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Thumb
The 'thumbs up' gesture is a sign of approval in many cultures, and an obscene gesture in many others.
Latinpollex, digitus primus, digitus I
Arteryprinceps pollicis artery
Lymphinfraclavicular lymph nodes[1]
MeSH Thumb
Dorlands/Elsevier p_27/12655361


The thumb is one of the five fingers.

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):

NameLocationNerve
extensor pollicis longusforearmposterior interosseous nerve
abductor pollicis longusforearmposterior interosseous nerve
flexor pollicis longusforearmanterior interosseous nerve
extensor pollicis brevisforearmposterior interosseous nerve
abductor pollicis brevishandmedian nerve
flexor pollicis brevishandmedian nerve
opponens pollicishandmedian nerve
adductor pollicishandulnar 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.

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:
  1. Any of the five digits.
  2. 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:
  • 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.

Origin of the thumb

The evolution of the opposable or prehensile thumb is usually associated with Homo habilis, the forerunner of Homo sapiens.[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.

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.

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. 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 [5][6]. The thumb, in conjunction with the other fingers make humans and other species with similar hands some of the most dexterous in the world[7].

Other animals with thumbs

Many animals, primates and others, also have some kind of opposable thumb or toe:
  • Bornean Orangutan - opposable thumbs on all four hands. The interdigital grip gives them the ability to pick fruit.
  • Gorillas-opposable on all four hands.
  • Chimpanzees have opposable thumbs on all four hands.
  • Lesser Apes have opposable thumbs on all four hands.
  • Old World Monkeys, with some exceptions, such as the genera, Piliocolobus and Colobus.
  • Cebids (New World primates of Central and South America) - some have opposable thumbs
  • Koala - opposable toe on each foot, plus two opposable digits on each hand
  • Opossum - opposable thumb on rear feet
  • Giant Panda - Panda paws have five clawed fingers plus an extra bone that works like an opposable thumb. This "thumb" is not really a finger (like the human thumb is), but an extra-long sesamoid bone that works like a thumb.
  • Troodon - a birdlike dinosaur with partially opposable thumbs.
  • Raccoon - a common mammal with thumbs, which are not opposables.

See also

References

1. ^ Norman/Georgetown clinicalconsiderations
2. ^ [1]
3. ^ [2]
4. ^ [3]
5. ^ [4] Lesson Plans - Chimps, Humans, Thumbs, and Tools]National Geographic, 2006, accessed April 26, 2007
6. ^ Damonte, Kathleen Thumbs Are Handy DigitsNational Science Teachers Association: Science & Children: The Elementary Science Classroom. February 2004, accessed April 26, 2007
7. ^ Chaisson, Eric J. Cosmic Evolution - Epoch 6 - Biological Evolution. Tufts University. 2007, accessed April 26, 2007


 •  • [ e]
Human anatomical features
HEAD: Skull - Forehead – Eye – Ear – Nose – Mouth – Tongue – Teeth – Jaw – Face – Cheek – Chin NECK: Throat - Larynx – Adam's apple TORSO: Shoulders – Spine – Breast – Chest – Ribcage – Abdomen – Navel
:Sex organs (Clitoris/Vagina/Ovary/Uterus/Penis/Scrotum/Testicle) – Hip – Anus – Buttocks
LIMBS: Arm – Elbow – Forearm – Wrist – Hand – Finger (Thumb/Index/Middle/Ring/Little) – Leg – Lap – Thigh – Knee – Calf – Heel – Ankle – Foot – Toe (Hallux) SKIN: Hair
thumbs up or thumbs down is a common gesture represented by a closed fist held with the thumb extended upward or downward in approval or disapproval respectively.
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gesture is a form of non-verbal communication made with a part of the body, used instead of or in combination with verbal communication. The language of gesture allows individuals to express a variety of feelings and thoughts, from contempt and hostility to approval and
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Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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Arteries are muscular blood vessels that carry blood away from the heart.[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
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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 first dorsal interosseous muscle and the oblique head of the adductor pollicis, along the medial side of
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The lymphatic system is a complex network of lymphoid organs, lymph nodes, lymph ducts, lymphatic tissues, lymph capillaries and lymph vessels that produce and transport lymph fluid from tissues to the circulatory system.
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One or two deltopectoral lymph nodes (or infraclavicular nodes) are found beside the cephalic vein, between the Pectoralis major and Deltoideus, immediately below the clavicle.

