Thumb
The 'thumbs up' gesture is a sign of approval in many cultures, and an obscene gesture in many others. For the Chinese newspaper see Thumbs Up (newspaper. For the Indian Cola drink see Thums Up A thumbs up or thumbs down is A gesture is a form of Non-verbal communication made with a part of the body used instead of or in combination with verbal communication.
Latin	pollex, digitus primus, digitus I
Artery	princeps pollicis artery
Lymph	infraclavicular lymph nodes[1]
MeSH	Thumb
Dorlands/Elsevier	p_27/12655361

Fingers

Thumb  • Index  • Middle  • Ring  • Little

The thumb is the lateral-most digit of the hand. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Arteries are Blood vessels that carry blood away from the Heart. The princeps pollicis ( principal artery of the thumb) arises from the Radial artery just as it turns medially towards the deep part of the hand it descends between The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. One or two deltopectoral lymph nodes (or infraclavicular nodes) are found beside the Cephalic vein, between the Pectoralis major and Deltoideus Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group The second Digit of a human Hand is also referred to as the index finger, pointer finger, forefinger, trigger finger, digitus The middle finger (or the long finger) is the third digit of the human Hand and usually the longest Finger, located between the Index finger The ring finger is the fourth digit of the human Hand, and the second most Ulnar Finger, located between the Middle finger and the The little finger, often called the pinky in American English and pinkie in Scottish English (from the Dutch word pink Human anatomical terms make up a distinct nomenclature to describe areas of the body to provide orientation when describing parts of Human anatomy, and to 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 The English adjective for thumb is pollical.

Contents 1 Anatomy of the opposable thumb 1.1 Bones 1.2 Muscles 1.3 Hitchhiker's thumb 2 As one of five digits, and as companion to four fingers 3 Grips 4 Origin of the thumb 5 Importance of the opposable thumb 6 Other animals with thumbs 7 See also 8 References

Anatomy of the opposable thumb

Bones

The thumb consists of three bones:

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

Muscles

Its movements are controlled by eight muscles (each with "pollicis" in the name):

Name	Location	Nerve
extensor pollicis longus	forearm	posterior interosseous nerve
abductor pollicis longus	forearm	posterior interosseous nerve
flexor pollicis longus	forearm	anterior interosseous nerve
extensor pollicis brevis	forearm	posterior interosseous nerve
abductor pollicis brevis	hand	median nerve
flexor pollicis brevis	hand	median nerve
opponens pollicis	hand	median nerve
adductor pollicis	hand	ulnar nerve (deep branch)

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) The radial artery can be palpated anteriorly at the wrist(not in the snuffbox) In the hand, the abductor pollicis brevis, adductor pollicis, flexor pollicis brevis, and opponens pollicis form the thenar eminence. In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species The name Phalanx (plural phalanges) is commonly given to the Bones that form Fingers and Toes In Primates such as Humans In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species The metacarpus is the intermediate part of the Hand Skeleton that is located between the Phalanges (bones of the fingers Distally and the The Extensor pollicis longus is much larger than the Extensor pollicis brevis muscle the origin of which it partly covers The posterior interosseous nerve (or dorsal interosseous nerve) is a Nerve in the foream The Abductor pollicis longus lies immediately below the Supinator and is sometimes united with it The posterior interosseous nerve (or dorsal interosseous nerve) is a Nerve in the foream The flexor pollicis longus is a muscle in the Forearm and Hand that flexes the thumb The anterior interosseous nerve ( volar interosseous nerve) is a branch of the Median nerve that supplies the deep muscles on the front of the Forearm, except The Extensor pollicis brevis lies on the medial side of and is closely connected with the Abductor pollicis longus. The posterior interosseous nerve (or dorsal interosseous nerve) is a Nerve in the foream The abductor pollicis brevis is a muscle in the hand that functions as an abductor of the Thumb. The median nerve is a Nerve that runs down the Arm and Forearm. The flexor pollicis brevis is a muscle in the hand that flexes the thumb The median nerve is a Nerve that runs down the Arm and Forearm. The opponens pollicis is a small triangular muscle in the hand which functions to oppose the thumb The median nerve is a Nerve that runs down the Arm and Forearm. The adductor pollicis muscle is a Muscle in the Hand that functions to adduct the thumb In Human anatomy, the ulnar nerve is a nerve which runs near the Ulna bone The anatomical snuffbox, or radial fossa, (in Latin Foveola radialis) is a triangular deepening on the radial, dorsal aspect of the hand - at The thenar eminence is the body of Muscle on the palm of the human Hand just beneath the Thumb.

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. For the Chinese newspaper see Thumbs Up (newspaper. For the Indian Cola drink see Thums Up A thumbs up or thumbs down is Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent Having either condition appears to have no effect on the thumb's function.

As one of five digits, 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:

1. The four digits, not including the thumb.
2. Any of the five digits.

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:

• Having a skeleton of phalanges, joined by hinge-like joints that provide flexion toward the palm of the hand
• Having a "back" surface that features hair and a nail, and a hairless palm-of-the-hand side with fingerprint ridges instead

The thumb contrasts with each of the (other) four by being the only finger that:

• Is opposable
• Has two phalanges rather than three
• Has its inmost phalanx so close to the wrist
• Has much greater breadth and stubby proportions
• Is attached to such a mobile metacarpus (which produces most of the opposability)

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. The name Phalanx (plural phalanges) is commonly given to the Bones that form Fingers and Toes In Primates such as Humans A fingerprint is an impression of the friction ridges of all or any part of the finger The metacarpus is the intermediate part of the Hand Skeleton that is located between the Phalanges (bones of the fingers Distally and the The second Digit of a human Hand is also referred to as the index finger, pointer finger, forefinger, trigger finger, digitus The second Digit of a human Hand is also referred to as the index finger, pointer finger, forefinger, trigger finger, digitus

