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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 ...
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.)
Fractures of scaphoid can occur either with direct axial compression or with hyperextension of the wrist, such as a fall on the palm on an outstretched hand. Using the Herbert classification system, there are three main types of scaphoid fractures. 10%-20% of fractures are at the proximal pole, 60%-80% are at the waist (middle), and the ...
The extrinsic muscle groups are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm. The intrinsic group are the smaller muscles located within the hand itself. The muscles of the hand are innervated by the radial, median, and ulnar nerves from the brachial plexus. [1]
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 ...
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.
In non-human primates, there is only one flexor muscle for all the fingers, whereas in humans, the flexor pollicis longus becomes distinct. [7] Linburg–Comstock syndrome may be viewed as an evolutionary persistent structure. It is still inconclusive whether or not the connection is congenital or acquired at a later time point in life. [8]
This type of compression along the metacarpal bone is often sustained when a person punches a hard object, such as the skull or tibia of an opponent, or a wall. It can also occur as a result of a fall onto the thumb. This is a common injury sustained from bike falls, as the thumb is generally extended while around the handle bars.