Muscles of the Forearm and Hand

Forearm and hand
Muscle	Origin	Insertion	Action	Notes
Extensor digitorum	Common extensor tendon from lateral epicondyle of humerus	Dorsal surface of middle and distal phalanges 2-5 ( four fingers)	Extends four fingers, assists in extension of the wrist
Pronator quadratus
Palmaris longus	Medial epicondyle of humerus	Palmar aponeurosis	Flexion of hand and wrist	Flex wrist against resistance to find tendon. May be absent in one or both sides in some people.
Flexor digitorum superficialis	Medial epicondyle of humerus, coronoid process of ulna, proximal radius	Four tendons into the middle phalanges of fingers 2-5, palmar surface	Flexes the middle and proximal phalanges of fingers 2-5, flexion of the wrist and forearm.	Median nerve and ulnar artery are under origin
Flexor carpi radialis	Medial epicondyle of humerus	Base of 2^nd to base of 3^rd metacarpal bone	Flexes and abducts the wrist, pronation of the forearm and flexion of the elbow
Flexor carpi ulnaris	Medial epicondyle of humerus, medial olecranon and proximal posterior ulna	Pisiform bone	Flexes and adducts the wrist and flexes the elbow
Extensor carpi radialis longus	Lateral supracondylar ridge of humerus	Base of 2^nd metacarpal bone dorsal side	Extends and abducts the wrist, flexes the elbow
Extensor carpi radialis brevis	Lateral epicondyle of humerus	Dorsal surface of base of 3^rd metacarpal bone	Extends and assists in abduction of the wrist
Extensor carpi ulnaris	Lateral epicondyle of humerus, posterior border of ulna	Base of 5^th metacarpal bone, ulnar side	Extends and adducts the wrist	Tendon runs through a groove between the head of the ulna and the styloid process of ulna
Flexor digitorum profundus	Anterior and medial surfaces of proximal ¾ of ulna	Four tendons into bases of distal phalanges on anterior surface	Flexes distal interphalangeal joints of four fingers, flexes proximal interphalageal and metacarpopphalangeal joints
Flexor pollicus longus	Anterior surface of radius, deep to flexors	Distal phalange of thumb	Flexes thumb
Supinator	Lateral epicondyle of humerus, posterior ulna	Proximal anterior shaft of humerus	Supinates forearm
Extensor pollicus longus and brevis	Posterior surface of radius and ulna, deep to extensors	Brevis –proximal phalange of thumb Longus- distal phalange of thumb	Extends the thumb
Opponens pollicis	Palmar retinaculum, trapezium	1^st metacarpal anterior surface	Opposition of thumb to each digit. Rotates 1^st metacarpal so the thumbnail faces the ceiling when the hand is resting palm up.

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