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1 Anatomy of the Thumb

The thumb consists of 3 bones:

• distal phalanx (of the first digit)
• proximal phalanx (of the first digit)
• first metacarpal

Its movements are controlled by eight muscles:

• opponens pollicis
• abductor pollicis brevis
• flexor pollicis brevis
• adductor pollicis
• flexor pollicis longus
• abductor pollicis longus
• extensor pollicis brevis
• extensor pollicis longus

The first four of these muscles are in the hand and the first three of these form the thenar eminence. The other muscles come from the forearm. The extensor pollicis longus tendon and extensor pollicis brevis tendon form what is know as the anatomical snuff box (an indentation on the lateral aspect of the thumb at its base) where one can usually palpate the radial artery.

2 Grips

Typical interdigital grips include the tips of thumb and second finger ( forefinger/ index finger) holding a pill or other small item, or thumb and sides of second and third fingers holding a pen or pencil.

3 Evolution theory

The opposable or prehensile thumb is usually associated with the theorised evolution of homo habilis, the forerunner of homo sapiens (the human being of today according the the theory of evolution). This, however, is the suggested result of evolution from homo erectus (around 1 million years ago ) via a series of intermediate anthropoid stages, and is therefore a much more complicated link.

The most important factor leading to the habile hand (and its thumb) is the freeing of the hands from their walking requirements - still so crucial for apes today, which in its turn was one of the consequences of the gradual pithecanthropoid and anthropoid adoption of the erect bipedal walkingWalking is the main form of animal locomotion on land, distinguished from running and crawling. When executed in shallow water, it is usually described as wading . The word is derived from the Old English walcan (to roll). Walking is generally distinguish gait - and the simultaneous development of a larger anthropoid brainFor other articles about other subjects named brain see brain (disambiguation). In the anatomy of animals, the brain or encephalon is the supervisory center of the nervous system. Although the brain is usually cited as the supervisory center of vertebrate in the later stages.

4 Other animals with opposable thumbs or digits

Many animals, primates and others, also have some kind of opposable thumb or toe:

• PandaPanda is a member of the bear family: Giant Panda, the "classic" black and white panda. Red Panda. The Giant Panda in particular is a favorite animal in popular culture. Panda is the name of a car model manifactured by Fiat. Panda is a software company sp - Panda paws have five clawed fingers plus an extra bone that works like an opposable thumb. This "thumb" is not really a finger (like our thumb is), but an extra-long wrist bone that works like a thumb.
• KoalaThe Koala Phascolarctos cinereus sometimes also spelled Phascolarct u s cinereus is a thickset arboreal marsupial herbivore endemic to Australia, and the only representative of its family, Phascolarctidae . Koalas are unmistakable: they are broadly simila - opposable toe on each foot, plus two opposable digits on each hand
• OpossumThe word opossum (usually pronounced without the leading 'O', or with only a very slight schwa) refers either to the Virginia Opossum in particular, or more generally to any of the other marsupials of magnorder Ameridelphia. Opossums are the only marsupia - opposable thumb
• Cebids (New World primates of Central and South America) - some have opposable thumbs
• Bornean OrangutanPongo pygmaeus Pongo abelii The Orangutan (also spelt Orang Utan Orang-utan sometimes incorrectly orangutang is a great ape with long arms and reddish, sometimes brown, hair native to Malaysia and Indonesia. Orangutan is derived from the Malay Orang Hutan - opposable thumbs so that its forefeet are really like hands. The interdigital grip gives them the ability to pick fruit. They also have an opposable big toe.