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88-422: A hand is a prehensile , multi- fingered appendage located at the end of the forearm or forelimb of primates such as humans , chimpanzees , monkeys , and lemurs . A few other vertebrates such as the koala (which has two opposable thumbs on each "hand" and fingerprints extremely similar to human fingerprints ) are often described as having "hands" instead of paws on their front limbs. The raccoon

176-465: A dermatologist with a focus in this particular area of medicine. However, most times it is a nail stylist who will note a subtle change in nail disease. Inherited accessory nail of the fifth toe occurs where the toenail of the smallest toe is separated, forming a smaller "sixth toenail" in the outer corner of the nail. Like any other nail, it can be cut using a nail clipper . Finger entrapment injuries are common in children and can include damage to

264-481: A central ridge that ends in a needle-like tip. A study of the fingertip morphology of four small-bodied New World monkey species indicated a correlation between increasing small-branch foraging and: This suggests that whereas claws are useful on large-diameter branches, wide fingertips with nails and epidermal ridges were required for habitual locomotion on small-diameter branches. It also indicates keel-shaped nails of Callitrichines (a family of New World monkeys)

352-545: A cursory indicator of distal tissue perfusion of individuals who may be dehydrated or in shock . However, this test is not considered reliable in adults. This is known as the CRT or blanch test . The fingernail bed is briefly depressed to turn the nail-bed white. When the pressure is released, the normal pink colour should be restored within a second or two. Delayed return to pink color can be an indicator of certain shock states such as hypovolemia . Nail growth record can show

440-437: A high-gloss finish and last for two to three weeks. Nail wraps are formed by cutting pieces of fiberglass , linen , silk fabric, or another material to fit on the surface of the nail (or a tip attached prior), to be sealed onto the nail plate with a layer of resin or glue. They do not damage the nail and also provide strength to the nail but are not used to lengthen it. It can also be used to fix broken nails. The treatment

528-399: A higher degree, the hands of other primates are anatomically similar and the dexterity of the human hand can not be explained solely on anatomical factors. The neural machinery underlying hand movements is a major contributing factor; primates have evolved direct connections between neurons in cortical motor areas and spinal motoneurons , giving the cerebral cortex monosynaptic control over

616-418: A large role in healthy skin as well as nails. Splitting and flaking of nails may be due to a lack of linoleic acid . Iron-deficiency anemia can lead to a pale color along with a thin, brittle, ridged texture. Iron deficiency in general may cause the nails to become flat or concave, rather than convex. As oxygen is needed for healthy nails, an iron deficiency or anemia can lead to vertical ridges or concavity in

704-400: A multitude of functions—including climbing, digging, and fighting—and have undergone numerous adaptive changes in different animal taxa . Claws are pointed at their ends and are composed of two layers: a thick, deep layer and a superficial, hardened layer which serves a protective function. The underlying bone is a virtual mold of the overlying horny structure and therefore has the same shape as

792-523: A pencil—reflects individual brain functioning. Among humans, the hands play an important function in body language and sign language . Likewise, the ten digits of two hands and the twelve phalanges of four fingers (touchable by the thumb) have given rise to number systems and calculation techniques. Many mammals and other animals have grasping appendages similar in form to a hand such as paws , claws , and talons, but these are not scientifically considered to be grasping hands. The scientific use of

880-415: A pink color. The lunula ("small moon") is the visible part of the matrix, the whitish crescent-shaped base of the visible nail. The lunula can best be seen in the thumb and may not be visible in the little finger. The lunula appears white due to a reflection of light at the point where the nail matrix and nail bed meet. The nail bed is the skin beneath the nail plate. It is the area of the nail on which

968-457: A primitive trait, while the palms of other extant higher primates are elongated to the extent that some of the thumb's original function has been lost (most notably in highly arboreal primates such as the spider monkey ). In humans, the big toe is thus more derived than the thumb. There is a hypothesis suggesting the form of the modern human hand is especially conducive to the formation of a compact fist, presumably for fighting purposes. The fist

