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Nerve Infraclavicular branches Lateral pectoral Musculocutaneous Median Medial pectoral Medial cutaneous nerve of arm Medial cutaneous nerve of forearm Ulnar Upper subscapular Lower subscapular Thoracodorsal Axillary Radial Origin Side branch of lateral cord, receiving fibers from C5, C6, and C7 Ter...

Nerve Infraclavicular branches Lateral pectoral Musculocutaneous Median Medial pectoral Medial cutaneous nerve of arm Medial cutaneous nerve of forearm Ulnar Upper subscapular Lower subscapular Thoracodorsal Axillary Radial Origin Side branch of lateral cord, receiving fibers from C5, C6, and C7 Terminal branch of lateral cord, receiving fibers from C5-C7 Lateral root of median nerve is a terminal branch of lateral cord (C6, C7). Medial root of median nerve is a terminal branch of medial cord (C8, T1). Side branches of medial cord, receiving fibers from C8 and T1 Larger terminal branch of medial cord, receiving fibers from C8, T1, and often C7 Side branch of posterior cord, receiving fibers from C5 Side branch of posterior cord, receiving fibers from C6 Side branch of posterior cord, receiving fibers from C6, C7, and C8 Terminal branch of posterior cord, receiving fibers from C5 and C6 Larger terminal branch of posterior cord (largest branch of plexus), receiving fibers from C5-T1 Course Pierces costocoracoid membrane to reach deep surface of pectoral muscles; a com- municating branch to the medial pectoral nerve passes anterior to axillary artery and vein Exits axilla by piercing coracobrachialis (Fig. 3.43); descends between biceps brachii and brachialis (Figs. 3.47B and 3.48), supplying both; continues as lateral cutaneous nerve of forearm Lateral and medial roots merge to form median nerve lateral to axillary artery; descends through arm adjacent to brachial artery, with nerve gradually crossing anterior to artery to lie medial to artery in cubital fossa (see Fig. 3.53). Passes between axillary artery and vein; then pierces pectoralis minor and enters deep surface of pectoralis major; although it is called medial for its origin from medial cord, it lies lateral to lateral pectoral nerve Smallest nerve of plexus; runs along medial side of axillary and brachial veins; communicates with intercostobrachial nerve Initially runs with ulnar nerve (with which it may be confused) but pierces deep fascia with basilic vein and enters subcutaneous tissue, dividing into anterior and posterior branches Descends medial arm; passes posterior to medial epicondyle of humerus; then descends ulnar aspect of forearm to hand (Figs. 3.46C and 3.47A) Passes posteriorly, entering subscapularis directly Passes inferolaterally, deep to subscapular artery and vein Arises between upper and lower sub- scapular nerves and runs inferolaterally along posterior axillary wall to apical part of latissimus dorsi Exits axillary fossa posteriorly, passing through quadrangular space with posterior circumflex humeral artery (Fig. 3.48); gives rise to superior lateral brachial cutaneous nerve; then winds around surgical neck of humerus deep to deltoid (Fig. 3.46D) Exits axillary fossa posterior to axillary artery; passes posterior to humerus in radial groove with deep brachial artery, between lateral and medial heads of triceps; perforates lateral intermuscular septum; enters cubital fossa, dividing into superficial (cutaneous) and deep (motor) radial nerves (Fig. 3.46D) Structures Innervated Primarily pectoralis major; but some lateral pectoral nerve fibers pass to pectoralis minor via branch to medial pectoral nerve (Fig. 3.46A) Muscles of anterior compartment of arm (coracobrachialis, biceps brachii and brachialis) (Fig. 3.46B); skin of lateral aspect of forearm Muscles of anterior forearm compart- ment (except for flexor carpi ulnaris and ulnar half of flexor digitorum profundus), five intrinsic muscles in thenar half of palm and palmar skin (Fig. 3.46B) Pectoralis minor and sternocostal part of pectoralis major Skin of medial side of arm, as far dis- tal as medial epicondyle of humerus and olecranon of ulna Skin of medial side of forearm, as far distal as wrist Flexor carpi ulnaris and ulnar half of flexor digitorum profundus (forearm); most intrinsic muscles of hand; skin of hand medial to axial line of digit 4 Superior portion of subscapularis Inferior portion of subscapularis and teres major Latissimus dorsi Glenohumeral (shoulder) joint; teres minor and deltoid muscles (Fig. 3.46D); skin of superolateral arm (over inferior part of deltoid) All muscles of posterior com- partments of arm and forearm (Fig. 3.46D); skin of posterior and inferolateral arm, posterior forearm, and dorsum of hand lateral to axial line of digit 4