They are situated in the course of the external collecting trunks of the arm.
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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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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).
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In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. Non-scientists often wonder why zoological and human anatomists use complex terminology to describe locations on a body, when common terms like "up",
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Phalanges is commonly given to the bones that form fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.
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In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. Non-scientists often wonder why zoological and human anatomists use complex terminology to describe locations on a body, when common terms like "up",
..... Click the link for more information.
The metacarpus is the intermediate part of the hand skeleton that is located between the fingers distally and the carpus which forms the connection to the forearm.

Specific metacarpals


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The Extensor pollicis longus is much larger than the Extensor pollicis brevis muscle, the origin of which it partly covers.

Origin and insertion

It arises from the lateral part of the middle third of the dorsal surface of the body of the ulna below the origin of the
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posterior interosseous nerve (or dorsal interosseous nerve), on the interosseous membrane, in front of the Extensor pollicis longus, to the back of the carpus, where it presents a gangliform enlargement from which filaments are distributed to the ligaments and articulations
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The Abductor pollicis longus lies immediately below the Supinator and is sometimes united with it.

Origin and insertion

It arises from the lateral part of the dorsal surface of the body of the ulna below the insertion of the Anconæus, from the interosseous membrane, and
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posterior interosseous nerve (or dorsal interosseous nerve), on the interosseous membrane, in front of the Extensor pollicis longus, to the back of the carpus, where it presents a gangliform enlargement from which filaments are distributed to the ligaments and articulations
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The flexor pollicis longus is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus.

Origin and insertion


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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 ulnar half of the flexor digitorum profundus.
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The Extensor pollicis brevis lies on the medial side of, and is closely connected with, the Abductor pollicis longus.

Origin and insertion

It arises from the dorsal surface of the body of the radius below that muscle, and from the interosseous membrane.
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posterior interosseous nerve (or dorsal interosseous nerve), on the interosseous membrane, in front of the Extensor pollicis longus, to the back of the carpus, where it presents a gangliform enlargement from which filaments are distributed to the ligaments and articulations
..... Click the link for more information.
The abductor pollicis brevis is a muscle in the hand that functions as an abductor of the thumb.

Structure

The abductor pollicis brevis is a flat, thin muscle located just under the skin.
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The median nerve is a nerve that runs down the arm and forearm. It is one of the five main nerves originating from the brachial plexus.

The median nerve is formed from parts of the medial and lateral cords of the brachial plexus, and continues down the arm to enter the
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The flexor pollicis brevis is a muscle in the hand that flexes the thumb. It is one of three thenar muscles. It has both a superficial part and a deep part.

The superficial part arises from the distal edge of the flexor retinaculum of the hand and the tubercle of the
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The median nerve is a nerve that runs down the arm and forearm. It is one of the five main nerves originating from the brachial plexus.

The median nerve is formed from parts of the medial and lateral cords of the brachial plexus, and continues down the arm to enter the
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The opponens pollicis is a small, triangular muscle in the hand, which functions to oppose the thumb. It is one of the three thenar muscles, lying deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis.
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The median nerve is a nerve that runs down the arm and forearm. It is one of the five main nerves originating from the brachial plexus.

The median nerve is formed from parts of the medial and lateral cords of the brachial plexus, and continues down the arm to enter the
..... Click the link for more information.
The adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique.

Structure

Oblique head

The oblique head (occasionally known as adductor obliquus pollicis
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In human anatomy, the ulnar nerve is a nerve which runs from the shoulder to the hand, at one part running near the ulna bone. It is the only exposed nerve in the human body (it is unprotected for a few centimeters at the elbow).
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