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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]
Familial opposable triphalangeal thumb duplication is a limb malformation syndrome and a type of pre-axial polydactyly, characterized by having duplicated opposable triphalangeal thumbs. This condition can be a symptom of other genetic disorders, such as Holt–Oram syndrome and Fanconi anemia .
Triphalangeal thumb (TPT) is a congenital malformation where the thumb has three phalanges instead of two. The extra phalangeal bone can vary in size from that of a small pebble to a size comparable to the phalanges in non-thumb digits. The true incidence of the condition is unknown, but is estimated at 1:25,000 live births. [1]
Brachydactyly type D, also known as short thumb, [3] [1] stub thumb, [5] [6] or clubbed thumb, [5] [6] is a genetic trait recognised by a thumb being relatively short and round with an accompanying wider nail bed. The distal phalanx of such thumbs is approximately two-thirds the length
Radius (2) (Lined up with thumb) Hand (54 bones in total; 27 in each hand) Carpals. Scaphoid bone (2) Lunate bone (2) Triquetral bone (2) Pisiform bone (2) Trapezium (2) Trapezoid bone (2) Capitate bone (2) Hamate bone (2) Metacarpals (10 bones in total; 5 on each side) Phalanges of the hand (28 bones in total, 14 on each hand)
For example, humans have a 2-3-3-3-3 formula for the hand, meaning that the thumb has two phalanges, whilst the other fingers each have three. In the distal phalanges of the hand the centres for the bodies appear at the distal extremities of the phalanges, instead of at the middle of the bodies, as in the other phalanges.
The thumb (connected to the trapezium) is located on one of the sides, parallel to the arm. The palm has five bones known as metacarpal bones, one to each of the five digits. Human hands contain fourteen digital bones, also called phalanges, or phalanx bones: two in the thumb (the thumb has no middle phalanx) and three in each of the four ...
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs.A few other vertebrates such as the koala (which has two opposable thumbs on each "hand" and fingerprints extremely similar to human fingerprints) are often described as having "hands" instead of paws on their front limbs.