The arm muscles are divided into two separate boxes: the anterior box, in front of the humerus, and the posterior box, behind the humerus.
The anterior chamber of the arm contains three muscles: the biceps brachial, the coracobrachial and the brachial (or anterior brachial). The biceps brachial muscle, made up of two leaders, is not inserted on the humerus but on the scapula at the top and on the radius at the bottom; it allows the supination of the forearm and the bending of the elbow.
The coracobrachial muscle is inserted on the scapula at the top and on the humerus at the bottom; it plays a role in the anterior flexion of the shoulder. The brachial muscle is inserted on the humerus at the top and on the ulna at the bottom; its function is the bending of the elbow.
The posterior lodge of the arm contains a single muscle, the brachial triceps, composed of three muscle leaders; it is inserted at the top on the scapula and humerus, and at the bottom on the ulna; its function is the extension of the elbow.
The forearm has twenty muscles, divided into three boxes, anterior, posterior and lateral.
The anterior (or anteromedial) lodge consists of eight muscles, divided into a superficial and a deep plane. The superficial plane is composed of the pronator round muscles, radial carpal flexor, long palm, superficial finger flexor and ulnar carpal flexor. The deep plane is composed of the deep flexor muscles of the fingers, long thumb flexor and pronator square muscles.
The posterior lodge also has a superficial plane and a deep plane, with eight muscles. The superficial plane is composed of the extensor muscles of the fingers, extensor of the little finger, ulnar extensor of the carpus and anconeal.
The deep plane is composed of the long abductor muscles of the thumb, long extensor of the thumb, short extensor of the thumb and extensor of the index finger.
The lateral compartment has four muscles: brachioradial, long radial carpal extensor, short radial carpal extensor and supinator.