Branches of the Brachial Plexus Found in the Axilla <br />The nerve to the subclavius (C5 and 6) supplies the subclavius <br />muscle (Figs. 9.15, 9.19, and 9.20). It is important <br />clinically because it may give a contribution (C5) to the <br />phrenic nerve; this branch, when present, is referred to as <br />the accessory phrenic nerve. <br />The long thoracic nerve (C5, 6, and 7) arises from the <br />roots of the brachial plexus in the neck and enters the <br />axilla by passing down over the lateral border of the 1st rib <br />behind the axillary vessels and brachial plexus (Figs. 9.15 <br />and 9.19). It descends over the lateral surface of the serratus <br />anterior muscle, which it supplies. <br />The lateral pectoral nerve arises from the lateral cord of <br />the brachial plexus and supplies the pectoralis major muscle <br />(Figs. 9.13 and 9.20). <br />The musculocutaneous nerve arises from the lateral <br />cord of the brachial plexus, supplies the coracobrachialis <br />muscle, and leaves the axilla by piercing that muscle (Figs. <br />9.13 and 9.20). A summary of the complete distribution of <br />the musculocutaneous nerve is given in Figure 9.22. <br />The lateral root of the median nerve is the direct continuation <br />of the lateral cord of the brachial plexus (Figs. <br />9.13 and 9.19). It is joined by the medial root to form the <br />median nerve trunk, and this passes downward on the lateral <br />side of the axillary artery. The median nerve gives off <br />no branches in the axilla. <br />The medial pectoral nerve arises from the medial cord of <br />the brachial plexus, supplies and pierces the pectoralis minor <br />muscle, and supplies the pectoralis major muscle (Fig. 9.19). <br />The medial cutaneous nerve of the arm (T1) arises <br />from the medial cord of the brachial plexus (Figs. 9.12 and <br />9.20) and is joined by the intercostobrachial nerve (lateral <br />cutaneous branch of the 2nd intercostal nerve). It supplies <br />the skin on the medial side of the arm. <br />The medial cutaneous nerve of the forearm arises from <br />the medial cord of the brachial plexus and descends in front The ulnar nerve (C8 and T1) arises from the medial <br />cord of the brachial plexus and descends in the interval <br />between the axillary artery and vein (Figs. 9.13 and 9.20). <br />The ulnar nerve gives off no branches in the axilla. A summary <br />of the complete distribution of the ulnar nerve is <br />given in Figure 9.23. <br />The medial root of the median nerve arises from the <br />medial cord of the brachial plexus and crosses in front of <br />the third part of the axillary artery to join the lateral root <br />of the median nerve (Figs. 9.13 and 9.20). A summary diagram <br />of the complete distribution of the median nerve is <br />given in Figure 9.22. <br />The upper and lower subscapular nerves arise from the <br />posterior cord of the brachial plexus and supply the upper <br />and lower parts of the subscapularis muscle. In addition, <br />the lower subscapular nerve supplies the teres muscle <br />(Figs. 9.15 and 9.19). <br />The thoracodorsal nerve arises from the posterior cord <br />of the brachial plexus and runs downward to supply the <br />latissimus dorsi muscle (Figs. 9.15 and