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1056-426: A transitional element to the fifth metacarpal. Together with the thumb, the four fingers form four oblique arches, of which the arch of the index finger functionally is the most important, especially for precision grip, while the arch of the little finger contribute an important locking mechanism for power grip. The thumb is undoubtedly the "master digit" of the hand, giving value to all the other fingers. Together with

1144-429: Is a small band of living cells ( epithelium ) that extends from the posterior nail wall onto the base of the nail. The eponychium is the end of the proximal fold that folds back upon itself to shed an epidermal layer of skin onto the newly formed nail plate. The perionyx is the projecting edge of the eponychium covering the proximal strip of the lunula. The nail wall ( vallum unguis ) is the cutaneous fold overlapping

1232-431: Is compact and thus effective as a weapon. It also provides protection for the fingers. However, this is not widely accepted to be one of the primary selective pressures acting on hand morphology throughout human evolution, with tool use and production being thought to be far more influential. Prehensile Prehensility is the quality of an appendage or organ that has adapted for grasping or holding. The word

1320-404: Is dependent upon age, sex, season, exercise level, diet, and hereditary factors. The longest female nails known ever to have existed measured a total of 8.65 m (28 ft 4.5 in). Contrary to popular belief, nails do not continue to grow after death; the skin dehydrates and tightens, making the nails (and hair ) appear to grow. The nail is often considered an impermeable barrier, but this

1408-624: Is derived from the Latin term prehendere , meaning "to grasp". The ability to grasp is likely derived from a number of different origins. The most common are tree-climbing and the need to manipulate food. Appendages that can become prehensile include: Prehensility affords animals a great natural advantage in manipulating their environment for feeding, climbing, digging , and defense. It enables many animals, such as primates, to use tools to complete tasks that would otherwise be impossible without highly specialized anatomy. For example, chimpanzees have

1496-401: Is highly innervated, and removal of the nail plate is often excruciatingly painful as a result. The nail sinus ( sinus unguis ) is where the nail root is; i.e. the base of the nail underneath the skin. It originates from the actively growing tissue below, the matrix. The nail plate ( corpus unguis ) sometimes referred to as the nail body, is the visible hard nail area from the nail root to

1584-451: Is however more expensive. With the dip powder method, a clear liquid is brushed onto a nail and the nail is then placed into pigmented powder. Dip nails tend to last about a month, 2–3 weeks longer than gel and acrylic nails. It can be worn on natural nails, or with tips to create an artificial nail. Dip powder nails do not require any UV/LED light to be cured, instead they are sealed using an activator. The quickest way to remove dip powder

1672-473: Is located on one of the sides, parallel to the arm. A reliable way of identifying human hands is from the presence of opposable thumbs. Opposable thumbs are identified by the ability to be brought opposite to the fingers, a muscle action known as opposition. The skeleton of the human hand consists of 27 bones: the eight short carpal bones of the wrist are organized into a proximal row ( scaphoid , lunate , triquetral and pisiform ) which articulates with

1760-583: Is mixed with a liquid monomer (usually ethyl methacrylate mixed with some inhibitor) it forms a malleable bead. This mixture begins to cure immediately, continuing until completely solid in minutes. Acrylic nails can last up to 21 days but can last longer with touch-ups. To give acrylic nails color, gel polish, nail polish, and dip powders can be applied. Gel nails can be used in order to create artificial nail extensions, but can also be used like nail polish. They are hardened using ultraviolet light. They last longer than regular nail polish and do not chip. They have

1848-413: Is not true. In fact, it is much more permeable than the skin, and the composition of the nail includes 7–12% water. This permeability has implications for penetration by harmful and medicinal substances; in particular cosmetics applied to the nails can pose a risk. Water can penetrate the nail as can many other substances including paraquat , a fast acting herbicide that is harmful to humans, urea which

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1936-410: Is often an ingredient in creams and lotions meant for use on hands and fingers, and several fungicidal agents such as salicylic acid , miconazole branded Monistat, natamycin ; and sodium hypochlorite which is the active ingredient in common household bleach (but usually only in 2–3% concentration). Healthcare and pre-hospital-care providers ( EMTs or paramedics ) often use the fingernail beds as

