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The muscles of the thumb are nine skeletal muscles located in the hand and forearm. The muscles allow for flexion, extension, adduction, abduction and opposition of the thumb. The muscles acting on the thumb can be divided into two groups: The extrinsic hand muscles, with their muscle bellies located in the forearm, and the intrinsic hand ...
Extensor pollicis longus extends the terminal phalanx of the thumb. While abductor pollicis brevis and adductor pollicis, both attached to the extensor pollicis longus tendon, can extend the thumb's interphalangeal joint to the neutral position, only extensor pollicis longus can achieve full hyperextension at the interphalangeal joint.
The radial nerve innervates the finger extensors and the thumb abductor; that is, the muscles that extend at the wrist and metacarpophalangeal joints (knuckles) and abduct and extend the thumb. The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, the first and second lumbricals. The ulnar ...
Abduction of the thumb is defined as the movement of the thumb anteriorly, a direction perpendicular to the palm. The abductor pollicis brevis does this by acting across both the carpometacarpal joint and the metacarpophalangeal joint. It also assists in opposition and extension of the thumb.
The EPB inserts into the base of the first phalanx of the thumb [2] to extend and abduct the thumb at the carpometacarpal and MCP joints. [5] The EPL inserts on the base of the distal phalanx of the thumb. It uses the dorsal tubercle on the radius as fulcrum [2] to help the EPB with its action as well as extending the distal phalanx of the ...
An accessory abductor pollicis longus (AAPL) tendon is present in more than 80% of people, and a separate muscle belly is present in 20% of people. In one study, the accessory tendon was inserted into the trapezium (41%); proximally on the abductor pollicis brevis (22%) and opponens pollicis brevis (5%); had a double insertion on the trapezium and thenar muscles (15%); or the base of the first ...
Thumb abduction and extension at metacarpophalangeal joint. Forms radial (thumb side) border of the anatomical snuff box. De Quervain's tenosynovitis: 2 Extensor carpi radialis longus tendon. Extensor carpi radialis brevis tendon. Extension of wrist Intersection syndrome: 3 Extensor pollicis longus tendon
The extensor pollicis brevis arises from the ulna distal to the abductor pollicis longus, from the interosseous membrane, and from the dorsal surface of the radius. [1]Its direction is similar to that of the abductor pollicis longus, its tendon passing the same groove on the lateral side of the lower end of the radius, to be inserted into the base of the first phalanx of the thumb.