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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 superficial head arises on the flexor retinaculum, while the deep head originates on three carpal bones: the trapezium, trapezoid, and capitate. 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 thenar eminence is the mound formed at the base of the thumb on the palm of the hand by the intrinsic group of muscles of the thumb. [1] The skin overlying this region is the area stimulated when trying to elicit a palmomental reflex. The word thenar comes from Ancient Greek θέναρ (thenar) 'palm of the hand'. [2]
The lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints, [1] and extend the interphalangeal joints. [1] [2] The lumbrical muscles of the foot also have a similar action, though they are of less clinical concern.
Arteries of the right hand (palmar view) The hand is supplied with blood from two arteries, the ulnar artery and the radial artery. These arteries form three arches over the dorsal and palmar aspects of the hand, the dorsal carpal arch (across the back of the hand), the deep palmar arch, and the superficial palmar arch.
The primary role of the hand itself is grasping and manipulation; tasks for which the hand has been adapted to two main grips — power grip and precision grip. In a power grip an object is held against the palm and in a precision grip an object is held with the fingers, both grips are performed by intrinsic and extrinsic hand muscles together.
The palmar interosseous muscles adduct the fingers towards the middle finger. This is in contrast to the dorsal interossei , which abduct the fingers away from the middle finger. In addition (like dorsal interossei ) they flex the finger at the metacarpo-phalangeal joint and extend the finger at the interphalangeal joint and thus assist the ...