2024-473: Is quite subjective. Both vitamin B12 and folate play a role in red blood cell production and oxygen transportation to nail cells. Inadequacies can result in discoloration of the nails. Diminished dietary intake of omega-3 fatty acids may contribute to dry and brittle nails. Protein is a building material for new nails; therefore, low dietary protein intake may cause anemia and the resultant reduced hemoglobin in

2112-407: Is supplemented by the precision grip between the thumb and the distal finger pads made possible by the opposable thumbs. Hominidae (great apes including humans) acquired an erect bipedal posture about 3.6  million years ago , which freed the hands from the task of locomotion and paved the way for the precision and range of motion in human hands. Functional analyses of the features unique to

2200-408: Is the anterior margin of the nail plate corresponds to the abrasive or cutting edge of the nail. The hyponychium (informally known as the "quick") is the epithelium located beneath the nail plate at the junction between the free edge and the skin of the fingertip. It forms a seal that protects the nail bed. The onychodermal band is the seal between the nail plate and the hyponychium. It is just under

2288-450: Is to cut, shape and care for nails as well as to apply overlays such as acrylic and UV gel is sometimes called a nail stylist . The place where a nail stylist works may be a nail salon or nail shop or nail bar. Painting the nails with colored nail polish (also called nail lacquer and nail varnish) to improve the appearance is a common practice dating back to at least 3000 BC. Acrylic nails are made out of acrylic glass ( PMMA ). When it

2376-408: Is to drill, clip off, or buff out layers of the powder so, when they are soaking in acetone , they slide right off. Guinness World Records began tracking record fingernail lengths in 1955, when a Chinese priest was listed as having fingernails 1 foot 10.75 inches (57.79 cm) long. The current record-holder for men, according to Guinness , is Shridhar Chillal from India who set

2464-497: Is to the neck of a metacarpal. One can also have a broken finger . The prehensile hands and feet of primates evolved from the mobile hands of semi- arboreal tree shrews that lived about 60  million years ago . This development has been accompanied by important changes in the brain and the relocation of the eyes to the front of the face, together allowing the muscle control and stereoscopic vision necessary for controlled grasping. This grasping, also known as power grip,

2552-1005: Is to trim them regularly. Filing is also recommended, as to keep nails from becoming too rough and to remove any small bumps or ridges that may cause the nail to get tangled up in materials such as cloth . Bluish or purple fingernail beds may be a symptom of peripheral cyanosis , which indicates oxygen deprivation. Nails can dry out, just like skin . They can also peel, break, and be infected . Toe infections, for instance, can be caused or exacerbated by dirty socks , specific types of aggressive exercise ( long-distance running ), tight footwear , and walking unprotected in an unclean environment . Common organisms causing nail infections include yeasts and molds (particularly dermatophytes ). Nail tools used by different people may transmit infections. Standard hygiene and sanitation procedures avoid transmission. In some cases, gel and cream cuticle removers can be used instead of cuticle scissors. Nail disease can be very subtle and should be evaluated by

2640-501: Is usually described as having "hands" though opposable thumbs are lacking. Some evolutionary anatomists use the term hand to refer to the appendage of digits on the forelimb more generally—for example, in the context of whether the three digits of the bird hand involved the same homologous loss of two digits as in the dinosaur hand. The human hand usually has five digits: four fingers plus one thumb ; these are often referred to collectively as five fingers , however, whereby

2728-472: The carpal tunnel and contribute to the deep and superficial palmar arches . Several muscle tendons attaching to the TCL and the distal carpals also contribute to maintaining the carpal arch. Compared to the carpal arches, the arch formed by the distal ends of the metacarpal bones is flexible due to the mobility of the peripheral metacarpals (thumb and little finger). As these two metacarpals approach each other,

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2816-599: The chimpanzee–human last common ancestor (CHLCA) and absent in modern humans are still present in the hands of Australopithecus , Paranthropus , and Homo floresiensis . This suggests that the derived changes in modern humans and Neanderthals did not evolve until 2.5 to 1.5 million years ago or after the appearance of the earliest Acheulian stone tools, and that these changes are associated with tool-related tasks beyond those observed in other hominins. The thumbs of Ardipithecus ramidus , an early hominin, are almost as robust as in humans, so this may be

