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The muscles of the hand can be subdivided into two groups: the extrinsic and intrinsic muscle groups. 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 ...
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 ...
The second, third, and fourth dorsal interossei have insertions both proximally on the base of the metacarpal and hood, and distally on the lateral bands and central tendon of the extensor mechanism. The abductor digiti minimi, effectively the "fifth dorsal interosseus" or the dorsal interosseus of the little finger, has only a proximal insertion.
The extensor carpi radialis longus (ECRL) has the most proximal origin of the extrinsic hand extensors. It originates just distal to the brachioradialis at the lateral supracondylar ridge of the humerus, the lateral intermuscular septum, and by a few fibers at the lateral epicondyle of the humerus. [1]
The lumbricals are four, small, worm-like muscles on each hand. These muscles are unusual in that they do not attach to bone. Instead, they attach proximally to the tendons of flexor digitorum profundus, [1] [2] [3] and distally to the extensor expansions.
The abductor digiti minimi is the most variable hypothenar muscle, [4] and might be joined by accessory slips from the tendon of the flexor carpi ulnaris, the flexor retinaculum, the fascia of the distal forearm, or the tendon of the palmaris longus. Occasionally, the muscle is partially inserted onto the fifth metacarpal bone. [5]
Interosseous muscles of the hand; Details; Origin: Dorsal: metacarpal bones 1 to 5. Palmar: metacarpal bones of digits 2, 4, 5: Insertion: Dorsal: bases of proximal phalanges and extensor expansions of digits 2 to 4. Palmar: base of proximal phalanx and extensor expansion of the same digit from which it originated. Nerve: deep branch of the ...
In African apes, adductor pollicis is notably well-developed, with an origin on the carpus and its ligaments, and an insertion that has migrated distally, in some cases as far as the distal phalanx. The insertion of the PPIM into the extensor mechanism is likely to have evolved with tool usage in early hominids. [3]