Nail (anatomy)

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

Anatomy

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

1 Parts of the fingernail
2 Growth
3 Health and care
4 Biting
5 Culture
6 Fashion
7 Medical test
8 Myths
9 See also
10 References

[edit] Parts of the fingernail

Fingernails and toenails, which are made of a tough protein called keratin and are a form of modified hair, are made up of many different parts:

The free edge is the part of the nail the extends past the finger, beyond the nail plate. There are no nerve endings in the nail - this is the growing part of the nail still under the skin at the nail's proximal end.
eponychium or cuticle, is the fold of skin at the proximal end of the nail.
paronychium is the fold of skin on the sides of the nail.
hyponychium is the attachment between the skin of the finger or toe and the distal end of the nail.
nail plate is what we think of when we say nail, the hard and translucent portion, composed of keratin.
nail bed is the adherent connective tissue that underlies the nail.
lunula is the crescent shaped whitish area of the nail bed (when visible)
nail fold a fold of hard skin overlapping the base and sides of a fingernail or toenail.

[edit] Growth

Nails grow at an average rate of 0.1mm a day (1 cm every 100 days) ^[1]. Fingernails require 4 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.^[2] 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 (concave) 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.

[edit] 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 as well as walking unprotected in an unclean 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.

However, nail salons use tools that potentially infect people. 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.^[3] In fact, over 100 bacterial skin infections in 2000 were traced to footbaths in nail salons.

[edit] Biting

Main article: Nail biting

Many people bite their nails. It often indicates internal tension, stress, boredom, hunger, or it may simply be a habit.

Biting the nails can result in the transportation of germs that are buried under the surface of the nail into the mouth.

Biting may also result in excessive or abnormal wear of tooth enamel.

The Ci-Xi Imperial Empress Dowager displays long fingernails which reflect her high position in Qing China.

[edit] Culture

In western culture, long nails are a symbol of femininity, while short nails are a symbol of masculinity. Nail decoration is usually limited to females.

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. However, this practice is gradually becoming unpopular and unrefined because a long fingernail on the little finger is variously associated with either nose picking or cocaine usage.

In the 19th century in the Balkans, white-collar workers, such as clerks, grew their fingernails long to distiguish them from people in lower classes who worked with their hands. ^[1]

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 (use of acrylic or "gel" nail enhancements is also growing in popularity, because the natural nail sometimes wears off faster by playing than it can grow back). For some serious musicians, daily nail care can become a mark of pride and dedication.

In comparison, pianists must keep their nails trimmed short to avoid clicking noises on the keys, and most string players, such as violinists and guitarists, must keep at least the nails on their string hand short to allow the strings to be fingered correctly.

[edit] Fashion

Main article: Manicure

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

Painting the nails with nail polish (also known as nail lacquer) is a common practice dating back to at least 3000 B.C.

[edit] Medical test

Health care and pre-hospital care providers (paramedics) often use the fingernail beds as a cursory indicator of distal tissue perfusion of individuals who may be in shock. However, this test is now accepted as reliable in young children only.

Procedure: Gently depress and release the fingernail bed with your finger. This act will briefly turn your nailbed white and normally return to a pink colour within 1-2 seconds. Delayed return to pink colour could be an indicator of certain shock states such as hypovolemia.

[edit] Myths

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

It is a myth that some cosmetic products can give strong, thick nails. Nail cells are formed in the matrix, and as they push out onto the nail plate they turn 90 degrees and flatten out; hence, the length of the nail matrix determines the natural thickness of the nail. If the matrix is long, naturally thick nails will grow long and strong with proper care. With a short matrix, thin nails will always grow thin and no cosmetic product will ever change that.