human anatomy Arm Structures Passing through the Anterior Fascial Compartment Brachial Artery The brachial artery (Figs. 9.42 and 9.43) begins at the lower border of the teres major muscle as a continuation of the axillary artery. It provides the main arterial supply to the arm (Fig. 9.42). It terminates opposite the neck of the radius by dividing into the radial and ulnar arteries. Relations ■■ Anteriorly: The vessel is superficial and is overlapped from the lateral side by the coracobrachialis and biceps. The medial cutaneous nerve of the forearm lies in front of the upper part; the median nerve crosses its middle part; and the bicipital aponeurosis crosses its lower part (Fig. 9.43). ■■ Posteriorly: The artery lies on the triceps, the coracobrachialis insertion, and the brachialis (Fig. 9.43). ■■ Medially: The ulnar nerve and the basilic vein in the upper part of the arm; in the lower part of the arm, the median nerve lies on its medial side (Fig. 9.43). ■■ Laterally: The median nerve and the coracobrachialis and biceps muscles above; the tendon of the biceps lies lateral to the artery in the lower part of its course (Fig. 9.43). Branches ■■ Muscular branches to the anterior compartment of the upper arm ■■ The nutrient artery to the humerus ■■ The profunda artery arises near the beginning of the brachial artery and follows the radial nerve into the spiral groove of the humerus (Fig. 9.45). ■■ The superior ulnar collateral artery arises near the middle of the upper arm and follows the ulnar nerve (Fig. 9.45). ■■ The inferior ulnar collateral artery arises near the termination of the artery and takes part in the anastomosis around the elbow joint (Fig. 9.45). Musculocutaneous Nerve The origin of the musculocutaneous nerve from the lateral cord of the brachial plexus (C5, 6, and 7) in the axilla is described on page 352. It runs downward and laterally, pierces the coracobrachialis muscle (Fig. 9.15), and then passes downward between the biceps and brachialis muscles (Fig. 9.43). It appears at the lateral margin of the biceps tendon and pierces the deep fascia just above the elbow. It runs down the lateral aspect of the forearm as the lateral cutaneous nerve of the forearm Median Nerve The origin of the median nerve from the medial and lateral cords of the brachial plexus in the axilla is described on page 352. It runs downward on the lateral side of the brachial artery (Fig. 9.43). Halfway down the upper arm, it crosses the brachial artery and continues downward on its medial side. Ulnar Nerve The origin of the ulnar nerve from the medial cord of the brachial plexus in the axilla is described on page 353. It runs downward on the medial side of the brachial artery as far as the middle of the arm (Fig. 9.43). Here, at the insertion of the coracobrachialis, the nerve
