This video examines the organization of the brachial plexus. The brachial plexus is formed by the union of cervical spinal nerves from C5-C8, and T1. We'll begin by examining the brachial plexus in the axilla and then following it proximally and distally. We reflect the pectoralis major, and the deltoid, and the pectoralis minor to reveal the brachial plexus within the axillary sheath. Important landmarks are the clavicle, the acromioclavicular joint, the acromion, and the coracoid process. In order to facilitate our dissection, we've divided the tendons of the coracobrachialis and the short head of the biceps. When we reflect the coracobrachialis and the short head of the biceps, we identify the musculocutaneous nerve which exits the axillary sheath proximately. We follow the cephalic vein proximately, we see it draining into the axillary vein. As the axillary vein passes deep to the clavicle, it becomes the subclavian vein. Laterally, we identify an artery, which is the subclavian artery proximal to the clavicle and the axillary artery distal. We also see a small branch of the brachial plexus. We open the axillary sheath to reveal the brachial plexus. We continue our dissection of the brachial plexus. For orientation, we show the clavicle and the acromion and the head of the humerus, the coracoid process, and the pectoralis minor. We reflect the pectoralis minor to show the cords of the brachial plexus. For further orientation, we show the axillary vein and the axillary artery. The cords are named for their relationship to the artery. Lateral to the artery, we show the lateral cord. Medial to the artery, we show the medial cor, and we reflect the artery to show the posterior cord. We now follow the terminal branches of the cords of the brachial plexus. We begin with a lateral cord, and we show the cut stump of the lateral pectoral nerve. Moving distally, we show the twig of the musculocutaneous nerve that supplies the coracobrachialis. Continuing distally, we see a branch of the musculocutaneous to the biceps and the terminal cutaneous branch, the lateral cutaneous nerve of the forearm. We show the contribution of the lateral cord to the median nerve. We examine the branches of the medial cord. We identify the medial cord, and we show that it receives a small contribution from the lateral cord. Going distally, we see the contribution of the medial cord to the median nerve. We see the ulnar nerve and the combined trunk of the medial cutaneous nerves of the arm and forearm. We examine branches of the posterior cord. We reflect the lateral and medial cords of the brachial plexus and the axillary vessels to show the posterior cord, which continues distally as the radial nerve. We see it gives off the axillary nerve, and we identify the lower subscapular nerve. We have retracted the cords of the brachial plexus to examine branches of the axillary artery. Proximately, we show the cut stump of the thoracoacromial artery. Distally, we see the common origin of the posterior humeral circumflex artery, and this subscapular artery. We follow the circumflex scapular branch of the subscapular and the thoracodorsal branch. Nearby, we identify the cut stump of the anterior humeral circumflex. We return to the axilla in order to examine the long thoracic nerve, we have retracted the axillary vein and the axillary artery and brachial plexus to show the medial wall of the axilla. Along the medial wall of the axilla, we show the long thoracic nerve, or nerve to the serratus anterior, which is formed by the 5th, 6th, and, 7th cervical spinal nerves. We will now examine the thoracodorsal nerve. For orientation, we show the chest wall and the medial wall of the axilla. We have retracted the axillary artery and vein, and the medial and lateral cords of the brachial plexus to show the posterior cord of the brachial plexus. We see the thoracodorsal nerve branching from the posterior cord and passing distally along the medial wall of the axilla to innervate the deep surface of the latissimus dorsi. As it does so it is accompanied by a branch of the thoracodorsal artery. We emphasize the thoracodorsal nerve and the long thoracic nerve because they're at risk during axillary lymph node dissection. Damage to the long thoracic nerve may produce winged scapula, and damage to the thoracodorsal nerve may produce weak [inaudible] extension in medial rotation of the shoulder.
