Muscles of the Upper Limb

The motions of the shoulder joint are controlled by muscles which originate on the anterior and posterior chest wall, and by muscles which originate superior to the scapula and clavicle. The principal muscles which originate on the anterior chest wall are pectoralis major and pectoralis minor. Pectoralis major originates along the inferior margin of the medial clavicle, as well as the costal cartilages and the sternum. It inserts on the humerus, and so draws the humerus anterior and rotates it medially. Pectoralis minor originates inferior and deep to the pectoralis major. It inserts on the coracoid process of the scapula and so helps to draw the shoulders forward. The actions of pectoralis major and minor are balanced by the trapezius and latissimus dorsi muscles. These muscles originate along the length of the cervical, thoracic and lumbar spine and so help to draw the shoulders backwards.

The humerus is abducted by the supraspinatus and deltoid muscles. The deltoid originates on the lateral clavicle and acromion process of the scapula. The supraspinatus originates along the superior edge of the spine of the scapula. Both deltoid and supraspinatus insert on the upper humerus. The supraspinatus is one of four muscles known collectively as the rotator cuff muscles. The other three muscles of this group are the infraspinatus, teres minor and subscapularis. Infraspinatus originates inferior to the spine of the scapula and teres minor originates on the lateral margin of the scapula, inferior to infraspinatus. Subscapularis originates on the anterior surface of the scapula. All of these muscles insert on the upper humerus.

Flexion of the elbow is controlled principally by two muscles: biceps brachii, which originates on the scapula, and brachialis which originates on the humerus. These muscles are opposed by triceps brachii. This muscle originates on the scapula and humerus and inserts on the olecranon process of the ulna. The elbow is rotated by anconeus.

Many smaller muscles run from the radius and ulna to the wrist and hand. Four muscles which flex the wrist originate from the common flexor tendon which attaches to the medial epicondyle of the humerus. These muscles are pronator teres, palmaris longus, flexor carpi radialis and flexor carpi ulnaris. These muscles are opposed by extensor carpi radialis longus, extensor carpi radialis brevis and extensor carpi ulnaris.

Smaller muscles, such as extensor indicis, flexor digitorum superficialis and flexor pollicis longus provide fine control of the fingers.

English - Japanese Glossary

anconeus: 肘筋 (chuukin); biceps brachii: 上腕二頭筋 (jouwannitoukin); brachialis: 上腕筋 (jouwankin); brachioradialis: 腕橈骨筋 (wantoukotsukin); deltoid: 三角筋 (sankakukin); extensor carpi radialis brevis: 短橈側手根伸筋 (tantousokushukonshinkin); extensor carpi radialis longus: 長橈側手根伸筋 (choutousokushukonshinkin); extensor carpi ulnaris: 尺側手根伸筋 (shakusokushukonshinkin); extensor indicis: 示指伸筋 (jishishinkin); flexor carpi radialis: 橈側手根屈筋 (tousokushukonkukkin); flexor carpi ulnaris: 尺側手根屈筋 (shakusokushukonkukkin); flexor digitorum superficialis: 浅指屈筋 (senshikukkin); flexor pollicis longus: 長母指屈筋 (chouboshikukkin); infraspinatus: 棘下筋 (kyokukakin); latissimus dorsi: 広背筋 (kouhaikin); palmaris longus: 長掌筋 (choushoukin); pectoralis major: 大胸筋 (daikyoukin); pectoralis minor: 小胸筋 (shoukyoukin); serratus anterior: 前鋸筋 (zenkyokin); subscapularis: 肩甲下筋 (kenkoukakin); supraspinatus: 棘上筋 (kyokujoukin); teres major: 大円筋 (daienkin); teres minor: 小円筋 (shouenkin); trapezius: 僧帽筋 (souboukin); triceps brachii: 上腕三頭筋 (jouwansantoukin)