A
nail is a
hornA horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...
-like structure at the end of a person's (or an animal's)
fingerA 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...
or
toeToes are the digits of the foot of an animal. 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 plantigrade; unguligrade animals are those that walk on hooves at the tips of...
. See also
clawA 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...
.
Parts of the nail
Fingernails and
toenails are made of a tough
proteinProteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues...
called
keratinKeratins are a family of fibrous structural proteins; tough and insoluble, they form the hard but un-mineralized structures found in reptiles, birds, amphibians, and mammals...
, as are animals' hooves and horns. Along with hair and teeth they are an appendage of the skin. The parts of the nail are:
- Matrix
In biology, matrix is the material between animal or plant cells, the material in which more specialized structures are embedded, and a specific part of the mitochondrion that is the site of oxidation of organic molecules. The internal structure of connective tissues is an extracellular matrix...
- The only living part of the nail. It is situated behind and underneath the nail fold and produces the keratin which makes up the nail plate. If the matrix is damaged, growth of the nail plate is affected.
- Eponychium
In human anatomy, the eponychium [Greek epi + onychion ], also known as the cuticle is the thickened layer of skin surrounding fingernails and toenails. Beneath the cuticle is a thin layer of a membrane known as the pterygium. The function is to protect the area between the nail and epidermis from...
- Dead skin that forms around 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. Cuticles are non-homologous, differing in their origin, structure and chemical composition.-Human anatomy:In human anatomy, cuticle ...
area. It can be lifted and trimmed during a professional manicure treatment. Tends to be more prominent on males.
- Paronychium
Paronychium or the "lateral nail fold" is the term for the soft tissue surrounding the border of the fingernail or toenail. -Clinical significance:...
- The 'live' skin that folds around the cuticle area, giving protection to the matrix
- Hyponychium
- The area of attachment between the nail plate and nail bed that lies underneath the free edge. Anatomical terms of location: proximal and distal, end of the nail.
- Nail plate
The nail plate is the hard and translucent portion of the nail, composed of keratin....
- The hard and translucent part of the nail composed of layers of keratin
- Nail bed
Nail bed can refer to:* Bed of nails, a device sometimes used in meditation and physics demonstrations* Bed of nails tester, a device used to test printed circuit boards* Fingernail region also known as the "quick"...
- Tissue underneath the nail plate, responsible for the pink colour of the nail. It also determines what shape the nail will grow.
- Lunula
The lunula, or lunulae , is the crescent-shaped whitish area of the bed of a fingernail or toenail. The lunula is the visible part of the nail matrix The lunula, or lunulae (pl.) (nail moon), is the crescent-shaped whitish area of the bed of a fingernail or toenail. The lunula is the visible part...
- The visible part of the matrix, a whitish crescent shape around the base of the nail plate. Tends to only be visible in larger nails.
- Nail fold
- A fold of hard skin overlapping the base and sides of a fingernail or toenail
- Free edge
- The part of the nail that extends past the finger, beyond the nail plate. There should always be a free edge present to prevent infections. Ideally a free edge should be half of the 'pink' nail in length.
- Nail groove
- Grooves that guide the direction of nail growth. They are located down the sides of the nail fold.
The only living part of a nail is located inside or underneath the epidermis.
Nails act as a counterforce when the end of the finger touches an object, thereby enhancing the sensitivity of the fingertip, even though there are no nerve endings in the nail itself. The growing part of the nail is the part still under the skin at the nail's proximal end. The average thickness of this portion of the nail is .016 inches, or 0.43 millimetres.
In common usage, the word
nail often refers to the nail plate only.
Growth
Nails grow at an average rate of 3 millimeters (1/8 inch) a month. Fingernails require 3 to 6 months to regrow completely, and toenails require 12 to 18 months. Actual growth rate is dependent upon age, gender, season, exercise level, diet, and hereditary factors. Nails grow faster in the summer than in any other season. 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.