2904-419: The dermis of palmoplantar skin inhibit melanin production and thus the ability to tan , and promote the thickening of the stratum lucidum and stratum corneum layers of the epidermis . All parts of the skin involved in grasping are covered by papillary ridges ( fingerprints ) acting as friction pads. In contrast, the hairy skin on the dorsal side is thin, soft, and pliable, so that the skin can recoil when

2992-412: The distal phalanx , the fingertip, and the surrounding soft tissues from injuries. It also serves to enhance precise delicate movements of the distal digits through counter-pressure exerted on the pulp of the finger. The nail then acts as a counter-force when the end of the finger touches an object, thereby enhancing the sensitivity of the fingertip, although the nail itself has no nerve endings. Finally,

3080-523: The ulnar nerve may result in a condition in which some of the fingers cannot be flexed. A common fracture of the hand is a scaphoid fracture —a fracture of the scaphoid bone , one of the carpal bones. This is the commonest carpal bone fracture and can be slow to heal due to a limited blood flow to the bone. There are various types of fracture to the base of the thumb; these are known as Rolando fractures , Bennet's fracture , and Gamekeeper's thumb . Another common fracture, known as Boxer's fracture ,

3168-508: The ability to use sticks to obtain termites and grubs in a manner similar to human fishing . However, not all prehensile organs are applied to tool use; the giraffe tongue, for instance, is instead used in feeding and self-cleaning . Fingernail The nail consists of the nail plate, the nail matrix and the nail bed below it, and the grooves surrounding it. The nail matrix is the active tissue (or germinal matrix ) that generates cells. The cells harden as they move outward from

3256-402: The back of the hand), the deep palmar arch , and the superficial palmar arch . Together these three arches and their anastomoses provide oxygenated blood to the palm, the fingers, and the thumb. The hand is drained by the dorsal venous network of the hand with deoxygenated blood leaving the hand via the cephalic vein and the basilic vein . The glabrous (hairless) skin on the front of

3344-404: The blood filling the capillaries of the nail bed reflects varying amounts of light incident on the nail matrix resulting in lighter shades of pink ultimately resulting in white nail beds when the hemoglobin is very low. When hemoglobin is close to 15 or 16 grams, most of the spectrum of light is absorbed and only the pink color is reflected back and the nails look pink. Essential fatty acids play

3432-453: The body, nutrient deficiencies, drug reaction or poisoning, or merely local injury. Nails can also become thickened ( onychogryphosis ), loosened ( onycholysis ), infected with fungus ( onychomycosis ), or degenerate ( onychodystrophy ). A common nail disorder is an ingrowing toenail ( onychocryptosis ). DNA profiling is a technique employed by forensic scientists on hair, fingernails, toenails, etc. The best way to care for nails

3520-418: The bones of the forearm, and a distal row ( trapezium , trapezoid , capitate and hamate ), which articulates with the bases of the five metacarpal bones of the hand. The heads of the metacarpals will each in turn articulate with the bases of the proximal phalanx of the fingers and thumb. These articulations with the fingers are the metacarpophalangeal joints known as the knuckles. At the palmar aspect of

3608-472: The claw or nail. Compared to claws, nails are flat, less curved, and do not extend far beyond the tip of the digits. The ends of the nails usually consist only of the "superficial", hardened layer and are not pointed like claws. With only a few exceptions, primates retain plesiomorphic (original, "primitive") hands with five digits, each equipped with either a nail or a claw. For example, nearly all living strepsirrhine primates have nails on all digits except

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3696-437: The densest areas of nerve endings in the body, and are the richest source of tactile feedback. They also have the greatest positioning capability of the body; thus, the sense of touch is intimately associated with hands. Like other paired organs (eyes, feet, legs) each hand is dominantly controlled by the opposing brain hemisphere , so that handedness —the preferred hand choice for single-handed activities such as writing with

