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Nerves of Arm Objectives At the end of the lecture, the student should be able to: 1. 2. 3. 4. To know the nerve supply to arm To know the course of the nerves To know the branches of the nerves To know the clinical correlates of the nerves Following nerve supply upper arm 1. Musculocutaneous nerve Nerve of anterior compartment of arm 2. Radial nerve Nerve of posterior compartment of arm Other nerves are passing through the arm but they are not supplying the arm e.g. Median nerve ulnar nerves Musculocutaneous nerve It is main nerve that supply the front of arm. It is branch of lateral cord of brachial plexus Root value c5, c6, c7 Course In axilla It arises from lateral cord in axilla. In axilla it lies lateral to 3rd part of axillary artery Relation in axilla Anteriorly o pectoralis major Posteriorly o subscapularis Medially o axillary artery o Lateral root of median nerve Laterally o coracobrachialis It leaves the axilla and enters the front of arm by piercing the coracobrachialis. In arm It runs downward and laterally between the biceps and brachialis to reach the lateral side of the tendon of the biceps piercing the deep fascia 2cm above the bent of fore arm and continue as lateral cutaneous nerve of fore arm. Branches Muscular branches o Coracobrachialis o Biceps o Brachialis Cutaneous branches o Through lateral cutaneous nerve of fore arm it supplies the skin of lateral side of fore arm from elbow to wrist. It also supplies elbow joint through its branch to brachialis. Radial nerve Main nerve that supplies the back of the arm It is largest branch of posterior cord of brachial plexus. Root value C5, c6, c7, c8, t1 Course In axilla It lies posterior to third part of axillary artery. It rests on subcapularis, latissimusdorsi from axilla. It passes posteriorly with profunda brachii vessel through lower triangular space, below teres major, between long head of triceps and humerus. It then enters the radial groove with profunda vessel. In radial groove It runs downward and laterally between lateral and medial head of triceps. At the lower end of groove, 5cm below the deltoid tuberosity the nerve pierces the lateral intermuscular septum and passes into anterior compartment of arm. Branches In axilla muscular branches to 1. Long head of triceps 2. Medial head of triceps cutaneous branch 1. Posterior cutaneous nerve of arm. In radial groove Muscular branches 1. Lateral head of triceps 2. Medial head of triceps 3. Anconeus Cutaneous branches 1. Lower lateral cutaneous nerve of arm 2. Posterior cutaneous nerve of fore arm Articular branch 1. To elbow joint Clinical correlates Radial nerve is very commonly damaged in the region of radial groove. Cause of injury -intramuscular injection in triceps instead of deltoid -fracture of shaft of humerus Clinical features -weakness or loss of power of extension at wrist (wrist drop) -sensory loss over back of lateral part of the dorsum of the hand