A hand (med. Medicine is the science and art of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness. Before scientific medicine, healing arts were practised in accordance with alchemical treatments and ritual practices that developed out of religious and cultural traditions/lat. Latin or sometimes Roman is an Italic language originally spoken in Latium and Ancient Rome. Although often considered a dead language, in view of the fact that it has no native, fluent speakers, Latin continues to be taught in schools and has been, and currently is, used in the process of new word production in modern languages from many: manus, pl. manūs) is a prehensile Prehensility is the quality of an appendage or organ that has adapted for grasping or holding. The word is derived from the Latin term prehendere, meaning "to grasp.", multi-fingered 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, termed phalanges, on each hand . The first digit is the thumb, followed by index finger, middle finger, ring finger, and little finger or pinky. Some other languages use the same generic term for body part located at the end of an arm or forelimb of primates A primate is a member of the biological order Primates (/praɪˈmeɪtiːz/ prī·mā′·tēz; Latin: "prime, first rank"), the group that contains prosimians (including lemurs, lorises, galagos and tarsiers ) and simians (monkeys and apes). With the exception of humans, who inhabit every continent on Earth,[a] most primates live in and some^[which?] other vertebrates Vertebrates are members of the subphylum Vertebrata, chordates with backbones or spinal columns. About 58,000 species of vertebrates have been described. Vertebrata is the largest subphylum of chordates, and contains many familiar groups of large land animals. Vertebrates comprise cyclostomes, bony fish, sharks and rays, amphibians, reptiles,.

Hands are the chief organs for physically manipulating the environment, used for both gross motor skills The term gross motor skills refers to the abilities usually acquired during infancy and early childhood as part of a child's motor development. By the time they reach two years of age, almost all children are able to stand up, walk and run, walk up stairs, etc. These skills are built upon, improved and better controlled throughout early childhood, (such as grasping a large object) and fine motor skills Fine motor skills are the coordination of small muscle movements which occur e.g., in the fingers, usually in coordination with the eyes. In application to motor skills of hands the term dexterity is commonly used (such as picking up a small pebble). The fingertips contain some of the densest areas of nerve endings on the body, are the richest source of tactile The somatosensory system is a diverse sensory system comprising the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception (pain). The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal organs, and the cardiovascular system. While feedback, and have the greatest positioning capability of the body; thus the sense of touch The somatosensory system is a diverse sensory system comprising the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception (pain). The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal organs, and the cardiovascular system. While is intimately associated with hands. Like other paired organs (eyes, ears, legs), each hand is dominantly controlled by the opposing brain hemisphere A cerebral hemisphere is defined as one of the two regions of the brain that are delineated by the body's median plane, (medial longitudinal fissure). The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter called the cerebral cortex that is supported by, and thus handedness Handedness is an attribute of humans defined by their unequal distribution of fine motor skill between the left and right hands. An individual who is more dexterous with the right hand is called right-handed, and one who is more skilled with the left is said to be left-handed. A minority of people are equally skilled with both hands, and are, or preferred hand choice for single-handed activities such as writing with a pen, reflects a significant individual trait.

Some evolutionary anatomists Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy (zootomy) and plant anatomy (phytotomy). In some of its facets anatomy is closely related to embryology, comparative anatomy and comparative embryology, through common roots in use hand to refer more generally to the appendage of digits on the forelimb, for example, in the context of whether the three digits A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates of the bird Birds are winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. There are around 10,000 living species, making them the most varied of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.75 m (9 ft) Ostrich hand involved the same homologous In evolutionary biology, homology refers to any similarity between characteristics of organisms that is due to their shared ancestry. The word homologous derives from the ancient Greek ομολογειν, 'to agree'. There are examples in different branches of biology. Anatomical structures that perform the same function in different biological loss of two digits as in the dinosaur Dinosaurs are a diverse group of reptiles. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous period (about 65 million years ago), when the Cretaceous–Tertiary extinction event caused the extinction of most dinosaur species, except for some birds. The fossil hand.^[1]

