The upper arm has two muscle compartments: the anterior, which includes the biceps, and the posterior, which includes the triceps muscle.

The forearm has two major compartments: the anterior containing the flexor muscles, and the posterior containing the extensor muscles. The mobile wad creates the third compartment.

The upper extremity is perfused by branches from the deep and superficial brachial artery. The proximal brachial artery lies in the groove between the biceps and triceps muscles. Distally, it courses in front of the humerus. At the antecubital fossa, it runs deep to the bicipital aponeurosis and bifurcates into the radial and ulnar arteries, just below the elbow. The artery is surrounded by the two concomitant brachial veins, which run on either side of the artery.

The profunda brachial artery is a large branch arising from the proximal brachial artery distal to the teres major muscle and follows the radial nerve closely. It provides collateral circulation to the lower arm.

The basilic vein courses in the subcutaneous tissue in the medial aspect of the lower arm. At the midpoint, it penetrates the fascia to join one of the brachial veins.

The cephalic vein is entirely in the subcutaneous tissues, courses in the deltopectoral groove, and empties into the junction of the brachial and axillary veins.

In the upper arm, the median nerve lies in front of the brachial artery. It then crosses over the artery midway down the upper arm, where distally it lies posteromedial to the artery.

The ulnar nerve is behind the artery in the upper half of the arm. Midway down the arm, it pierces the intermuscular septum and courses more posteriorly, away from the artery, behind the medial epicondyle.