3784-518: The disorders that can cause this is Catel-Manzke syndrome . The fingers may be fused in a disorder known as syndactyly . Or there may be an absence of one or more central fingers—a condition known as ectrodactyly . Additionally, some people are born without one or both hands ( amelia ). Hereditary multiple exostoses of the forearm—also known as hereditary multiple osteochondromas—is another cause of hand and forearm deformity in children and adults. There are several cutaneous conditions that can affect

3872-446: The exact number varies between people: whereas a pair of sesamoid bones are found at virtually all thumb metacarpophalangeal joints, sesamoid bones are also common at the interphalangeal joint of the thumb (72.9%) and at the metacarpophalangeal joints of the little finger (82.5%) and the index finger (48%). In rare cases, sesamoid bones have been found in all the metacarpophalangeal joints and all distal interphalangeal joints except that of

3960-996: The finger pulp and fingernail. These are usually treated by cleaning the area and applying a sterile dressing. Surgery may sometimes be required to repair the laceration or broken bones. Biotin-rich foods and supplements may help strengthen brittle fingernails. Vitamin A is an essential micronutrient for vision, reproduction, cell and tissue differentiation, and immune function. Vitamin D and calcium work together in cases of maintaining homeostasis, creating muscle contraction, transmission of nerve pulses, blood clotting, and membrane structure. A lack of vitamin A, vitamin D, or calcium can cause dryness and brittleness. Insufficient vitamin B12 can lead to excessive dryness, darkened nails, and rounded or curved nail ends. Insufficient intake of both vitamin A and B results in fragile nails with horizontal and vertical ridges. Some over-the-counter vitamin supplements such as certain multivitamins and biotin may help in growth of strong nails, although this

4048-425: The fingers and toes". The ratio of the length of the index finger to the length of the ring finger in adults is affected by the level of exposure to male sex hormones of the embryo in utero . This digit ratio is below 1 for both sexes but it is lower in males than in females on average. A number of genetic disorders affect the hand. Polydactyly is the presence of more than the usual number of fingers. One of

4136-432: The fingers are stretched. On the dorsal side, the skin can be moved across the hand up to 3 cm (1.2 in); an important input the cutaneous mechanoreceptors . The web of the hand is a "fold of skin which connects the digits". These webs, located between each set of digits, are known as skin folds (interdigital folds or plica interdigitalis). They are defined as "one of the folds of skin, or rudimentary web, between

4224-416: The first metacarpophalangeal joints are small, almost spherical bones called the sesamoid bones. The fourteen phalanges make up the fingers and thumb, and are numbered I-V (thumb to little finger) when the hand is viewed from an anatomical position (palm up). The four fingers each consist of three phalanx bones: proximal, middle, and distal. The thumb only consists of a proximal and distal phalanx. Together with

4312-406: The free edge, in that portion of the nail where the nail bed ends and can be recognized in fair-skinned people by its glassy, greyish colour. It is not visible in some individuals while it is highly prominent on others. Together, the eponychium and the cuticle form a protective seal. The cuticle is the semi-circular layer of almost invisible dead skin cells that "ride out on" and cover the back of

4400-426: The free edge, made of translucent keratin protein. Several layers of dead, compacted cells cause the nail to be strong but flexible. Its (transverse) shape is determined by the form of the underlying bone. In common usage, the word nail often refers to this part only. The nail plate is strongly attached to the nail bed and does not contain any nerves or blood vessels. The free margin ( margo liber ) or distal edge

4488-418: The groove on the dorsum of inferior side of ulna. The hand is innervated by the radial , median , and ulnar nerves . The radial nerve supplies the finger extensors and the thumb abductor , thus the muscles that extends at the wrist and metacarpophalangeal joints (knuckles); and that abducts and extends the thumb. The median nerve supplies the flexors of the wrist and digits, the abductors and opponens of

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4576-456: The hand including the nails . The autoimmune disease rheumatoid arthritis can affect the hand, particularly the joints of the fingers. Some conditions can be treated by hand surgery . These include carpal tunnel syndrome , a painful condition of the hand and fingers caused by compression of the median nerve , and Dupuytren's contracture , a condition in which fingers bend towards the palm and cannot be straightened. Similarly, injury to

