Hand

"Hands" redirects here. For other uses, see Hand (disambiguation) and Hands (disambiguation).

Hand
Back of a human's left hand
Front of a human's left hand
Details
VeinDorsal venous network of hand
NerveUlnar, median, radial nerves
Identifiers
Latinmanus
MeSHD006225
TA98A01.1.00.025
TA2148
FMA9712
Anatomical terminology

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. 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 usually has five digits: four fingers plus one thumb;[3][4] these are often referred to collectively as five fingers, however, whereby the thumb is included as one of the fingers.[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.

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.

  1. ^ Thomas, Dorcas MacClintock; illustrated by J. Sharkey (2002). A natural history of raccoons. Caldwell, N.J.: Blackburn Press. p. 15. ISBN 978-1-930665-67-5.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. ^ Cite error: The named reference Xing was invoked but never defined (see the help page).
  3. ^ a b Latash, Mark L. (2008). Synergy. Oxford University Press, US. pp. 137–. ISBN 978-0-19-533316-9.
  4. ^ Kivell, Tracy L.; Lemelin, Pierre; Richmond, Brian G.; Schmitt, Daniel (2016). The Evolution of the Primate Hand: Anatomical, Developmental, Functional, and Paleontological Evidence. Springer. pp. 7–. ISBN 978-1-4939-3646-5.
  5. ^ Goldfinger, Eliot (1991). Human Anatomy for Artists : The Elements of Form: The Elements of Form. Oxford University Press. pp. 177, 295. ISBN 9780199763108.
  6. ^ O'Rahilly, Ronan; Müller, Fabiola (1983). Basic Human Anatomy: A Regional Study of Human Structure. Saunders. p. 93. ISBN 9780721669908.
  7. ^ Cite error: The named reference Schmidt 2003 105 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Marieb was invoked but never defined (see the help page).