Nail (anatomy)

This article discusses the anatomical nails. For other uses of the term, see nail.

In anatomy, a nail is a horn-like piece at the end of an animal finger or toe. See also claw.

Fingernails and toenails, which are made of protein and are a form of modified hair, are composed of:

the nail matrix or the root of the nail - this is the growing part of the nail still under the skin at the nail's proximal end.
eponychium or cuticle which is the fold of skin at the proximal end of the nail.
paronychium which is the fold of skin on the sides of the nail.
hyponychium which is the attachment between the skin of the finger or toe and the distal end of the nail.
nail plate which is what we think of when we say nail, the hard and translucent portion, composed of keratin.
nail bed which is the adherent connective tissue that underlies the nail.
lunula which is the crescent shaped whitish area of the nail bed.

Nails grow at an average rate of 0.1 mm/day (1 cm every 100 days) . Fingernails require 3 to 6 months to regrow completely. Toenails require 12 to 18 months. Actual growth rate is dependent upon age, season, exercise level, and hereditary factors.

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 horizontal groove to form in the nails. Miscoloration, thinning, thickening, brittleness, splitting, grooves, Mee's lines, small white spots, receded lunula, clubbing(convex), flatness, spooning(convex) or can indicate illness in other areas of 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 degenerative (onychodystrophy); for further information see nail diseases.

Purpose

There are two purposes of human fingernails. Firstly, they help protect the sensitive skin underneath the nail. They also serve to help us grip and scratch. If people were to tape over their fingernails and try to carry on with their normal day, they would find it difficult, if not impossible to grip many things.

Health and Care

Nails can dry out, just like skin. They can also be infected: toe infections, for instance, can come from dirty socks, certain types of aggressive exercise, walking barefoot and exposing your feet in a moldy environment.

Manicures and pedicures are health and cosmetic procedures to groom, trim, and paint the nails and manage callouses. They require various tools such as cuticle scissors, nail scissors, nail clippers, and nail files.

Biting

Many people bite their nails. It can be habitual and is often used to relieve stress. Biting one's nails can indicate internal tension or stress.

However, biting the nails can result in the transportation of germs that are buried under the surface of the nail into the mouth. In fact, nail salons use tools that potentially affect a human in a similar way. Regarding nail tools such as files, "If they're used on different people, these tools may spread nail fungi, staph bacteria or viruses," warns Rick Lopes, 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. Thus, one can see that many pathogens have the ability to live beneath a nail, and because of this biting the nails can potentially cause health issues.

Fashion and culture

To paint the nails, nail lacquer (also known as nail polish or fingernail polish) is manually applied and allowed to dry.

In the late 20th century, artificial nails for women became widely popular. The artificial nails are not a replacement, but an extension for natural nails. There are two main approaches to creating artificial nails—tips and forms. Tips are made of lightweight plastic plates that are "nail" shaped. They are glued on the end of the natural nail and are blended into the existing natural nail using an emory board. Forms are fit over the nail and then an artificial nail is molded out of acrylic and the form is removed and then properly shaped and buffed to a shine. There are several popular techniques that can be used to create longer more perfect looking nail enhancements. One popular material is acryl—a mixture of powder and ethymethacrylate that hardens in 30–40 seconds after application. Acryl can be removed in 20 minutes using a variety of solvents. Another material, gel, hardens under ultraviolet light and can be longer lasting but more expensive. It can only be removed by cutting it off. Another popular alternative to acrylic or gel preparations are Fiberglass or Silk wraps. They are done by cutting pieces of actual fiberglass or silk fabric to fit on the surface of the nail or tip and then it is sealed down with a resin or glue. These are a possible alternative for those who are allergic to chemicals used in the acrylic or gel process. Other materials can be used, as well as combinations of them. There are also temporary, cheaper flexible tips that can be quickly glued at home without help from a professional. Acrylic nail powders are available in a variety of colours and can use "special effects" such as contours, sparkles and the very popular "French" ( pink and white appearance).

In 2003 the first ink nail printer NailJet Pro was released. It allowed individuals to print custom hi-resolution colour images on their nails. In some parts of Asia, similar but larger nail-art printers have been set up near bookstores and other popular destinations of young people. They work much like picture-taking booths.

These fashion trends are not without risks, as residues of acrylic resins have been known to lead to redness, swelling, pain and even severe allergic reactions. The nail can separate from the nail bed, and if the nail root becomes damaged, the replacement can be permanently deformed. As well, nail glue is poisonous if accidentally swallowed and most nail polishes and removers contain toxic formaldehyde or acetone.

In some Asian cultures men may also grow long fingernails, or only the nail on the little finger, to show that they do not do much manual labor, but instead work in an office setting.

Some guitar players, notably classical and fingerstyle players, will purposely grow long nails on the hand they use to pluck the strings. Their longer nails serve as small, easily-maneuverable guitar picks. Care thereof becomes a daily ritual and a mark of pride. Though this attention may seem effeminate, it is a mark of the dedication that accompanies the serious musician.

Someone whose occupation is to cut any type of nail, give artificial nails (or "nail arts") and care nails is generally called a nailist. The place where a nailist works is generally called a nailshop (or "nail shop") or a nailsalon (or "nail salon").

Shridhar Chillal holds the world record for the longest fingernails. They haven't been cut since 1958, and in 2005 they measured 7.21 metres (about 150 cm per nail). (Source: Guinness WR)

Growth after death

It is commonly claimed that nails and hair will continue growing for several days after death. This is a myth; the appearance of growth is actually caused by the retraction of skin as the surrounding tissue dehydrates (desiccation), making nails and hair more prominent.

References

American Academy of Dermatology - Nail Health
ImagiNail Website
Digi Nail Art Website
Tram Kim Nguyen, "The Truth About Germs", Fitness Magazine. Accessed 10 April 2005.
Judith Cobb, Fingernails, Jewels or Tools? Nature's Field - Nail diagnosis]
Scratching the surface of fingernails.

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Integumentary system | Nails