A nail is a claw-like plate found at the tip of the
fingers
A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers ( Pentadactyly). Chambers ...
and
toes
Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plant ...
on most
primate
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...
s. Nails correspond to the
claw
A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...
s found in other animals. Fingernails and toenails are made of a tough protective
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
called
alpha-keratin
Alpha-keratin, or α-keratin, is a type of keratin found in vertebrates. This protein is the primary component in hairs, horns, mammalian claws, nails and the epidermis layer of the skin. α-keratin is a fibrous structural protein, meaning it is ...
, which is a
polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
. Alpha-keratin is found in the hooves, claws, and horns of
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s.
Structure
![Human nail anatomy](https://upload.wikimedia.org/wikipedia/commons/1/11/Human_nail_anatomy.jpg)
The nail consists of the nail plate, the nail matrix and the nail bed below it, and the grooves surrounding it.
Parts of the nail
The matrix, sometimes called the ''matrix unguis'', keratogenous membrane, nail matrix, or onychostroma, is the active
tissue (or
germinal matrix
Matrix most commonly refers to:
* ''The Matrix'' (franchise), an American media franchise
** ''The Matrix'', a 1999 science-fiction action film
** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...
) that generates cells, which harden as they move outward from the nail root to the nail plate.
It is the part of the nail bed that is beneath the nail and contains
nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
s,
lymph
Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to ...
and
blood vessel
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
s.
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 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 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 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
The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...
and the
epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
. 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 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 the free edge, made of translucent
keratin
Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
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 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
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
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 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.
Eponychium
Together, the
eponychium
In human anatomy, the eponychium is the thickened layer of skin at the base of the fingernails and toenails. It can also be called the medial or proximal nail fold. The eponychium differs from the cuticle; the eponychium comprises live skin cells ...
and the
cuticle
A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
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 the visible nail plate while the eponychium is the fold of skin cells that produces the cuticle. They are continuous, and some references view them as one entity; in this classification, the names ''eponychium'', ''cuticle'', and ''perionychium'' are
synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
ous.
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
In human anatomy, the eponychium is the thickened layer of skin at the base of the fingernails and toenails. It can also be called the medial or proximal nail fold. The eponychium differs from the cuticle; the eponychium comprises live skin cells ...
is a small band of living cells (
epithelium
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
) that extends from the posterior nail wall onto the base of the nail.
The
eponychium
In human anatomy, the eponychium is the thickened layer of skin at the base of the fingernails and toenails. It can also be called the medial or proximal nail fold. The eponychium differs from the cuticle; the eponychium comprises live skin cells ...
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 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.
Paronychium
The paronychium is the soft tissue border around the nail,
and
paronychia
Paronychia is an inflammation of the skin around the nail, which can occur suddenly, when it is usually due to the bacterium '' Staphylococcus aureus'', or gradually when it is commonly caused by the fungus ''Candida albicans''. The term is fr ...
is an infection in this area.
The paronychium is the skin that overlaps onto 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.
Hyponychium
The
hyponychium
The hyponychium is the area of epithelium, particularly the thickened portion, underlying the free edge of the nail plate on the nail. Its proximal border is immediately distal to distal limit of nail bed—a.k.a. the onychodermal band (the line ...
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".
Function
A healthy fingernail has the function of protecting the
distal phalanx
The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...
, 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, 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.
Growth
The growing part of the nail is under the skin at the nail's
proximal
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
end under the
epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
, 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
The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones.
...
(outermost finger bones). Thus, in humans, the nail of the
index finger
The index finger (also referred to as forefinger, first finger, second finger, pointer finger, trigger finger, digitus secundus, digitus II, and many other terms) is the second digit of a human hand. It is located between the thumb and the mid ...
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. a month, whereas toenails grow about half as quickly (approx. average a month). Fingernails require three to six months to regrow completely, and toenails require twelve to eighteen months. Actual growth rate is dependent upon age, sex, season, exercise level, diet, and
hereditary
Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic inform ...
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
Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals.
The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and f ...
) appear to grow.
Permeability
The nail is often considered an impermeable barrier, but this is not true. In fact, it is much more permeable than the skin,
[K. A. Walters and G. L. Flynn, Permeability characteristics of the human nail plate, International Journal of Cosmetic Science 5, 231–46 (1983)]
/ref> 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
Paraquat (trivial name; ), or ''N'',''N''′-dimethyl-4,4′-bipyridinium dichloride (systematic name), also known as methyl viologen, is an organic compound with the chemical formula C6H7N)2l2. It is classified as a viologen, a family of redox ...
, a fast acting herbicide
Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
that is harmful to humans, urea
Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid.
