Wrist/Hand Extensors & Forearm Supinators

O: posterior surface of the radius, interosseous membrane, posterolateral ulna I: radial side of the base of the first metacarpal A: abducts the thumb at CMC joint In: radial nerve

abductor pollicis longus (second layer)

O: common extensor tendon & the middle one-half of the posterior border of the ulna I: medial side of the base of the 5th metacarpal A: extends the wrist; adducts the hand In: radial nerve

extensor capri ulnaris (first layer)

O: common extensor tendon I: base of the third metacarpal bone A: extends the wrist; abducts the hand In: radial nerve

extensor carpi radialis brevis (first layer)

O: lateral supracondylar ridge of the humerus I: base of the second metacarpal bone A: extends the wrist and abducts the hand In: radial nerve

extensor carpi radialis longus (first layer)

O: common extensor tendon I: joins the extensor digitorum tendon to the 5th digit and inserts into the extensor expansion/hood A: extends the MCP, PIP and DIP joints of the 5th digit In: radial nerve

extensor digiti minimi (first layer)

O: common extensor tendon I: through the "extensor expansion/hood" inserts on posterior middle of middle phalanx; and lateral sides of the distal phalanx of digits 2-5 A: extends the MCP, PIP, and DIP joints of digits 2-5; extends wrist In: radial nerve

extensor digitorum (first layer)

O: interosseous membrane and the posterior surface of the distal ulna I: its tendon joins the tendon of the extensor digitorum to the second digit A: extends the index finger at the MCP, PIP, and DIP joints In: radial nerve

extensor indicis (second layer) *index finger*

O: interosseous membrane and the posterior surface of the distal radius I: base of the proximal phalanx of the thumb A: extends the thumb at the MCP joint N: radial nerve

extensor pollicis brevis (second layer)

O: interosseous membrane and posterior surface of the ulna I: base of the distal phalanx of the thumb A: extends the thumb at the IP joint In: radial nerve

extensor pollicis longus (second layer)

O: lateral epicondyle of the humerus & annular ligament; supinator crest and fossa I: lateral side of proximal one-third of the radius A: supinates the forearm In: radial nerve

supinator (second layer)