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Brachial plexus The brachial plexus is an arrangement of nerve fibres, running from the spine, specifically from above the fifth cervical vertebra to underneath the first thoracic vertebra (C5-T1). It proceeds through the neck, the axilla (armpit region) and into the arm. Function The brachial plexus is responsible for cutaneous and muscular innervation of the entire upper limb, with two exceptions: the trapezius muscle innervated by the spinal accessory nerve and an area of skin near the axilla innervated by the intercostobrachialis nerve. This function may be impaired by tumor growth of the Apical region of either Lung. Therefore, brachial plexus lesions can lead to severe functional impairment. Anatomy One can remember the order of brachial plexus elements by way of the mnemonic, "Read The Damn Cadaver Book" - Roots, Trunks, Divisions, Cords, Branches[1] or - Roots, Trunks, Divisions, Cords, Collateral/Pre-terminal Branches, and (Terminal) Branches. The five roots are the five anterior rami of the spinal nerves, after they have given off their segmental supply to the muscles of the neck. These roots merge to form three trunks: o "superior"[2] or "upper" (C5-C6) o "middle"[3] (C7) o "inferior"[4] or "lower" (C8-T1) Each trunk then splits in two, to form six divisions: o anterior division[5] of the superior, middle, and inferior trunks o posterior division[6] of the superior, middle, and inferior trunks These six divisions will regroup to become the three cords. The cords are named by their position in respect to the axillary artery. o The posterior cord is formed from the three posterior divisions of the trunks (C5-T1) o The lateral cord is the anterior divisions from the upper and middle trunks (C5-C7) o The medial cord is simply a continuation of the lower trunk (C8-T1) The branches are listed below. Most branch off of the cords, but a few branch (indicated in italics) directly off of earlier structures. The five in bold are considered "terminal branches". Diagram [edit] Specific branches From Nerve dorsal scapular nerve Roots Muscles rhomboid muscles and roots C5 levator scapulae C5, roots long thoracic nerve serratus anterior C6, C7 superior nerve to the C5, C6 subclavius muscle trunk subclavius superior supraspinatus and suprascapular nerve C5, C6 trunk infraspinatus pectoralis major (by lateral C5, lateral pectoral nerve communicating with the cord C6, C7 medial pectoral nerve) coracobrachialis, lateral musculocutaneous C5, brachialis and biceps cord C6, C7 nerve brachii lateral fibres to the median lateral root of the C5, Cutaneous becomes the lateral cutaneous nerve of the forearm - cord posterior cord posterior cord posterior cord C6, C7 nerve subscapularis (upper C5, C6 part) C6, thoracodorsal nerve latissimus dorsi C7, C8 lower subscapular subscapularis (lower C5, C6 nerve part) and teres major anterior branch: deltoid and a small area of posterior overlying skin C5, C6 axillary nerve cord posterior branch: teres minor and deltoid muscles C5, triceps brachii, anconeus, posterior C6, the extensor muscles of radial nerve cord C7, the forearm, and C8, T1 brachioradialis medial medial pectoral pectoralis major and C8, T1 cord nerve pectoralis minor medial cord medial cord medial cord medial cord median nerve upper subscapular nerve posterior branch becomes upper lateral cutaneous nerve of the arm skin of the posterior arm as the posterior cutaneous nerve of the arm - portions of hand not served by ulnar or radial medial cutaneous front and medial skin C8, T1 nerve of the arm of the arm medial cutaneous medial skin of the C8, T1 nerve of the forearm forearm the skin of the medial flexor carpi ulnaris, the side of the hand and medial 2 bellies of flexor medial one and a half C8, T1 digitorum profundus, fingers on the palmar ulnar nerve most of the small side and medial two muscles of the hand and a half fingers on the dorsal side medial root of the median nerve Additional images fibres to the median C8, T1 nerve