Nail (anatomy)
From Wikipedia, the free encyclopedia
- 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.
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[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 composed of:
- The Free Edge is the part of the nail the extends past the finger, beyond the nail plate. There are no nerve endings, thus it does not hurt to cut it.
- 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.
- 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 0.1 mm/day (1 cm every 100 days) . 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. 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.
[edit] Biting
Many people bite their nails. It often indicates internal tension, stress, boredom, hunger, or it may simply be a habit.
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.
[edit] Fashion and 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.
To paint the nails, nail lacquer (also known as nail polish or fingernail polish) is manually applied and allowed to dry. Typical colours for women are red, pink, clear, and "natural" (an off-white intended to match the color of an undecorated nail).
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 under 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 commonly called "acrylics" is a mixture of a polymer powder and a liquid monomer (e.g.ethylmethacrylate). The mixture starts to harden in 30–40 seconds after application and continues to cure to final hardness typically for more than an hour. Powder and liquid acrylics can be removed in 20 minutes using a variety of solvents (usually acetone is used). Another material, commonly called "UV gel", (in correct chemical terms a polymer resin) hardens under ultraviolet light. Depending on brand these can show a broader variety of quality and properties (flexibility, stength, etc.) but may be but more expensive. They generally cannot be removed by organic solvents, but only be removed by filing (or left to grow out with the natural nail). 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. 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.
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). Care thereof becomes a daily ritual and a mark of pride. Though this attention may seem vain, 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").
In some West European cultures (mainly Portugal) youth grow their little finger and thumb fingernails long, both male and female alike.
[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.
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] Myth
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.
[edit] See also
[edit] References
| Wikimedia Commons has media related to: |
- Fingernails
- Haneke E (2006). "Surgical anatomy of the nail apparatus.". Dermatol Clin 24 (3): 291-6. PMID 16798426.
- ↑ American Academy of Dermatology - Nail Health
- ↑ ImagiNail Website
- ↑ Creative Nail Design Website
- ↑ en Vogue Sculptured Nails Inc. 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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