Muscles of the Forearm and Hand

Hints for actions

“radialis” = abduct the wrist

“ulnaris” = adduct the wrist

Anterior Forearm

• pronators of the forearm and flexors of the wrist and digits

• 8 Muscles (4 superficial, 1 intermediate, 3 deep)

• ALL innervated by MEDIAN N. EXCEPT 1 ½ mucles which are innervated by the ULNAR N.

Superficial Anterior Forearm Muscles

• ALL originate on or near medial epicondyle of the humerus

• Pronator Teres m

• Flexor Carpi radialis m

• Palmaris longus m

• Flexor carpi ulnaris m.

• Flexor digitorum superficialis m.

Pronator Teres m (A, Inn)

A: pronates the forearm and flexes the elbow

Inn: Median n.

Flexor Carpi radialis m (A and Inn)

A: Flexes and abducts wrist

Inn: Median n.

Palmaris Longus m (A and inn)

A: Flexes wrist

Inn: Median n.

Flexor carpi ulnaris m (A and Inn)

A: Flex and adduct wrist

Inn: Ulnar n.

Flexor digitorum superficialis m (A and Inn)

A: flexes digits 2-5 and flexes wrist

inn: Median n

Deep Anterior Forearm Muscles

• ALL originate on interosseous membrane of radius/ulna

• flexor digitorum profundus m

• flexor pollicis longus

• Pronator quadratus m

Flexor digitorum profundus m (A and inn)

A: flexes digits 2-5 and wrist

inn: median n (digits 2 + 3) and ulnar n (digits 4 + 5)

Flexor pollicis longus m (A and inn)

A: flexes pollex and wrist

Inn: Median n

Pronator quadratus m (a and inn)

A: pronates forearm

Inn: Median n

Posterior Forearm

• supernators and extensors

• ALL INNERVATED BY RADIAL NERVE

Superficial posterior forearm

• All 7 originate on or near the lateral epicondyle of the humerus

• Brachioradialis m

• extensor carpi radialis longus m

• extensor carpi radialis brevis m

• extensor digitorum m.

• extensor digiti minimi m

• extensor carpi ulnaris m

• anconeus m

Brachioradialis m (A and Inn)

A: flexes elbow (drinking muscle)

Inn: radial n

Extensor carpi radialis longus and brevis m (A and Inn)

A: extends wrist and abducts wrist

Inn: radial n

Extensor digitorum m (a and inn)

A: extend digits 2-5 and wrist

inn: radial n

Extensor digiti minimi m (a and inn)

A: extend digit 5 and wrist

inn: radial n.

Extensor carpi ulnaris m (a and inn)

A: extend and adduct wrist

inn: radial n

Anconeus m (a and Inn)

A: extend elbow “triceps little helper”

Inn: radial n.

Deep posterior forearm muscles

• ALL 5 originate on interosseous membrane of radius/ulna

• supinator m

• abductor pollicis longus m

• extensor pollicis brevis m

• extensor pollicis longus m

• extensor indicis m

Supinator m (A and Inn)

A: supinates forearm

inn: radial n.

Abductor pollicis longus m ( A and inn)

A: Abducts pollex

Inn: Radial n

extensor pollicis brevis and longus (a and inn)

A: extend pollex

Inn: radial n

Extensor indicis m (a and inn)

A: extends digit 2

Inn: radial n.

Muscles of the hand

• 20 hand muscles

• 5 are innervated by MEDIAN N while the rest are innervated by ULNAR N.

• thenar eminence (3)

• hypothenar eminence (3)

• lumbricals (4)

• adductor pollicis m

• palmar and dorsal interosseous mm (8)

• palmaris brevis m

Thenar vs Hypothenar

• Thenar is by the thumb while the hypothenar is by the pinky

• each contain three muscles (a flexor, abductor, and opponens)

Abductor digiti minimi m (a and Inn)

A: abduct digit 5

Inn: ulnar n

*abductor muscles will be closer to the outside

Flexor digiti minimi brevis m (a and inn)

A: flex digit 5

Inn: ulnar n

opponens digiti minimi m (a and inn)

A: opposes digit 5

Inn: ulnar n

Abductor pollicis brevis m (a and inn)

A: abducts pollex

Inn: median n

Flexor pollicis brevis m (a and inn)

A: flexes pollex

inn: median n

Opponens pollicis m (a and inn)

A: opposes pollex

inn: median n

Lumbrical Muscles (A and Inn)

A: Flex at the metacarpal phalangial joint and extend at the interphalangial joint (table top action)

Inn: lumbricals 1 + 2 innervated by median n; lumbricals 3 + 4 innervated by ulnar

Adductor Pollicis m (a and inn)

A: adduct pollex

Inn: ulnar n

Palmar interosseous mm (A and inn)

A: Adduction of the digits (PAD)

Inn: Ulnar n

Dorsal interosseous mm (A and Inn)

A: Abduction of the digits (DAB)

Inn: Ulnar n.