Urea serves an important r ...
which is often an ingredient in creams and lotions meant for use on hands and fingers, and several fungicidal agents such as salicylic acid
Salicylic acid is an organic compound with the formula HOC6H4CO2H. A colorless, bitter-tasting solid, it is a precursor to and a metabolite of aspirin (acetylsalicylic acid). It is a plant hormone, and has been listed by the EPA Toxic Substance ...
, miconazole
Miconazole, sold under the brand name Monistat among others, is an antifungal medication used to treat ring worm, pityriasis versicolor, and yeast infections of the skin or vagina. It is used for ring worm of the body, groin (jock itch), and fee ...
branded Monistat, natamycin
Natamycin, also known as pimaricin, is an antifungal medication used to treat fungal infections around the eye. This includes infections of the eyelids, conjunctiva, and cornea. It is used as eyedrops. Natamycin is also used in the food industr ...
; and sodium hypochlorite
Sodium hypochlorite (commonly known in a dilute solution as bleach) is an Inorganic chemistry, inorganic chemical compound with the chemical formula, formula NaOCl (or NaClO), comprising a sodium cation () and a hypochlorite anion (or ). It may ...
which is the active ingredient in common household bleach (but usually only in 2–3% concentration).[
]
Clinical significance
Healthcare and pre-hospital-care providers ( EMTs or paramedic
A paramedic is a registered healthcare professional who works autonomously across a range of health and care settings and may specialise in clinical practice, as well as in education, leadership, and research.
Not all ambulance personnel are p ...
s) often use the fingernail beds as a cursory indicator of distal tissue perfusion
Perfusion is the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue, usually referring to the delivery of blood to a capillary bed in tissue. Perfusion is measured as the rate at which blood is deliver ...
of individuals who may be dehydrated
In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
or in shock
Shock may refer to:
Common uses Collective noun
*Shock, a historic commercial term for a group of 60, see English numerals#Special names
* Stook, or shock of grain, stacked sheaves
Healthcare
* Shock (circulatory), circulatory medical emergen ...
. 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
Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. This may be due to either a loss of both salt and water or a decrease in blood volume. Hypovolemia refers to the los ...
.
Nail growth record can show the history of recent health and physiological imbalances, and has been used as a diagnostic tool
Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...
since ancient times. Deep, horizontally transverse grooves known as "Beau's lines
Beau's lines are deep grooved lines that run from side to side on the fingernail or the toenail. They may look like indentations or ridges in the nail plate.Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McG ...
" 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
Mees' lines or Aldrich–Mees lines, also called leukonychia striata, are white lines of discoloration across the nails of the fingers and toes (leukonychia).
Presentation
They are typically white bands traversing the width of the nail. As the ...
, small white spots, receded lunula, clubbing (convex), flatness, and spooning (concave) can indicate illness in other areas of the body, nutrient
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
deficiencies, drug reaction or poisoning, or merely local injury.
Nails can also become thickened (onychogryphosis
Onychogryphosis is a hypertrophy that may produce nails resembling claws or a ram's horn.
Causes
Onychogryphosis may be caused by trauma or peripheral vascular disease, but most often secondary to self-neglect and failure to cut the nails for ...
), loosened (onycholysis
Onycholysis is a common medical condition characterized by the painless detachment of the nail from the nail bed, usually starting at the tip and/or sides. On the hands, it occurs particularly on the ring finger but can occur on any of the fingern ...
), infected with fungus
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
(onychomycosis
Onychomycosis, also known as tinea unguium, is a fungal infection of the nail. Symptoms may include white or yellow nail discoloration, thickening of the nail, and separation of the nail from the nail bed. Toenails or fingernails may be affected ...
), or degenerate
Degeneracy, degenerate, or degeneration may refer to:
Arts and entertainment
* Degenerate (album), ''Degenerate'' (album), a 2010 album by the British band Trigger the Bloodshed
* Degenerate art, a term adopted in the 1920s by the Nazi Party i ...
(onychodystrophy
A nail is a claw-like plate found at the tip of the fingers and toes on most primates. Nails correspond to the claws found in other animals. Fingernails and toenails are made of a tough protective protein called alpha-keratin, which is a polymer. ...
). A common nail disorder is an ingrowing toenail (onychocryptosis
An ingrown nail, also known as onychocryptosis from el, ὄνυξ () 'nail' and () 'hidden', is a common form of nail disease. It is an often painful condition in which the nail (anatomy), nail grows so that it cuts into one or both sides of ...
).
DNA profiling
DNA profiling (also called DNA fingerprinting) is the process of determining an individual's DNA characteristics. DNA analysis intended to identify a species, rather than an individual, is called DNA barcoding.
