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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 ...
Abductor pollicis brevis abducts the thumb. This muscle is the most superficial of the thenar group. Flexor pollicis brevis, which lies next to the abductor, will flex the thumb, curling it up in the palm. (The flexor pollicis longus, which is inserted into the distal phalanx of the thumb, is not considered part of the thenar eminence.)
The abductor pollicis brevis is a flat, thin muscle located just under the skin. It is a thenar muscle , and therefore contributes to the bulk of the palm's thenar eminence . It originates from the flexor retinaculum of the hand , the tubercle of the scaphoid bone, and additionally sometimes from the tubercle of the trapezium .
The human thumb also has other muscles in the thenar group (opponens and abductor brevis muscle), moving the thumb in opposition, making grasping possible. The extensors are located on the back of the forearm and are connected in a more complex way than the flexors to the dorsum of the fingers. The tendons unite with the interosseous and ...
The muscle's superficial head arises from the distal edge of the flexor retinaculum and the tubercle of the trapezium, the most lateral bone in the distal row of carpal bones. [1] It passes along the radial side of the tendon of the flexor pollicis longus. The deeper (and medial) head "varies in size and may be absent."
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 ...
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The flexor pollicis longus (/ ˈ f l ɛ k s ər ˈ p ɒ l ɪ s ɪ s ˈ l ɒ ŋ ɡ ə s /; FPL, Latin flexor, bender; pollicis, of the thumb; longus, long) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is unique to humans, being either rudimentary or absent in ...