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(anatomy) The horny epidermal derivative covering the dorsal aspect of the terminal phalanx of each finger and toe.
(design engineering) A slender, usually pointed fastener with a head, designed for insertion by impact.
(engineering) To drive nails in a manner that will position and hold two or more members, usually of wood, in a desired relationship.
(medicine) A metallic rod with one blunt end and one sharp end, used surgically to anchor bone fragments.

The replacement of sharp claws with flattened nails in primates is considered part of the evolutionary development of a hand able to grasp objects. The nails start to develop in the fetus by the end of the third month, and are formed from the same epidermal tissue as the skin. They reach the ends of the fingers and toes about a month before birth.

The mature nail is a plate of the protein keratin which is also present in hair and skin. The pale ‘half-moon’ at the base — often exposed above the nail-fold only on the thumbs and big toes — marks the area of the bed of the nail where its substance is formed and from which it grows — the germinal matrix. The rest of the nail bed provides a surface for the growing nail to slide over as it advances at the rate of about 0.1 mm/day. The germinal cells continually divide to replace those which generate, and disappear into the non-cellular substance of the nail. This proliferation can be interrupted by injuries or acute illnesses, leaving grooves across the nails which gradually grow out.

The decoration of both toenails and fingernails for aesthetic purposes dates back at least as far as Ancient Egypt, where henna and other products were applied to colour the feet and hands as well as the nails. Growing long fingernails has also been practised in Chinese and Hindu cultures, in part as a sign of leisure and status, since many forms of manual labour are difficult or impossible with long fingernails. Well-groomed nails have been a sign of cultivation and cleanliness for both men and women in American and European cultures as well. As a 1952 etiquette guide pronounces, ‘A fastidious man … keeps his nails clean and short with the cuticle pushed back. If he has his nails professionally manicured, they may be buffed but should never have any coloured or even colourless polish applied’. Coloured and clear nail enamel, or ‘polish’, became popular for women in the early twentieth century, and often replaced the literal polishing of nails with a buffer. False and elaborately painted nails are also now popular among some cultural groups.

In folk beliefs, the nails are often said to continue to grow after death. For instance, long fingernails, or sometimes no nails at all, are characteristic of vampires, revenants, and other beings of ‘undead’ status. In fact, in decomposition the tissues of the body dehydrate and contract, giving the appearance that the nails, hair, and teeth have ‘grown’. Sometimes the nails are sloughed off with the outer layer of skin, leaving exposed what appears to be new skin or nails, another sign of preternatural ‘life’ in a corpse. This same phenomenon is also the explanation for stories of dead bodies supposedly having come to life in the coffin and having either chewed off their nails in anxiety, or having scraped them off trying to escape. To keep the nails in place, Ancient Egyptian embalmers sometimes either tied the nails to the fingers and toes, or covered them with metal thimbles.

— Sarah Goodfellow

The little white specks, sometimes seen on the nails of the left hand, signify gifts on the thumb; friends on the first finger; foes on the second; lovers on the third; a journey to be undertaken on the fourth. This meaning given to specks on the nails was so widely known that many people called the marks ‘gifts’ or ‘presents’. The first documentary evidence for the belief occurs in Ben Jonson's play The Alchemist ((1610, I. iii) and Sir Thomas Browne was sceptical about it as one of his ‘vulgar errors’ (Pseudodoxia Epidemica (1672 edn.), book 5, chapter 23). The belief was still being reported at least as late as the 1960s. Other meanings have been given to the marks, however. In Melton's Astrologaster ((1620), 45), he writes ‘… to have yellow speckles on the nailes of ones hand is a great signe of death’.

A widely reported and relatively constant belief about babies' nails is that you must not cut them before the child is a year old, the mother must bite them off to keep them short. If you ignore this advice, the child will grow up to be a thief. The first written references occur in the mid-19th century (e.g. Denham Tracts, 1895: ii. 24) and it was still being reported in the 1980s. A slightly different idea was noted from a Dorset woman and included in N&Q (1s:4 (1851), 54): she was seen cutting her children's nails over an open Bible, and was asked why, ‘I always, when I cut the nails of my children, let the cuttings fall on the open Bible, that they may grow up to be honest. They will never steal, if the nails are cut over the Bible!’