Definitions

Many mammals Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not and other animals Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. All animals are also have grasping appendages similar in form to a hand such as paws A paw is the soft foot of a mammal, generally a quadruped, that has claws or nails. A hard foot is called a hoof. Paws are used to pad feet for walking and increase friction, claws A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end of the leg or tarsus for gripping a, and talons, but these are not scientifically considered to be grasping hands. The scientific use of the term hand in this sense to distinguish the terminations of the front paws from the hind ones is an example of anthropomorphism Anthropomorphism is the attribution of human characteristics to non-human animal or non-living things, phenomena, material states and objects or abstract concepts. Examples include animals and plants and forces of nature such as winds, rain or the sun depicted as creatures with human motivations, and/or the abilities to reason and converse. The. The only true grasping hands appear in the mammalian order of primates A primate is a member of the biological order Primates (/praɪˈmeɪtiːz/ prī·mā′·tēz; Latin: "prime, first rank"), the group that contains prosimians (including lemurs, lorises, galagos and tarsiers ) and simians (monkeys and apes). With the exception of humans, who inhabit every continent on Earth,[a] most primates live in. Hands must also have opposable thumbs The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit. The Medical Latin English adjective for thumb is pollical, as described later in the text.

Humans have two hands located at the distal end of each arm. Apes An ape is any member of the Hominoidea superfamily of primates, including humans. Due to its ambiguous nature, the term ape has been deemphasized in favor of Hominoidea as a means of describing taxonomic relationships and monkeys A monkey is any cercopithecoid or platyrrhine (New World monkey) primate. All primates that are not prosimians (lemurs and tarsiers) or apes are monkeys. The 264 known extant monkey species represent two of the three groupings of simian primates (the third group being the 21 species of apes). Monkeys are generally considered to be intelligent and, are sometimes described as having four hands, because the toes are long and the hallux In tetrapods the hallux is the innermost toe of the foot. Despite its name it may not be the longest toe on the foot of some individuals. It is counted as digit I (one). The name stems from the Latin for the same, similar to the pollex, which refers to the thumb, the corresponding digit of the hand. The hallux is considered to be the most is opposable and looks more like a thumb The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit. The Medical Latin English adjective for thumb is pollical, thus enabling the feet to be used as hands. Also, some apes have toes that are longer than human fingers.^[2]

The word "hand" is sometimes used by evolutionary anatomists to refer to the appendage of digits on the forelimb such as when researching the homology between the three digits A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates of the bird Birds are winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. There are around 10,000 living species, making them the most varied of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.75 m (9 ft) Ostrich hand and the dinosaur Dinosaurs are a diverse group of reptiles. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous period (about 65 million years ago), when the Cretaceous–Tertiary extinction event caused the extinction of most dinosaur species, except for some birds. The fossil hand.^[1]

Human anatomy

The human hand consists of a broad palm (metacarpus) with 5 digits, attached to the forearm by a joint called the wrist (carpus).^[3][4] The back of the hand is formally called the dorsum of the hand.

Digits

The four fingers 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, termed phalanges, on each hand . The first digit is the thumb, followed by index finger, middle finger, ring finger, and little finger or pinky. Some other languages use the same generic term for on the hand are used for the outermost performance; these four digits can be folded over the palm which allows the grasping of objects. Each finger, starting with the one closest to the thumb, has a colloquial name to distinguish it from the others:

• index finger The index finger, , is the first finger and the second digit of a human hand (med. Medicine is the science and art of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness. Before scientific medicine, healing arts were practised in accordance with alchemical treatments and ritual practices that developed out of religious and cultural traditions/lat. Latin or sometimes Roman is an Italic language originally spoken in Latium and Ancient Rome. Although often considered a dead language, in view of the fact that it has no native, fluent speakers, Latin continues to be taught in schools and has been, and currently is, used in the process of new word production in modern languages from many:digitus secundus manus), pointer finger, or forefinger
• middle finger The middle finger is the third digit of the human hand, located between the index finger and the ring finger. It is also called the third finger, digitus medius, digitus tertius, "digitus infamous", or digitus III in anatomy (digitus médius and more commonly digitus tertius)
• ring finger According to László A. Magyar, the names of the ring finger in many languages reflect an ancient belief that it is a magical finger. It is named after magic or rings, or called nameless (digitus annuláris) - Annulus
• little finger The little finger, often called the pinky in American English and pinkie in Scottish English , is the most ulnar and usually smallest finger of the human hand, opposite the thumb, next to the ring finger (digitus mínimus mánus) or 'pinky' - minimus

