The upper extremities consist of the hand, arm, and shoulder.
The hands contain more tendons than muscles. These tendons attach the forearm muscles to the bones of the hand. Some of these muscles include the finger flexors, finger extensors, opponens pollicis, flexor pollicis brevis, lumbricales, palmar interossei, dorsal interossei, abductor digiti minimi, opponens digiti minimi, flexor digiti minimi brevis, abductor pollicis brevis, and adductor pollicis.
The muscles of the forearm flex and extend the forearm. The wrist flexors include the flexor carpi ulnaris, flexor carpi radialis, palmaris longus, and pronator teres, they flex the wrist. The wrist extensors include the extensor carpi ulnaris, extensor carpi radialis longus, and extensor carpi radialis brevis, they extend the wrist. The brachioradialis flexes the forearm. The extensor digitorum extends the forearm. The anconeus pronates and supinates the forearm.
The upper arm has muscles that flex and extend the arm. The biceps brachii on the anterior side of the arm, flexes the arm. The triceps brachii on the posterior side of the arm, extends the arm. The brachialis helps flex the arm.
The shoulder has quite a few muscles in and around the joint. The rotator cuff muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis. The supraspinatus, found under the trapezius, abducts the shoulder and is the most frequently injured rotator cuff muscle. The infraspinatus, on top of the scapula, laterally rotates the arm like a tennis back hand swing. The teres minor, lateral to the scapula, laterally rotates the shoulder and adducts the shoulder. The subscapularis, under the scapula, medially rotates the shoulder and stabilizes the shoulder. The teres major, below the teres minor, also adducts and medially rotates the arm. The deltoideus, on the top of the shoulder, rotates, abducts and extends the arm. The pectoralis major, in the chest, adducts and medially rotates the arm. The latissiumus dorsi, in the back, extends, adducts, and medially rotates the arm.