The Deltoid Muscles of the Arm

The arms have several muscles. The wrist flexors, for example, are on the front of the forearm and include the flexor carpi radialis and ulnaris. The flexor pollicis longus, palmaris longus, and digitorum profundus are also part of this group. In addition to these muscles, the arm also has a number of pronator quadratus and supinator teres muscles.

Pectoralis major

The Pectoralis major muscle originates on the anterior surface of the clavicle and is connected to the sternocostal nerve through the medial cord of the brachial plexus. The muscle receives arterial blood supply from the thoracoacromal artery and the internal thoracic artery. Pectoralis major is the largest muscle in the arm. Its function depends on the head of the muscle involved.


The deltoid muscles of the arm allow you to move your arm in different directions. They also stabilize the shoulder joint and protect it from injury. Performing repetitive overhead movements may cause deltoid muscle injury. While many deltoid injuries heal on their own, you should seek medical attention if you’re unsure of their cause. Here are some causes and treatment options. Listed below are some common deltoid muscle injuries.

Rotator cuff

The four rotator cuff muscles in the arm work together to hold the upper arm securely in the shoulder and help it do a wide variety of arm motions. The tendons in the rotator cuff include the supraspinatus, infraspinatus, subscapularis, and teres minor. A tear in any one of these tendons can lead to a tear or a degeneration of the tendon. Fortunately, most rotator cuff tears can be treated conservatively and a full recovery can be expected.

Pronator teres

The pronator teres muscles in the forearm originate just below the infraspinatous muscle. They originate on the anterior surface of the ulna and travel up the shaft to attach to the lower portion of the greater tuberosity. The muscles are innervated by the median nerve and anterior interosseous branch. During flexion and abduction exercises, you can engage these muscles to prevent pronation.

Flexor carpi ulnaris

The flexor carpi ulnaris muscle is a member of the common flexor belly/tendon. It attaches to the pisiform bone and the hook of the hamate. The muscle performs wrist flexion and abduction. The ulnar artery passes through its medial border. Its origins are from the olecranon of the ulna and the medial epicondyle of the humerus.

triceps brachii

The triceps brachii are two muscles in the posterior compartment of the upper arm. They function to straighten the bent arm. Their name comes from the three bundles of muscle fibers they have attached to the radial and axillary nerves. Because they are responsible for straightening the arm, a hit to these muscles will indicate proper function of the nerves in the arm.

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