Removable parts of the body such as hair and fingernails are particularly useful for anyone wishing to harm you with any form of witchcraft and should therefore be disposed of carefully. On the other hand, their intimate association with the person means they are also useful in cures. The idea that it matters when you cut your nails is also as old as the 16th century. Most authorities agree that Monday is the best day, and Friday and Sunday should be avoided at all costs. Some have a useful rhyme such as the following from East Anglia:

Cut them on Monday, you cut them for health
Cut them on Tuesday, you cut them for wealth
Cut them on Wednesday, you cut them for news
Cut them on Thursday, a new pair of shoes
Cut them on Friday, you cut them for sorrow
Cut them on Saturday, see your true-love tomorrow
Cut them on Sunday, the devil will be with you all the week
(Forby, 1830:411)

1. a rod of metal, bone or other material used for fixation of the ends of fractured bones.
2. see horseshoe nail (below).
3. a horny cutaneous plate overlying the dorsal surface of the distal phalanx of the human fingers and toes; similar structures are found in other primates.
4. (loosely) one of the claws of dogs, cats, chickens, etc.

• n. bed infection — see paronychia.
• n. bind — usually used to indicate a nail prick of the horse's hoof caused by the blacksmith driving a nail too close to the soft tissues and causing pressure on the sensitive laminae without penetrating them. See also nail prick (below).
• n.-hole curette — a curette with a fine stem and a tiny, half-cup shaped end designed to be inserted in a nail-hole in the hoof to curette out damaged tissue and to provide drainage. Called also Hughes nail-hole curette.
• n. dermatophytosis — see onychomycosis.
• horseshoe n. — a nail made of a special soft metal and with a specific shape that directs the point of the nail away from the soft tissues and out through the side wall of the hoof.
• interlocking n. — an intramedullary nail secured by transverse screws through the proximal and distal fragments.
• intramedullary n. — one placed within the medullary cavity, bridging the fracture site and providing support and immobilization although rotation may be a problem. See internal fixation.
• n. prick — penetration of the sole of the horse's hoof by a nail or other sharp object to the depth of the sensitive laminae. Causes acute lameness and may lead to infection, hoof abscess and tetanus. See also nail bind (above). Called also nail tread.
• pulled n. — an injury common in racing Greyhounds, in which the attachment of the nail to the nail bed is separated by trauma. Causes severe pain and lameness.
• n. tread — see nail prick.
• n. trimmers — see resco nail trimmer, toenail scissors.

For other uses, see Nail.

"Fingernails" redirects here. For the album, see Fingernails (album).

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2007)

A nail is a horn-like structure at the end of an animal's finger or toe. See also claw.

Contents 1 Parts of the nail 2 Growth 3 Health and care 4 Fashion 5 Medical test 6 References 7 See also

Parts of the nail

Fingernails.

Toenails.

Anatomy.

Fingernails and toenails are made of a tough protein called keratin, 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 This is the only living part of the nail. It is situated behind and underneath the Nail Fold and produces protein keratin which makes up the Nail Plate. If the matrix is ever damaged in any way, it would affect the Nail Plate growth.
• Eponychium This is the dead skin that forms around the cuticle area. This can be lifted and trimmed during a professional manicure treatment. Tends to be more prominent on males.
• Peronychium This is the 'live' skin that folds around the cuticle area giving protection to the Matrix.
• Hyponychium, Is 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 Is the hard and translucent portion which is composed of layers of protein keratin.
• Nail bed The Nail Bed is responsible for the 'pinkish' colour of the Nail Plate. It also determins what shape the nail will grow.
• Lunula Tends to only be visible in larger nails. Is the whitish crescent shape around the base of the nail plate, is the shadow of the Matrix.
• 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 Acts as 'runners on drawers' and guides the direction of nail growth. They are situated down the sides of the Nail Fold.

