Deep Outcropping Pollicis Muslces

Abductor Pollicis longus proximal attachment

Proximal halves of ulna, radius, and interosseous membrane

Abductor pollicis longus distal attachment

Base of 1st metacarpal

All the deep outcropping pollicis muscles are innervated by

Posterior interosseous nerve  (continuation of deep branch of radial nerve)

Abductor pollicis longus action

Abducts thumb and extends it at carpometacarpal joint

Extensor pollicis longus proximal attachment

Middle third of ulna and interosseous membrane

Extensor pollicis longus distal attachment

Dorsal aspect of base of distal phalanx of thumb

Extensor pollicis longus action

Extends distal phalanx of thumb at interphalangeal joint; extends metacarpophalangeal and carpometacarpal joints

Extensor pollicis brevis proximal attachment

Distal third of radius and interosseous membrane

Extensor pollicis brevis distal attachment

Dorsal aspect of base of proximal phalanx of thumb

Extensor pollicis brevis action

Extends proximal phalanx of thumb at metacarpophalangeal joint; extends carpometacarpal joint