DNA profiling is a forensic tec ...
is a technique employed by forensic scientists
Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal ...
on hair, fingernails, toenails, etc.
Health and care
The best way to care for nails 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
Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
.
Bluish or purple fingernail beds may be a symptom of peripheral cyanosis
Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Body tissues that show cyanosis are usually in locations ...
, which indicates oxygen deprivation.
Nails can dry out, just like skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
. They can also peel, break, and be infected. Toe infections, for instance, can be caused or exacerbated by dirty
Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty.
Common types of dirt include:
* Debris: scattered pieces of waste or remains
* Dust: a genera ...
sock
A sock is a piece of clothing worn on the feet and often covering the ankle or some part of the calf. Some types of shoes or boots are typically worn over socks. In ancient times, socks were made from leather or matted animal hair. In the late ...
s, specific types of aggressive exercise
Exercise is a body activity that enhances or maintains physical fitness and overall health and wellness.
It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic ...
(long-distance running
Long-distance running, or endurance running, is a form of continuous running over distances of at least . Physiologically, it is largely aerobic in nature and requires stamina as well as mental strength.
Within endurance running comes two d ...
), tight footwear
Footwear refers to garments worn on the feet, which typically serves the purpose of protection against adversities of the environment such as wear from ground textures and temperature. Footwear in the manner of shoes therefore primarily serves th ...
, and walking unprotected in an unclean environment
Environment most often refers to:
__NOTOC__
* Natural environment, all living and non-living things occurring naturally
* Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
. Common organisms causing nail infections include yeasts
Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...
and molds (particularly dermatophytes
Dermatophyte (from Greek '' derma'' "skin" (GEN ''dermatos'') and ''phyton'' "plant") is a common label for a group of fungus of ''Arthrodermataceae'' that commonly causes skin disease in animals and humans. Traditionally, these anamorphic (as ...
).
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 a dermatologist
Dermatology is the branch of medicine dealing with the skin.''Random House Webster's Unabridged Dictionary.'' Random House, Inc. 2001. Page 537. . It is a speciality with both medical and surgical aspects. A dermatologist is a specialist medical ...
with a focus in this particular area of medicine. However, most times it is a nail technician 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
A nail clipper (also called nail clippers, a nail trimmer, a nail cutter or nipper type) is a hand tool used to trim fingernails, toenails and hangnails.
Design
Nail clippers are usually made of stainless steel but can also be made of plastic an ...
.
Effect of nutrition
Biotin-rich foods and supplements may help strengthen brittle fingernails. A few small studies support biotin supplement use to that effect. One study in 35 people with brittle fingernails found that 2.5 mg of biotin per day for six weeks to seven months improved symptoms in 63% of participants.
Vitamin A
Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably bet ...
is an essential micronutrient for vision, reproduction, cell and tissue differentiation, and immune function. Vitamin D
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 (c ...
and calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
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
Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, in both fatty acid and amino acid metabolism. It ...
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 multivitamin
A multivitamin is a preparation intended to serve as a dietary supplement with vitamins, dietary minerals, and other nutritional elements. Such preparations are available in the form of tablets, capsules, pastilles, powders, liquids, or injectable ...
s and biotin
Biotin (or vitamin B7) is one of the B vitamins. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids. The name ''biotin'', bor ...
may help in growth of strong nails, although this 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 your nails.
Omega-3 fatty acids can help lubricate and moisturize your nails, giving them a shiny appearance. These fatty acids may also reduce inflammation in your nail bed, which nourishes and promotes the health of cells that give rise to your nail plate. A lack of omega-3 fatty acids could contribute to dry and brittle nails.
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
is a building material for new nails; therefore, low dietary protein intake may cause anemia and the resultant reduced hemoglobin in 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
Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them.
Only two fatty acids are known to be essential for humans: alpha-linolenic ac ...
play a large role in healthy skin as well as nails. Splitting and flaking of nails may be due to a lack of linoleic acid
Linoleic acid (LA) is an organic compound with the formula COOH(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are cis-trans isomerism, ''cis''. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 ''cis''-9,12. A linoleate is a salt (chem ...
.
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 in your nails or your nails may concave or “spoon”. 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.
Society and culture
Fashion
Manicures (for the hands) and pedicures (for the feet) are health and cosmetic procedures to groom, trim, and paint the nails and manage callus
A callus is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, but they may o ...
es. They require various tools such as cuticle scissors
Scissors are hand-operated shearing tools. A pair of scissors consists of a pair of metal blades pivoted so that the sharpened edges slide against each other when the handles (bows) opposite to the pivot are closed. Scissors are used for cutti ...
