The supraclavicular part gives rise to motor nerves that innervate the muscles of theshoulder girdle.
The following nerves run to the posteriorand lateral surfaces of the thorax: thedorsalscapular nerve (A1) (C5) to the scapularmuscle (C2) and to the lesser (C3) and greater (C4) rhomboid muscles; the longthoracic nerve (A5) (C5 – C7), the branches ofwhich terminate at the lateral thoracic wall in the peaks of the anterior serratus muscle (B6); and the thoracodorsal nerve (A7) (C7, C8), which supplies the latissimus dorsi muscle (C8). The muscles of the shoulder blade are innervated at the posterior surface of the shoulder blade (supraspinous muscle [C9] and infraspinous muscle [C10]) by the suprascapular nerve (A11) (C5, C6), and at theanterior surface by the subscapular nerve (A12) (C5 – C7), which extend to the sub-scapular muscle and the greater teres muscle (C13).
The following nerves reach the anterior sur-face of the thorax: thesubclavius nerve(A14)(C4 – C6) (to the subclavius muscle [B15), the lateral pectoral nerve (A16) (C5 – C7) and the medial pectoral nerve (A17) (C7 – T1), which supply the greater (B18) and lesser (B19) pectoral muscles.
Clinical Note: Injury to the supraclavicularpart leads to paralysis of the muscles of the shoulder girdle and makes it impossible to raise the arm. This type of upper brachial plexus paraly-sis (Erb’s palsy) may be caused by dislocation ofthe shoulder joint during birth, or through im-proper positioning of the arm during anesthesia. Injury to the infraclavicular part of the brachial plexus results in lower brachial plexus paralysis(Klumpke ’s palsy), which predominantly involves the small muscles of the hand and possibly also the flexor muscles of the forearm.