The only living part of a nail is situated 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,^[1] 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 a month.^[2] 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.^[3] 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.^[4]

This growth record can show the history of recent health and physiological imbalances, and has been used as a diagnostic tool since ancient times.^[5] Major illness will cause a deep transverse groove to form across the nails. Discoloration, thinning, thickening, brittleness, splitting, grooves, Mees' 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 degenerate (onychodystrophy); for further information see nail diseases.

Health and care

Mechanical injury can result in the nail being dropped.

Nails can dry out, just like skin. They can also peel, break and be infected. Toe infections, for instance, can be caused or exacerbated by dirty socks, specific types of aggressive exercise, tight footwear, and walking unprotected in an unclean environment.^{[citation needed]}

Manicures and pedicures 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 clippers, and nail files. Artificial nails can also be appended onto real nails for cosmetic purposes. The nails can improve their condition, in terms of hardness and nutrition, if they have contact with minerals.^{[citation needed]}

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 Rick Lopes, a spokesperson for the California Board of Barbering and Cosmetology.^[1] 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.^{[citation needed]} Like any other nail, it can be cut using a nail clipper.

Fashion

Main article: Manicure

Long, manicured nails are a fashion statement.

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 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 BC.

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. Since longer nails are considered more fashionable, some people try to avoid this bad habit by using different methods. They may apply bitter tasting varnish to their nails, make a new year's resolution to stop biting them, or get people to sponsor a nail.

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 dehydrated or in shock.^[6] However, this test is not considered reliable in adults.^[7] This is known as the CRT or blanch test.

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 hypovolemia ^[8][9]

References

1. ^ American Family Physician, May 15, 2001
2. ^ Toenail Definition - Medicine.net
3. ^ Hunter, J. A. A., Savin, J., & Dahl, M. V. (2002). Clinical dermatology. Malden, Mass: Blackwell Science. p. 173. ISBN 0632059168
4. ^ Nail growth usd.edu
5. ^ American Academy of Dermatology - Nail Health
6. ^ Monterey County EMS Manual. Chapter XI, Patient assessment.
7. ^ Schriger DL, Baraff LJ (Jun 1991). "Capillary refill—is it a useful predictor of hypovolemic states?". Ann Emerg Med 20 (6): 601–5. doi:10.1016/S0196-0644(05)82375-3. PMID 2039096. http://linkinghub.elsevier.com/retrieve/pii/S0196-0644(05)82375-3. 
8. ^ MedlinePlus Encyclopedia Capillary nail refill test
9. ^ St. Luke's Hospital. Capillary nail refill test.

• Barker D (2007). "Nail biology and nail science". Int J Cosmet Sci 29 (4): 241–75. doi:10.1111/j.1467-2494.2007.00372.x. 
• Haneke E (2006). "Surgical anatomy of the nail apparatus". Dermatol Clin 24 (3): 291–6. doi:10.1016/j.det.2006.03.007. PMID 16798426. 

See also

Wikimedia Commons has media related to: Nails

• Leukonychia
• Nail disease
• Hangnail
• Lunula
• Nail biting

v • d • e Integumentary system Skin Epidermis Stratum corneum · Stratum lucidum · Stratum granulosum · Stratum spinosum · Stratum basale Basement membrane zone Basal keratinocyte · Lamina lucida · Lamina densa Dermis Papillary · Reticular Subcutaneous tissue Panniculus adiposus · Panniculus carnosus Adnexa Glands Sweat glands: Apocrine · Eccrine Sebaceous Hair Outer root sheath Inner root sheath Shaft Cuticle · Cortex · Medulla · Bulb with matrix cells · Hair papilla Muscle Arrector pili Nail Matrix · Lunula · Nail plate · Eponychium · Paronychium · Hyponychium Other Skin flora

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