Information AboutThumb |
| CATEGORIES ABOUT THUMB | |
| fingers | |
The thumb is one of the five Finger s. ANATOMY OF THE THUMB Bones The thumb consists of 3 bones:
Muscles Its movements are controlled by eight muscles (each with "pollicis" in the name): The extensor pollicis longus tendon and extensor pollicis brevis tendon form what is known 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 . In the hand, the abductor pollicis brevis, adductor pollicis, flexor pollicis brevis, and opponens pollicis form the Thenar Eminence . Hitchhiker's thumb The thumb when extended (as in a " Thumbs-up ") can also appear to bend backwards toward the nail and outwards, a Recessive Congenital Condition known as "hitchhiker's thumb", whereas for other people it will extend straight out with little backward bending. Having either condition appears to have no effect on the thumb's function. AS ONE OF FIVE FINGERS, AND AS COMPANION TO FOUR FINGERS The English word "finger" has two senses, even in the context of appendages of a single typical human hand: # Any of the five digits. # The four digits, not including the thumb. Linguistically, it appears that the original sense was the broader of these two: ''penkwe-ros'' (also rendered as ''penqrós'') was, in the inferred Proto-Indo-European language, a suffixed form of ''penkwe'' (or ''penqe''), which has given rise to many Indo-European -family words (tens of them defined in English dictionaries) that involve or flow from concepts of fiveness. The thumb shares the following with each of the (other) four fingers:
The thumb contrasts with each of the (other) four by being the only finger that:
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. ORIGIN OF THE THUMB The evolution of the opposable or '' (around 1 Mya ) via a series of intermediate Anthropoid stages, and is therefore a much more complicated link. The most important factors leading to the habile hand (and its thumb) are:
IMPORTANCE OF THE OPPOSABLE THUMB The thumb, unlike other fingers, is opposable, in that it is the only digit on the human hand which is able to oppose or turn back against the other four fingers, and thus enables the hand to refine its grip to hold objects which it would be unable to do otherwise. The opposable thumb has helped the human species develop more accurate ''. 2007, accessed April 26, 2007. In addition, the opposable thumb has given rise to a popular gesture referred to as the "Thumbs-Up", a symbol of approval in western culture. OTHER ANIMALS WITH THUMBS Many animals, primates and others, also have some kind of opposable thumb or toe:
SEE ALSO
REFERENCES |
|
|