Muscles of the Arm and Forearm: Origin, Insertion, and Action
Triceps brachii
Origin: Long head: inferior margin of glenoid fossa of scapula; Lateral head: posterior surface of humerus; Medial head: posterior surface of humerus, inferior to origin of lateral head. Insertion: olecranon process of ulna. Action: extension of forearm; long head extends and adducts arm.
Biceps brachii
Origin: Long head: superior margin of glenoid fossa of scapula; short head: coracoid process of scapula. Insertion: radial tuberosity of radius; fascia of medial forearm via bicipital aponeurosis. Action: flexion and supination of forearm; flexion of arm.
Pronator quadratus
Origin: anterior surface of distal ulna. Insertion: anterior surface of distal radius. Action: pronation of the forearm.
Brachialis
Origin: anterior surface of humerus. Insertion: coronoid process of ulna. Action: flexion of forearm.
Flexor pollicis longus
Origin: anterior surface of radius; interosseous membrane. Insertion: distal phalanx of thumb. Action: flexion of the wrist and thumb.
Coracobrachialis
Origin: coracoid process of scapula. Insertion: medial surface of humerus. Action: flexion and adduction of arm.
Extensor digitorum
Origin: lateral epicondyle of humerus. Insertion: extensor expansions of medial four digits. Action: extension of wrist and fingers.
Extensor digiti minimi
Origin: lateral epicondyle of humerus. Insertion: extensor expansions of the fifth digit. Action: extension of the fifth digit.
Extensor carpi radialis brevis
Origin: lateral epicondyle of humerus. Insertion: metacarpal of the third digit. Action: extension and abduction of the wrist.
Anconeus
Origin: lateral epicondyle of humerus. Insertion: olecranon process of ulna. Action: very weak extension of the forearm.
Extensor carpi ulnaris
Origin: lateral epicondyle of humerus; posterior surface of ulna. Insertion: metacarpal of the fifth digit. Action: extension and adduction of the wrist.
Supinator
Origin: lateral epicondyle of humerus; proximal ulna. Insertion: posterior, lateral, and anterior surfaces of proximal radius. Action: supination of the forearm.
Brachioradialis
Origin: lateral supracondylar ridge of humerus. Insertion: lateral surface of distal radius. Action: flexion of the forearm.
Extensor carpi radialis longus
Origin: lateral supracondylar ridge of humerus. Insertion: metacarpal of the second digit. Action: extension and abduction of the wrist.
Flexor digitorum profundus
Origin: medial and anterior surfaces of ulna; interosseous membrane. Insertion: distal phalanges of medial four digits. Action: flexion of wrist and fingers.
Flexor carpi radialis
Origin: medial epicondyle of humerus. Insertion: base of metacarpal of the second digit. Action: flexion and abduction of the wrist.
Palmaris longus
Origin: medial epicondyle of humerus. Insertion: flexor retinaculum; palmar aponeurosis. Action: flexion of the wrist.
Pronator teres
Origin: medial epicondyle of humerus; coronoid process of ulna. Insertion: lateral surface of radius. Action: pronation and flexion of the forearm.
Flexor digitorum superficialis
Origin: medial epicondyle of humerus; coronoid process of ulna; anterior surface of radius. Insertion: middle phalanges of medial four digits. Action: flexion of wrist and fingers.
Flexor carpi ulnaris
Origin: medial epicondyle of humerus; olecranon process of ulna. Insertion: medial carpal bones; metacarpal of fifth digit. Action: flexion and adduction of the wrist.
Extensor pollicis brevis
Origin: posterior surface of radius and interosseous membrane. Insertion: proximal phalanx of thumb. Action: extends thumb.
Extensor pollicis longus
Origin: posterior surface of ulna and interosseous membrane. Insertion: distal phalanx of thumb. Action: extends thumb.
Extensor indicis
Origin: posterior surface of ulna and interosseous membrane. Insertion: extensor expansion of second digit. Action: extends the second digit.
Abductor pollicis longus
Origin: posterior surfaces of radius and ulna; interosseous membrane. Insertion: metacarpal of thumb. Action: abducts and extends thumb.
