(human) finger

자료: Wikipedia, http://www.answers.com/finger

For other uses, see Finger (disambiguation).

Fingers of the human left hand

A finger is a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates.^[1][2] Normally humans have five digits, termed phalanges,^[2] on each hand (exceptions are polydactyly, hypodactyly and digit loss). The first digit is the thumb, followed by index finger, middle finger, ring finger, and little finger or pinky. Some other languages use the same generic term for all five digits of a hand.

English dictionaries describe finger as meaning either one of the five digits including the thumb, or one of the four excluding the thumb (in which case they are numbered from 1 to 4 starting with the index finger closest to the thumb).^[2][1][3] Linguistically, it appears that the original sense was to include the thumb as a finger: *penkwe-ros^{[citation needed]} (also rendered as*penqrós^{[citation needed]}) was, in the inferred Proto-Indo-European language, a suffixed form of *penkwe (or *penqe), "five", which has^{[citation needed]} given rise to many Indo-European-family words (tens of them defined in English dictionaries) that involve or flow from concepts of fiveness.

Chimpanzees have lower limbs that are specialized for manipulation, and (arguably) have fingers on their lower limbs as well. The term 'finger' is not applied to the digits of most other animals, such as canines, felines, or ungulates, none of which can engage in fine manipulation with their forelimbs as a primate can.

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Function

Further information: Hand#Muscles and tendons

Each finger may flex and extend, abduct and adduct, and so alsocircumduct. Flexion is by far the strongest movement. In humans, there are two large muscles that produce flexion of each finger, and additional muscles that augment the movement. Each finger may move independently of the others, though the muscle bulks that move each finger may be partly blended, and the tendons may be attached to each other by a net of fibrous tissue, preventing completely free movement. This is particularly noticeable when trying to extend the fourth digit (third finger) with the others flexed. 

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Fingers

Each of the fingers has unique cultural and functional significance. From the thumb on the radialside to the ulnar side of the hand, the fingers are in this order:

Thumb Index finger, also called 'pointer finger', or 'forefinger' Middle finger, the longest Ring finger, also known as fourth finger Little finger, also known as 'pinky'

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