesthesia in the median nerve distribution (lateral 3 and a half fingers). Symptoms radiate proximally towards the elbow. Often worse at night, and classically keeps patient awake.

• Ulnar nerve entrapment:

• Compressed as it passes behind medial epicondyle or through Guyon’s canal at the wrist.

• Pain and/or paraesthesia in medial side of elbow, which radiates to the medial forearm and the ulnar distribution in the hand (medial one and a half fingers).

• Radial nerve injuries:

• Radial nerve compression – ‘Saturday night palsy’

• Also injured in fractures of the humerus

• Wrist extensors paralysed resulting in wrist drop

• Nerve injury in axilla also leads to paralysis of triceps

Category: Anatomy Notes