4664-455: The hand of modern humans have shown that they are consistent with the stresses and requirements associated with the effective use of paleolithic stone tools. It is possible that the refinement of the bipedal posture in the earliest hominids evolved to facilitate the use of the trunk as leverage in accelerating the hand. While the human hand has unique anatomical features, including a longer thumb and fingers that can be controlled individually to

4752-447: The hand, that of the thumb is the most mobile (and the least longitudinal). While the ray formed by the little finger and its associated metacarpal bone still offers some mobility, the remaining rays are firmly rigid. The phalangeal joints of the index finger, however, offer some independence to its finger, due to the arrangement of its flexor and extension tendons. The carpal bones form two transversal rows, each forming an arch concave on

4840-400: The hand, the palm, is relatively thick and can be bent along the hand's flexure lines where the skin is tightly bound to the underlying tissue and bones. Compared to the rest of the body's skin, the hands' palms (as well as the soles of the feet ) are usually lighter—and even much lighter in dark-skinned individuals, compared to the other side of the hand. Indeed, genes specifically expressed in

4928-579: The history of recent health and physiological imbalances, and has been used as a diagnostic tool since ancient times. Deep, horizontally transverse grooves known as " Beau's lines " may form across the nails (horizontal, not along the nail from cuticle to tip). These lines are usually a natural consequence of aging, although they may result from disease. Discoloration , thinning, thickening, brittleness, splitting, grooves, Mees' lines , small white spots , receded lunula, clubbing (convex), flatness, and spooning (concave) can indicate illness in other areas of

5016-458: The human hand are plesiomorphic (shared by both ancestors and extant primate species); the elongated thumbs and short hands more closely resemble the hand proportions of Miocene apes than those of extant primates. Humans did not evolve from knuckle-walking apes, and chimpanzees and gorillas independently acquired elongated metacarpals as part of their adaptation to their modes of locomotion. Several primitive hand features most likely present in

5104-413: The human hand include: There are five digits attached to the hand, notably with a nail fixed to the end in place of the normal claw . The four fingers 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: The thumb (connected to the first metacarpal bone and trapezium )

5192-412: The human hand, including pentadactyly (having five fingers), the hairless skin of the palm and fingers, and the os centrale found in human embryos, prosimians, and apes. Furthermore, the precursors of the intrinsic muscles of the hand are present in the earliest fishes, reflecting that the hand evolved from the pectoral fin and thus is much older than the arm in evolutionary terms. The proportions of

5280-449: The index and middle finger, it forms the dynamic tridactyl configuration responsible for most grips not requiring force. The ring and little fingers are more static, a reserve ready to interact with the palm when great force is needed. The muscles acting on the hand 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

5368-420: The index finger. For example, in some individuals, the ulnar nerve supplies the entire ring finger and the ulnar side of the middle finger, whilst, in others, the median nerve supplies the entire ring finger. The hand is supplied with blood from two arteries, the ulnar artery and the radial artery . These arteries form three arches over the dorsal and palmar aspects of the hand, the dorsal carpal arch (across

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5456-479: The interlocking shapes of the carpal bones, and the wrist is therefore more stable in flexion than in extension. The distal carpal arch affects the function of the CMC joints and the hands, but not the function of the wrist or the proximal carpal arch. The ligaments that maintain the distal carpal arches are the transverse carpal ligament and the intercarpal ligaments (also oriented transversally). These ligaments also form

5544-420: The long finger. The articulations are: The fixed and mobile parts of the hand adapt to various everyday tasks by forming bony arches: longitudinal arches (the rays formed by the finger bones and their associated metacarpal bones), transverse arches (formed by the carpal bones and distal ends of the metacarpal bones), and oblique arches (between the thumb and four fingers): Of the longitudinal arches or rays of