This growth record can show the history of recent health and physiological imbalances, and has been used as a diagnostic tool since ancient times. Major illness will cause a
deep transverse grooveBeau's lines are deep grooved lines that run from side to side on the fingernail. They may look like indentations or ridges in the nail plate. This condition of the nail was named by a French physician, Joseph Honoré Simon Beau , who first described it in 1846.Beau's lines are horizontal, going...
to form across the nails (not along the nail from
cuticleA 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. Cuticles are non-homologous, differing in their origin, structure and chemical composition.-Human anatomy:In human anatomy, cuticle ...
to tip). Discoloration, thinning, thickening, brittleness, splitting, grooves,
Mees' linesMees' lines or Aldrich-Mees' lines are lines of discoloration across the nails of the fingers and toes.- Causes :Mees' lines appear after an episode of poisoning with arsenic, thallium or other heavy metals, and can also appear if the subject is suffering from renal failure.- Presentation :They are...
,
small white spotsLeukonychia is a medical term for white discoloration appearing on nails. It is derived from the Greek words Leuko white and Onyx nail. The most common cause is injury to the base of the nail where the nail is formed.-Leukonychia Totalis:This condition is a whitening of the entire nail...
, receded lunula,
clubbingIn medicine, clubbing is a deformity of the fingers and fingernails that is associated with a number of diseases, mostly of the heart and lungs. Idiopathic clubbing can also occur...
(convex), flatness, spooning (concave) can indicate illness in other areas of the body, nutrient deficiencies, drug reaction or
poisonIn the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism...
ing, or merely local injury. Nails can also become thickened (
onychogryphosisOnychogryphosis is a hypertrophy thembling claws or a ram's horn, possibly caused by trauma or peripheral vascular disorders, but most often secondary to neglect and failure to cut the nails for extended periods of time...
), loosened (
onycholysisOnycholysis refers to the detachment of the nail from the nail bed, starting at its distal and/or lateral attachment. It is said to occur particularly on the ring finger but can occur on any of the fingernails. It can occur in thyrotoxicosis and is thought to be due to sympathetic overactivity....
), infected with fungus (
onychomycosis Onychomycosis means fungal infection of the nail. It is the most common disease of the nails and constitutes about a half of all nail abnormalities....
) or degenerate (onychodystrophy); for further information see
nail diseaseNail diseases are distinct from diseases of the skin. Although nails are a skin appendage, they have their own signs and symptoms which may relate to other medical conditions. Nail conditions that show signs of infection or inflammation require medical assistance and cannot be treated at a beauty...
s.
Health and care
Nails can dry out, just like
skinThe skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system made up of multiple layers of mesodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, birds...
. They can also peel, break and be infected. Toe infections, for instance, can be caused or exacerbated by dirty
sockSocks or sox are a knitted or woven type of hosiery for enclosing the human feet. Socks are designed to:* ease chafing between the foot and footwear* protect footwear by absorbing perspiration and dead skin lost from the foot* provide comfort...
s, specific types of aggressive exercise, tight
footwearFootwear consists of garments worn on the feet, for protection against the environment, and adornment. Socks and other hosiery are usually worn between the feet and the footwear, less often with sandals and flip flops...
, and walking unprotected in an unclean environment.
ManicureA manicure is a cosmetic beauty treatment for the fingernails and hands performed either at home or in a nail salon by a licensed professional nail technician or manicurist. A manicure treatment is not only a treatment for the natural nails but also for the hands...
s and
pedicureA pedicure is a way to improve the appearance of the feet and their nails. It provides a similar service to a manicure. The word pedicure comes from the Latin words pedis, which means of the foot, and cura, which means care. It also means the care of the feet and toenails. A pedicure can help...
s 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 clipperA nail clipper is a mechanical device used to trim fingernails and toenails.-Design:Nail clippers are usually made of metal. Two common varieties are the plier type and the lever type. Both are common household objects. Most nail clippers usually come with another tool attached, which is used to...
s, and
nail fileA 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...
s.
