Muscles of the Thumb & Hand

Abductor Digiti Minimi

Action: Abduct the fifth finger, Assist in opposition of the fifth finger toward the thumb Origin: Pisiform and tendon of flexor carpi ulnaris Insertion: Base of proximal phalanx of fifth finger, ulnar surface Nerve innervation: Ulnar C(7), 8, T1

Dorsal Interossei

Action: Abduct the second, third, and fourth fingers at the metacarpophalangeal joints, Assist to flex the second, third, and fourth fingers at the metacarpophalangeal joints, Assist to extend the second, third, and fourth fingers at the interphalangeal joints Origin: Adjacent sides of all metacarpals Insertion: Base of the proximal phalanx of the second, third, and fourth fingers and the extensor aponeurosis Nerve innervation: Ulnar C8, T1

Abductor Pollicis Brevis

Action: Abduct the thumb, Assist in opposition of the thumb Origin: Flexor retinaculum, trapezium and scaphoid tubercles Insertion: Base of proximal phalanx of thumb Nerve innervation: Median C6, 7, 8, T1

Abductor Pollicis Longus

Action: Abduct the thumb, Extend the thumb, & Abduct the wrist Origin: Posterior surface of radius and ulna, and interosseous membrane Insertion: Base of first metacarpal Nerve innervation: Radial C6, 7, 8

Adductor Pollicis

Action: Adduct the thumb, Assist to flex the thumb Origin: Capitate, second and third metacarpals Insertion: Base of proximal phalanx of thumb Nerve innervation: Ulnar C8, T1

Palmar Interossei

Action: Adduct the thumb, second, fourth, and fifth fingers toward the third finger, Assist to flex the thumb, second, fourth, and fifth fingers at the metacarpophalangeal joints, Assist to extend the thumb, second, fourth, and fifth fingers at the interphalangeal joints Origin: Base of first, second, fourth, and fifth metacarpals Insertion: Base of the proximal phalanx of the related finger and the extensor aponeurosis Nerve innervation: Ulnar C8, T1

Lumbricals of the hand

Action: Extend the second through fifth fingers at the interphalangeal joints, flex the second through fifth fingers at the metacarpophalangeal joints Origin: Surfaces of the flexor digitorum profundus tendons Insertion: Extensor aponeurosis on dorsal surface of phalanges Nerve innervation: Second and Third fingers - Median C(6), 7, 8, T1 Fourth and Fifth fingers - Ulnar C(7), 8, T1

Extensor Pollicis Longus

Action: Extend the thumb & Abduct the wrist Origin: Posterior surface of ulna and interosseous membrane Insertion: Base of distal phalanx of thumb Nerve innervation: Radial C6, 7, 8

Extensor Pollicis Brevis

Action: Extend the thumb, Abduct the wrist Origin: Posterior surface of radius and interosseous membrane Insertion: Base of proximal phalanx of thumb Nerve innervation: Radial C6, 7, 8

Flexor Digiti Minimi Brevis

Action: Flex the fifth finger, Assist in the opposition of the fifth finger toward the thumb Origin: Hook of hamate and flexor retinaculum Insertion: Base of proximal phalanx of fifth finger, palmar surface Nerve innervation: Ulnar C(7), 8, T1

Flexor Pollicis Brevis

Action: Flex the thumb, Assist in opposition of the thumb Origin: Superficial Head - Flexor retinaculum Deep Head - Trapezium, trapezoid and capitate Insertion: Base of proximal phalanx of thumb Nerve innervation: Superficial Head - Median C6, 7, 8, T1 Deep Head - Ulnar C8, T1

Flexor Pollicis Longus

Action: Flex the thumb, Assist to flex the wrist Origin: Anterior surface of radius and interosseous membrane Insertion: Base of distal phalanx of thumb Nerve innervation: Median C(6), 7, 8, T1

Opponens Digiti Minimi

Action: Opposition of the fifth finger at the carpometacarpal joint Origin: Hook of hamate and flexor retinaculum Insertion: shaft of fifth metacarpal, ulnar surface Nerve innervation: Ulnar C(7), 8, T1

Opponens Pollicis

Action: Opposition of the thumb at the carpometacarpal joint (bringing in the pads of the thumb and fifth finger together) Origin: Flexor retinaculum and tubercle of the trapezium Insertion: Entire length of first metacarpal bone, radial surface Nerve innervation: Median C6, 7, 8, T1