5632-454: The motoneurons of the hand muscles; placing the hands "closer" to the brain. The recent evolution of the human hand is thus a direct result of the development of the central nervous system , and the hand, therefore, is a direct tool of our consciousness—the main source of differentiated tactile sensations—and a precise working organ enabling gestures—the expressions of our personalities. There are nevertheless several primitive features left in

5720-454: The muscle belly is located on the forearm. The intrinsic muscle groups are the thenar (thumb) and hypothenar (little finger) muscles; the interosseous muscles ( four dorsally and three volarly ) originating between the metacarpal bones; and the lumbrical muscles arising from the deep flexor (and are special because they have no bony origin) to insert on the dorsal extensor hood mechanism. The fingers have two long flexors, located on

5808-441: The nail functions as a tool enabling a so-called "extended precision grip" (e.g., pulling out a splinter in one's finger), and certain cutting or scraping actions. The growing part of the nail is under the skin at the nail's proximal end under the epidermis , which is the only living part of a nail. In mammals, the growth rate of nails is related to the length of the terminal phalanges (outermost finger bones). Thus, in humans,

5896-458: The nail of the index finger grows faster than that of the little finger; and fingernails grow up to four times faster than toenails. In humans, fingernails grow at an average rate of approx. 3.5 mm (0.14 in) a month, whereas toenails grow about half as fast (approx. average 1.6 mm (0.063 in) a month). Fingernails require three to six months to regrow completely, and toenails require twelve to eighteen months. Actual growth rate

5984-405: The nail plate rests. Nerves and blood vessels found here supply nourishment to the entire nail unit. Like all skin, it is made of two types of tissues: the dermis and the epidermis . The epidermis is attached to the dermis by tiny longitudinal "grooves" called matrix crests ( cristae matricis unguis ). In old age, the nail plate becomes thinner, and these grooves become more visible. The nail bed

6072-402: The nail root to the nail plate. The nail matrix is also known as the matrix unguis , keratogenous membrane, or onychostroma. It is the part of the nail bed that is beneath the nail and contains nerves , lymph and blood vessels . The matrix produces cells that become the nail plate. The width and thickness of the nail plate is determined by the size, length, and thickness of the matrix, while

6160-627: The nails. RDAs for iron vary considerably depending on age and gender. The recommendation for men is 8 mg per day, while that of women aged 19–50 is 18 mg per day. After women hit age 50 or go through menopause, their iron needs drop to 8 mg daily. Manicures (for the hands) and pedicures (for the feet) are health and cosmetic procedures to groom, trim, and paint the nails and manage calluses . They require various tools such as cuticle scissors , nail scissors, nail clippers , and nail files . Artificial nails can also be fixed onto real nails for cosmetic purposes. A person whose occupation

6248-403: The palmar gutter deepens. The central-most metacarpal (middle finger) is the most rigid. It and its two neighbors are tied to the carpus by the interlocking shapes of the metacarpal bones. The thumb metacarpal only articulates with the trapezium and is therefore completely independent, while the fifth metacarpal (little finger) is semi-independent with the fourth metacarpal (ring finger) which forms

6336-406: The palmar side of the thumb, index, middle, and half ring fingers. Dorsal branches innervates the distal phalanges of the index, middle, and half ring fingers. The ulnar nerve supplies the ulnar third of the hand, both at the palm and the back of the hand, and the little and half ring fingers. There is a considerable variation to this general pattern, except for the little finger and volar surface of

6424-410: The palmar side. Because the proximal arch simultaneously has to adapt to the articular surface of the radius and to the distal carpal row, it is by necessity flexible. In contrast, the capitate, the "keystone" of the distal arch, moves together with the metacarpal bones and the distal arch is therefore rigid. The stability of these arches is more dependent of the ligaments and capsules of the wrist than of

6512-415: The phalanges of the fingers and thumb these metacarpal bones form five rays or poly-articulated chains. Because supination and pronation (rotation about the axis of the forearm) are added to the two axes of movements of the wrist, the ulna and radius are sometimes considered part of the skeleton of the hand. There are numerous sesamoid bones in the hand, small ossified nodes embedded in tendons;