Artificial nailsArtificial nails, also known as fake nails, fashion nails, nail enhancements, or nail extensions, are coverings placed over fingernails as fashion accessories. Some artificial nails attempt to mimic the look of real fingernails as closely as possible, while other designs may deliberately stray in...
can also be appended onto real nails for cosmetic purposes.
Nail tools used by different people may transmit infections. Regarding nail tools such as files, "If they're used on different people, these tools may spread nail fungi, staph bacteria or viruses," warns Ted Dischman, a spokesperson for the California Board of Barbering and Cosmetology. In fact, over 100 bacterial skin infections in 2000 were traced to footbaths in nail salons. To avoid this, new improved contactless tools can be used, for example, gel and cream cuticle removers instead of cuticle scissors.
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 clipperA nail clipper is a mechanical device used to trim fingernails and toenails.-Design:Nail clippers are usually made of metal. Two common varieties are the plier type and the lever type. Both are common household objects. Most nail clippers usually come with another tool attached, which is used to...
.
Fashion
A person whose occupation is to cut any type of nail, apply artificial nails, and care for nails is sometimes called a
nail technician. The place where a nail technician works may be a nail salon or nail shop (also
nailshop).
Painting the nails with
nail polishNail polish is a lacquer applied to toenails or fingernails for appearance, but also as nail protection. Polishing afterward without adding another chemical layer is called nail buffing.-History:...
(also called
nail lacquer and
nail varnish) is a common practice dating back to at least 3000 B.C.
Ornamented fake nails are sometimes used to display designs, such as stars or sparkles, on nails. They are also used to make nails look longer.
People sometimes grow a habit of biting or attacking their nails, making them short and uneven. Because longer nails are considered more fashionable, some people try various methods of breaking this habit, such as applying bitter varnish to their nails/nail polish, or making New Year's resolutions to stop biting them.
Medical test
Healthcare and pre-hospital-care providers (EMTs or paramedics) often use the fingernail beds as a cursory indicator of distal tissue perfusion of individuals that may be
dehydratedDehydration is defined as excessive loss of body water. It is literally the removal of water from an object. In physiological terms, it entails a relative deficiency of water molecules in relation to other dissolved solutes...
or in shock. However, this test is not considered reliable in adults. This is known as the
CRT or blanch testCapillary refill is the rate at which blood refills empty capillaries. It can be measured by holding a hand higher than heart-level , pressing a fingernail until it turns white, and taking note of the time needed for colour to return once the nail is released. Normal refill time is less than 2...
.
WEJ Procedure: briefly depress the fingernail bed gently with a finger. This will briefly turn the nailbed white; the normal pink colour should be restored within a second or two. Delayed return to pink colour can be an indicator of certain shock states such as
hypovolemiaIn physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
See also
- Hangnail
A hangnail or agnail is a small, torn piece of skin near a fingernail or toenail. Unlike whitlows, hangnails are usually caused by dry skin or nail biting, and may be prevented with proper moisturization of the skin....
- Leukonychia
Leukonychia is a medical term for white discoloration appearing on nails. It is derived from the Greek words Leuko white and Onyx nail. The most common cause is injury to the base of the nail where the nail is formed.-Leukonychia Totalis:This condition is a whitening of the entire nail...
- Lunula
The lunula, or lunulae , is the crescent-shaped whitish area of the bed of a fingernail or toenail. The lunula is the visible part of the nail matrix The lunula, or lunulae (pl.) (nail moon), is the crescent-shaped whitish area of the bed of a fingernail or toenail. The lunula is the visible part...
- Nail biting
Onychophagia or nail biting is a common oral compulsive habit in children and adults, affecting around 30% of children between 7 to 10 years and 45% of teenagers.-Negative effects:...
- Nail disease
Nail diseases are distinct from diseases of the skin. Although nails are a skin appendage, they have their own signs and symptoms which may relate to other medical conditions. Nail conditions that show signs of infection or inflammation require medical assistance and cannot be treated at a beauty...
- Periungual wart