Finger
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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.
Normally humans have five digits on each hand (exceptions are polydactyly, hypodactyly and digit loss). The first digit is the thumb. Some English speakers may consider the thumb to be a type of finger, leading to the conclusion that humans have five fingers on each hand. Others may consider the term 'finger' to apply only to those four digits that are medial to the thumb, leading to the conclusion that humans have four fingers on each hand.[citation needed] Some other languages, such as Russian, use the same generic term for all five digits of a hand (Moreover, all 20 digits of a human are referred to with the same term in Russian, a possible translatability problem).
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 a plantigrade animal such as a dog, which cannot engage in fine manipulation with its forelimbs as a human can.
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[edit] Function
Each finger may flex and extend, abduct and adduct; therefore it may also circumduct. 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.
Fingers are usually moved under conscious control. In humans, they are used for grasping, typing, grooming and writing, and many other activities. They are also used in signaling, as when wearing a wedding ring, finger counting or when communicating in sign language.
Fingers do not contain muscles other than arrector pili muscles. The muscles that move the finger joints are in the palm and forearm. The long tendons that deliver motion from the forearm muscles may be observed to move underneath the skin at the wrist and on the back of the hand.
[edit] Fingers
Each of the fingers has unique cultural and functional significance. From the thumb on the radial side 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
- little finger, also known as 'pinky'
[edit] Disease
A rare anatomical variation affects 1 in 500 humans, in which the individual has more than the usual number of digits; this is known as polydactyly. A human may also be born without one or more fingers, leading to a reduced total number.
Phalanges are commonly fractured. A damaged tendon can cause significant loss of function in fine motor control, such as with a mallet finger.
The fingers are commonly affected by diseases such as rheumatoid arthritis and gout. Diabetics often use the fingers to obtain blood samples for regular blood sugar testing. Raynaud's phenomenon is a neurovascular disorder that affects the fingers.
[edit] See also
- Digit ratio (relative finger lengths)
- Home row (of keyboards)
- List of polydactyl people
- Toe
HEAD: Skull - Forehead – Eye – Ear – Nose – Mouth – Tongue – Teeth – Jaw – Face – Cheek – Chin
NECK: Throat – Adam's apple - Larynx
TORSO: Shoulders – Spine – Chest – Breast – Ribcage – Abdomen – Belly button
LIMBS: Arm – Elbow – Forearm – Wrist – Hand – Finger (Thumb/Index/Middle/Ring/Little) – Leg – Lap – Thigh – Knee – Calf – Heel – Ankle – Foot – Toe (Hallux)
