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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 ...
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 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 ...
In anatomy, flexor is a muscle that contracts to perform flexion (from the Latin verb flectere, to bend), [1] a movement that decreases the angle between the bones converging at a joint. For example, one's elbow joint flexes when one brings their hand closer to the shoulder , thus decreasing the angle between the upper arm and the forearm .
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."
These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the proximal phalanges. [1] Being condyloid, they allow the movements of flexion, extension, abduction, adduction and circumduction (see anatomical terms of motion) at the joint. [1]
Likewise, flexion at the interphalangeal joint by flexor pollicis longus is considerably reduced in wrist flexion. [ 2 ] It also applies an extensor force at the metacarpophalangeal joint together with the extensor pollicis brevis and extends and adducts at the carpometacarpal joint of the thumb.
The muscle is inserted onto the radial sesamoid bone of the metacarpophalangeal joint. It acts to flex, adduct, and abduct the thumb, and is therefore also able to oppose the thumb. The superficial head is innervated by the median nerve, while the deep head is innervated by the ulnar nerve (C8-T1). [29]