6600-438: The record for women is held by Diane Armstrong from Minneapolis. The nail is an unguis , meaning a keratin structure at the end of a digit. Other examples of ungues include the claw, hoof , and talon . The nails of primates and the hooves of running mammals evolved from the claws of earlier animals . In contrast to nails, claws are typically curved ventrally (downwards in animals) and compressed sideways. They serve

6688-480: The record in 1998 with a total of 20 feet 2.25 inches (615.32 cm) of nails on his left hand. His longest nail, on his thumb, was 4 feet 9.6 inches (146.3 cm) long. The former record-holder for women was Lee Redmond of the U.S., who set the record in 2001 and as of 2008 had nails with a total length on both hands of 28 feet (850 cm), with the longest nail on her right thumb at 2 feet 11 inches (89 cm). However, as of 2022,

6776-410: The second toe which is equipped with a grooming claw . Tarsiers have a grooming claw on second and third toes. Less commonly known, a grooming claw is also found on the second pedal digit of owl monkeys ( Aotus ), titis ( Callicebus ), and possibly other New World monkeys . The needle-clawed bushbaby ( Euoticus ) has keeled nails (the thumb and the first and the second toes have claws) featuring

6864-417: The shape of the fingertip bone determines if the nail plate is flat, arched, or hooked. The matrix will continue to produce cells as long as it receives nutrition and remains in a healthy condition. As new nail plate cells are made, they push older nail plate cells forward; and in this way older cells become compressed, flat, and translucent. This makes the capillaries in the nail bed below visible, resulting in

6952-412: The sides and proximal end of the nail. The lateral margin ( margo lateralis ) lies beneath the nail wall on the sides of the nail, and the nail groove or fold ( sulcus matricis unguis ) are the cutaneous slits into which the lateral margins are embedded. The paronychium is the soft tissue border around the nail, and paronychia is an infection in this area. The paronychium is the skin that overlaps onto

7040-413: The sides of the nail plate, also known as the paronychial edge. The paronychium is the site of hangnails, ingrown nails, and paronychia, a skin infection. The hyponychium is the area of epithelium, particularly the thickened portion, underlying the free edge of the nail plate. It is sometimes called the "quick", as in the phrase "cutting to the quick". A healthy fingernail has the function of protecting

7128-403: 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 first four compartments are located in the grooves present on the dorsum of inferior side of radius while the 5th compartment is in between radius and ulna. The 6th compartment is in

7216-410: The term hand in this sense to distinguish the terminations of the front paws from the hind ones is an example of anthropomorphism . The only true grasping hands appear in the mammalian order of primates . Hands must also have opposable thumbs , as described later in the text. The hand is located at the distal end of each arm. Apes and monkeys are sometimes described as having four hands, because

7304-405: 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;

7392-410: The thumb is included as one of the fingers . It has 27 bones, not including the sesamoid bone , the number of which varies among people, 14 of which are the phalanges ( proximal , intermediate and distal ) of the fingers and thumb. The metacarpal bones connect the fingers and the carpal bones of the wrist . Each human hand has five metacarpals and eight carpal bones. Fingers contain some of

7480-459: The thumb, the first and second lumbrical. The ulnar nerve supplies the remaining intrinsic muscles of the hand. All muscles of the hand are innervated by the brachial plexus (C5–T1) and can be classified by innervation: The radial nerve supplies the skin on the back of the hand from the thumb to the ring finger and the dorsal aspects of the index, middle, and half ring fingers as far as the proximal interphalangeal joints. The median nerve supplies

7568-408: The toes are long and the hallux is opposable and looks more like a thumb , thus enabling the feet to be used as hands. 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 of the bird hand and the dinosaur hand. An adult human male's hand weighs about a pound. Areas of

7656-435: 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

7744-453: The visible nail plate. The eponychium is the fold of skin cells that produces the cuticle. They are continuous, and some references view them as one entity. (Thus the names eponychium , cuticle , and perionychium would be synonymous , although a distinction is still drawn here.) It is the cuticle (nonliving part) that is removed during a manicure, but the eponychium (living part) should not be touched due to risk of infection. The eponychium

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