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Supergames699 [2018-01-19 15:18:26 +0000 UTC]

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 remarkably similar to human fingerprints ) are often described as having "hands" instead of paws  on their front limbs. The raccoon  is usually described as having "hands" though opposable thumbs are lacking.[1]

Some evolutionary anatomists  use the term hand to refer to the appendage of digits on the forelimb more generally — for example, in the context of whether the three digits  of the bird  hand involved the same homologous  loss of two digits as in the dinosaur  hand.[2]

The human hand normally has five digits: four fingers  plus one thumb .[3] [4]  In some languages, the human hand is said to have five fingers, including the thumb as one of the fingers.[3]  It has 27 bones, not including the sesamoid bone , the number of which varies between people,[5]  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 [6]  and eight carpal bones.

Fingers contain some of the densest areas of nerve endings in the body, and are the richest source of tactile  feedback. They also have the greatest positioning capability of the body; thus, the sense of touch  is intimately associated with hands. Like other paired organs (eyes, feet, legs) each hand is dominantly controlled by the opposing brain hemisphere , so that handedness —the preferred hand choice for single-handed activities such as writing with a pencil, reflects individual brain functioning.

Among humans, the hands play an important function in body language  and sign language . Likewise the ten digits of two hands, and the twelve phalanges  of four fingers (touchable by the thumb) have given rise to number systems and calculation techniques.

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