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The thumb contrasts with each of the other four fingers by being the only one that: Is opposable to the other four fingers; Has two phalanges rather than three. However, recently there have been reports that the thumb, like other fingers, has three phalanges, but lacks a metacarpal bone. [3]
It involves a handshake-type grip, where the object being gripped rests firmly against the palm and all fingers. A strong crush grip is useful in bone-crushing handshakes, or for breaking objects with pressure. In a pinch grip, the fingers are on one side of an object, and the thumb is on the other. Typically, an object lifted in a pinch grip ...
The radial nerve innervates the finger extensors and the thumb abductor; that is, the muscles that extend at the wrist and metacarpophalangeal joints (knuckles) and abduct and extend the thumb. The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, the first and second lumbricals. The ulnar ...
Three phalanges are present on each finger and toe, with the exception of the thumb and big toe, which possess only two. The middle and far phalanges of the fourth and [citation needed] fifth toes are often fused together (symphalangism). [1] [2] The phalanges of the hand are commonly known as the finger bones. The phalanges of the foot differ ...
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 lack of palmaris longus muscle does result in decreased pinch strength in fourth and fifth fingers. The absence of palmaris longus muscle is more prevalent in females than males. [5] The palmaris longus muscle can be observed by touching the pads of the fourth finger and thumb and flexing the wrist. The tendon, if present, will be visible ...
(The flexor pollicis longus, which is inserted into the distal phalanx of the thumb, is not considered part of the thenar eminence.) Opponens pollicis lies deep to abductor pollicis brevis. As its name suggests it opposes the thumb, bringing it against the fingers. This is a very important movement, as most of human hand dexterity comes from ...
[3] [5] [6] It has 27 bones, not including the sesamoid bone, the number of which varies among people, [7] 14 of which are the phalanges (proximal, intermediate and distal) of the fingers and thumb. The metacarpal bones connect the fingers and the carpal bones of the wrist. Each human hand has five metacarpals [8] and eight carpal bones.