Origin of the thumb

The evolution of the opposable or prehensile thumb is usually associated with Homo habilis, the forerunner of Homo sapiens. Prehensility or Prehensile is the quality of an Appendage or organ that has adapted for grasping or holding Homo habilis (ˈhoʊmoʊ ˈhæbəlɪs ("handy man" "skillful person" is a Species of the genus Homo, which lived Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus ^[2][3][4] This, however, is the suggested result of evolution from Homo erectus (around 1 mya) via a series of intermediate anthropoid stages, and is therefore a much more complicated link. Homo erectus ( Latin: "upright man" is an extinct species of the genus Homo, believed to have been the first hominin In Astronomy, Geology, and Paleontology, mya or " mya " is an abbreviation for "million years ago". The simians ( Infraorder Simiiformes) are the "higher Primates quot familiar to most people the Monkeys and the Apes including

The most important factors leading to the habile hand (and its thumb) are:

• the freeing of the hands from their walking requirements—still so crucial for apes today, as they have hands for feet, which in its turn was one of the consequences of the gradual pithecanthropoid and anthropoid adoption of the erect bipedal walking gait, and
• the simultaneous development of a larger anthropoid brain in the later stages. Bipedalism is a form of Terrestrial locomotion where an organism moves by means of its two rear limbs Walking (also called ambulation) is the main form of Animal Locomotion on land, distinguished from Running and crawling The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain

It is possible though that a more likely scenario may be that the specialized, precision gripping hand (equipped with opposable thumb) of Homo habilis preceded walking, with the specialized adaptation of the spine, pelvis and lower extremities proceeding a more advanced hand. Homo habilis (ˈhoʊmoʊ ˈhæbəlɪs ("handy man" "skillful person" is a Species of the genus Homo, which lived And, it is logical that a conservative, highly functional adaptation be followed by a series of more complex ones that complement it. With Homo habilis an advanced grasping-capable hand was accompanied by facultative bipedalism, possibly implying, assuming a co-opted evolutionary relationship exists, that the latter resulted from the former as obligate bipedalism was yet to follow. Homo habilis (ˈhoʊmoʊ ˈhæbəlɪs ("handy man" "skillful person" is a Species of the genus Homo, which lived Bipedalism is a form of Terrestrial locomotion where an organism moves by means of its two rear limbs ^[5] Walking may have been a byproduct of busy hands and not vice versa.

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 fine motor skills. Fine motor skills can be defined as coordination of small Muscle movements which occur e It is also thought to have directly led to the development of tools, not just in humans or their evolutionary ancestors, but other primates as well. The opposable thumb ensured that writing was possible. ^[6][7] The thumb, in conjunction with the other fingers make humans and other species with similar hands some of the most dexterous in the world. ^[8]

Other animals with thumbs

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

• Orangutan - opposable thumbs on both hands and both feet. The orangutans are two Species of great apes known for their intelligence long arms and reddish-brown hair The interdigital grip gives them the ability to pick fruit.
• Gorillas-opposable on both hands and both feet. Gorillas, the largest of the living Primates are ground-dwelling Herbivores that inhabit the Forests of Africa.
• Chimpanzees have opposable thumbs on both hands and both feet. Chimpanzee (often shortened to chimp) is the common name for the two extant Species of Apes in the Genus Pan.
• Lesser Apes have opposable thumbs on both hands and both feet. Gibbons are the small Apes in the family Hylobatidae. The family is divided into four genera based on their Diploid Chromosome
• Old World Monkeys, with some exceptions, such as the genera, Piliocolobus and Colobus. The Old World monkeys or Cercopithecidae are a group of Primates falling in the Superfamily Cercopithecoidea in the Clade The red colobus are Old World monkeys of the genus Piliocolobus. Black-and-white colobus are Old World monkeys of the genus Colobus and are closely related to the Red colobus monkeys of genus
• Cebids (New World primates of Central and South America) - some have opposable thumbs. The Cebidae form one of the four families of New World monkeys now recognised
• Koala - opposable toe on each foot, plus two opposable digits on each hand. The Koala (Phascolarctos cinereus is a thickset Arboreal Marsupial herbivore native to Australia, and the only extant Toes are the digits of the Foot of an animal Many animal species such as Cats walk on their toes and are described as being Digitigrade
• Opossum - opposable thumb on rear feet. Didelphimorphia is the order of common opossums of the Western Hemisphere.
• Giant Panda - Panda paws have five clawed fingers plus an extra bone that works like an opposable thumb. The Giant Panda ( Ailuropoda melanoleuca, "black-and-white cat-foot" is a Mammal classified in the Bear family ( Ursidae) native to This "thumb" is not really a finger (like the human thumb is), but an extra-long sesamoid bone that works like a thumb. In Anatomy, a sesamoid bone is a Bone embedded within a Tendon.
• Troodon - a birdlike dinosaur with partially opposable thumbs. Troodon (or Troödon in older sources is a Genus of relatively small Bird -like Dinosaur from the Late Cretaceous
• Bambiraptor - a small, predatory dinosaur, was able to touch the outer two of its three digits together in an opposable grip. Bambiraptor is a 75 million year old bird-like Dinosaur discovered by scientists at the University of Kansas, Yale University

See also

• Adducted thumb syndrome
• Clubbed thumb
• Thumbing
• Thumb twiddling
• Thumb sucking
• Thumb ring
• Thumb wrestling
• List of Mendelian traits in humans

References

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