, nail scissors, nail clipper
A nail clipper (also called nail clippers, a nail trimmer, a nail cutter or nipper type) is a hand tool used to trim fingernails, toenails and hangnails.
Design
Nail clippers are usually made of stainless steel but can also be made of plastic an ...
s, and nail file
A nail file is a tool used to gently grind down and shape the edges of nails. They are often used in manicures and pedicures after the nail has been trimmed using appropriate nail clippers. Nail files may either be emery boards, ceramic, glass, c ...
s. Artificial nails
Artificial nails, also known as fake nails, false nails, acrylic nails, nail extensions or nail enhancements, are extensions placed over fingernails as fashion accessories. Many artificial nail designs attempt to mimic the appearance of real fi ...
can also be fixed onto real nails for cosmetic purposes.
A person whose occupation 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 technician
A manicurist or nail technician is a person whose occupation is to style and shape a person's nails. This is achieved using a combination of decorating nails with coloured varnish, transfers, gems or glitter.
Basic treatments include manicures a ...
. The place where a nail technician works may be a nail salon
A nail salon or nail bar is a specialty beauty salon establishment that primarily offers nail care services such as manicures, pedicures, and nail enhancements. Often, nail salons also offer skin care services. Manicures are also offered by gene ...
or nail shop or nail bar.
Acrylic nails are made out of acrylic glass (PMMA). When it 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.
Painting the nails with colored nail polish
Nail polish (also known as nail varnish or nail enamel) is a lacquer that can be applied to the human fingernail or toenails to decorate and protect the nail plates. The formula has been revised repeatedly to enhance its decorative properties ...
(also called nail lacquer and nail varnish) to improve the appearance is a common practice dating back to at least 3000 B.C. With the rise of smartphones, some analysts have noted a trend of the '' nelfie'' (nail selfie), wherein people share their nail art online.
Gel nails can be utilized 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 a high-gloss finish and last for two to three weeks.
Nail wraps are formed by cutting pieces of fiberglass
Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth ...
, 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 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 is to drill, clip off, or buff out layers of the powder so, when they are soaking in acetone, they slide right off.
Length records
''Guinness World Records
''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...
'' began tracking record fingernail lengths in 1955, when a Chinese priest was listed as having fingernails long.
The current record-holder for men, according to ''Guinness'', is Shridhar Chillal
Shridhar Chillal (born 29 January 1937) is an Indian people, Indian man from the city of Pune, who held the world record for the longest nail (anatomy), fingernails ever reached on a single hand, with a combined length of 909.6 centimeters (358. ...
from India who set the record in 1998 with a total of of nails on his left hand. His longest nail, on his thumb, was long.
The record-holder for women is Lee Redmond
Lee Redmond (born February 2, 1941) is an American woman who held the record in the ''Guinness World Records'' for longest fingernails on both hands.
''Guinness World Records''
The '' Enquirer'' featured her every few years and kept track of ...
of the U.S., who set the record in 2001 and as of 2008 had nails with a total length on both hands of , with the longest nail on her right thumb at .
Evolution in primates
The nail is an ''unguis
A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...
'', meaning a keratin structure at the end of a digit. Other examples of ''ungues'' include the claw, hoof
The hoof (plural: hooves) is the tip of a toe of an ungulate mammal, which is covered and strengthened with a thick and horny keratin covering. Artiodactyls are even-toed ungulates, species whose feet have an even number of digits, yet the rumin ...
, and talon
Talon or talons may refer to:
Science and technology
* Talon (anatomy), the claw of a bird of prey
* Brodifacoum, a rodenticide, also known as the brand Talon
* TALON (database), a database maintained by the US Air Force
* Talon, an anti-vehicle- ...
. The nails of primate
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...
s and the hooves of running mammals evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation t ...
from the claws of synapsid, earlier animals.[
]
In contrast to nails, claws are typically curved ventrally (downwards in animals) and compressed sideways. They serve a multitude of functionsincluding climbing, digging, and fightingand have undergone numerous adaptive changes in different animal Taxon, 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 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 Strepsirrhini, strepsirrhine primates have nails on all digits except 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 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:
# expanded apical pads (fingertips),
# developed epidermal ridges (fingerprints),
# broadened distal parts of distal phalanges (fingertip bones), and
# reduced flexor and extensor tubercles (attachment areas for finger muscles on bones).
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) is a derived postural adaptation rather than retained ancestral condition.[
]
See also
*List of cutaneous conditions
*Nail disease
*Nail fetish (disambiguation), Nail fetish
*Onychogryphosis, overgrown, claw-like nails
References
External links
*
{{DEFAULTSORT:Nail (Anatomy)
Nails (anatomy),