The thumb The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit. The Medical Latin English adjective for thumb is pollical (connected to the trapezium The trapezium is distinguished by a deep groove on its palmar surface. It is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone. It is homologous with the first distal carpal of reptiles and amphibians) is located on one of the sides, parallel to the arm. The thumb can be easily rotated 90°, on a level perpendicular to the palm, unlike the other fingers which can only be rotated approximately 45°^{[citation needed]}. A reliable way of identifying true hands is from the presence of opposable thumbs The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit. The Medical Latin English adjective for thumb is pollical. Opposable thumbs are identified by the ability to be brought opposite to the fingers, a muscle action known as opposition The movement of body structures is accomplished by the contraction of muscles. Muscles may move parts of the skeleton relatively to each other, or may move parts of internal organs relatively to each other. All such movements are classified by the directions in which the affected structures are moved. In human anatomy, all descriptions of position.

Bones

The human hand has 27 bones: the carpus or wrist account for 8; the metacarpals In human anatomy, the metacarpus is the intermediate part of the hand skeleton that is located between the phalanges distally and the carpus which forms the connection to the forearm. The metacarpus consists of metacarpal bones. Its equivalent in the foot is the metatarsus or palm contains five; the remaining fourteen are digital bones; fingers and thumb

The eight bones of the wrist are arranged in two rows of four. These bones fit into a shallow socket formed by the bones of the forearm. The bones of proximal row are (from lateral to medial): scaphoid The scaphoid bone is one of the carpal bones of the wrist. It situated between the hand and forearm on the thumb-side of the wrist . The scaphoid bone is the largest bone of the proximal row of wrist bones, its long axis being from above downward, lateralward, and forward. It is approximately the size and shape of a medium sized cashew, lunate, triquetral The triquetral bone is located in the wrist on the medial side of the proximal row of the carpus between the lunate and pisiform bones. It is on the ulnar side of the hand, but does not articulate with the ulna. It connects with the pisiform, hamate, and lunate bones. It is the 3rd most commonly fractured carpal bone and pisiform The pisiform bone is found in the proximal row of the carpus. It is located where the ulna joins the carpus (wrist). It articulates only with the triquetral. The bones of the distal row are (from lateral to medial): trapezium The trapezium is distinguished by a deep groove on its palmar surface. It is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone. It is homologous with the first distal carpal of reptiles and amphibians, trapezoid The trapezoid bone is a carpal bone in tetrapods, including humans. It is the smallest bone in the distal row. It may be known by its wedge-shaped form, the broad end of the wedge constituting the dorsal, the narrow end the palmar surface; and by its having four articular facets touching each other, and separated by sharp edges, capitate The capitate bone is a bone in the human hand. The capitate bone is the largest of the carpal bones, and occupies the center of the wrist. It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and lunate bones; a constricted portion or neck; and below this, the body. The bone is also found in and hamate.

The palm has five bones known as metacarpal bones, one to each of the 5 digits. These metacarpals have a head, a shaft, and a base.

Human hands contain fourteen digital bones, also called phalanges, or phalanx bones In anatomy, phalanx bones are those that form the 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: two in the thumb (the thumb has no middle phalanx) and three in each of the four fingers. These are the distal phalanx, carrying the nail, the middle phalanx, and the proximal phalanx.

Sesamoid bones are small ossified nodes embedded in the tendons to provide extra leverage and reduce pressure on the underlying tissue. Many exist around the palm at the bases of the digits; the exact number varies between different people.

Articulations

Also of note is that the articulation of the human hand is more complex and delicate than that of comparable organs in any other animals. Without this extra articulation, we would not be able to operate a wide variety of tools and devices. The hand can also form a fist, for example in combat, or as a gesture.

The articulations are:

• interphalangeal articulations of hand
• metacarpophalangeal joints
• intercarpal articulations
• wrist (may also be viewed as belonging to the forearm.)

Muscles and tendons

The movements of the human hand are accomplished by two sets of each of these tissues. They can be subdivided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscle groups are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm.

The intrinsic muscle groups are the thenar and hypothenar muscles (thenar referring to the thumb, hypothenar to the small finger), the interossei muscles (between the metacarpal bones, four dorsally and three volarly) and the lumbrical muscles. These muscles arise from the deep flexor (and are special because they have no bony origin) and insert on the dorsal extensor hood mechanism. The intrinsic muscles of hand can be remembered using the mnemonic, "A OF A OF A" for, Abductor pollicis brevis, Opponens pollicis, Flexor pollicis brevis, Adductor pollicis (thenar muscles) and Opponens digiti minimi, Flexor digiti minimi brevis, Abductor digiti minimi (hypothenar muscles).^[5]

The fingers have two long flexors, located on the underside of the forearm. They insert by tendons to the phalanges of the fingers. The deep flexor attaches to the distal phalanx, and the superficial flexor attaches to the middle phalanx. The flexors allow for the actual bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group. The human thumb also has other muscles in the thenar group (opponens and abductor brevis muscle), moving the thumb in opposition, making grasping possible.

The extensors are located on the back of the forearm and are connected in a more complex way than the flexors to the dorsum of the fingers. The tendons unite with the interosseous and lumbrical muscles to form the extensorhood mechanism. The primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm; the tendons of these form the anatomical snuff box. Also, the index finger and the little finger have an extra extensor, used for instance for pointing. The extensors are situated within 6 separate compartments. The 1st compartment contains abductor pollicis longus and extensor pollicis brevis. The 2nd compartment contains extensors carpi radialis longus and brevis. The 3rd compartment contains extensor pollicis longus. The extensor digitorum indicis and extensor digititorum communis are within the 4th compartment. Extensor digiti minimi is in the fifth, and extensor carpi ulnaris is in the 6th.

Sexual dimorphism

The average length of an adult male hand is 189 mm, while the average length of an adult female hand is 172 mm. The average hand breadth for adult males and females is 84 and 74 mm respectively.^[6]

Disorders and diseases

• Polymelia, a birth defect in which the individual has more than the usual number of limbs.^[7]
• Some people have more than the usual number of fingers or toes, a condition called polydactyly.^[8] Others may have more than the typical number of metacarpal bones, a condition often caused by genetic disorders like Catel-Manzke syndrome.
• Hand infection
• Hand surgery
• Carpal Tunnel Syndrome

Additional images

See also

• Dermatoglyphics
• Hand fetishism
• Hand strength
• Hand walking
• Handanalysis
• Handstand
• Knuckle-walking

References

1. ^ ^{a b} Xing Xu et al.(2009). A Jurassic ceratosaur from China helps clarify avian digital homologies. Nature 459: 940-944 doi:10.1038/nature08124
2. ^ "Primate Feet". ufovideo.net. http://www.ufovideo.net/BIGFOOTxSASQUATCHxHandsxFeetxlarge.jpg. Retrieved December 2009. (JPG)
3. ^ "Nature Bulletin No. 611". Division of Educational Programs, Argonne National Laboratory. 1960-10-01. http://www.newton.dep.anl.gov/natbltn/600-699/nb611.htm. Retrieved 2007-12-24.
4. ^ "hand". Oxford English Dictionary. Oxford University Press. 2nd ed. 1989.
5. ^ "Medical mnemonics". LifeHugger. http://mc.lifehugger.com/moc/386/intrinsic-muscles-hand. Retrieved 2009-12-19.
6. ^ Agnihotri, A. K.; B. Purwar, N. Jeebun, S. Agnihotri (2006). Determination Of Sex By Hand Dimensions. 1. The Internet Journal of Forensic Science. http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ijfs/vol1n2/hand.xml. Retrieved 2007-12-24.
7. ^ "Three-armed boy to have surgery". BBC News. 2006-05-31. http://news.bbc.co.uk/1/hi/health/5032906.stm. Retrieved 2007-12-24.
8. ^ "Polydactyly and Syndactyly". Milton S. Hershey Medical Center, Pennsylvania State University. http://www.hmc.psu.edu/healthinfo/pq/poly.htm. Retrieved 2007-12-24.

External links

• Hand injuries and diseases (Handuniversity.com)
• Hand anatomy (eMedicine)

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