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1. a rod of metal, bone, or other material used for fixation of the ends of fractured bones.
2. a hardened or horny cutaneous plate overlying the dorsal surface of the distal end of a finger or toe. The nails are part of the outer layer of the skin and are composed of hard tissue formed of keratin. Called also unguis.
Parts of the nail. From Dorland's, 2000.
Nail abnormalities. From Lammon et al., 1996.
ingrown nail see ingrown nail.
spoon nail a nail with a concave surface.


1. One of the thin, horny, translucent plates covering the dorsal surface of the distal end of each terminal phalanx of fingers and toes. A nail consists of corpus or body, the visible part, and radix or root at the proximal end concealed under a fold of skin. The underpart of the nail is formed from the stratum germinativum of the epidermis, the free surface from the stratum lucidum, and the thin cuticular fold overlapping the lunula representing the stratum corneum. Synonym(s): unguis [TA], nail plate, onyx
2. A rod of metal or other solid substance, used in operations to fasten together the fragments of a broken bone.
[A.S. naegel]


1. the horny cutaneous plate on the dorsal surface of the distal end of a finger or toe.
2. a rod of metal, bone, or other material for fixation of fragments of fractured bones.

ingrown nail  aberrant growth of a toenail, with one or both lateral margins pushing deeply into adjacent soft tissue.
racket nail  a short broad thumbnail.
spoon nail  one with a concave surface.


1. A slender rod used in operations to fasten together the divided extremities of a broken bone.
2. A fingernail or toenail.
3. A claw or talon.


Etymology: AS, naegel
1 also called unguis. A flattened elastic structure with a horny texture at the end of a finger or a toe. Each nail is composed of a root, body, and free edge at the distal extremity. The root fastens the nail to the finger or the toe by fitting into a groove in the skin and is closely molded to the surface of the dermis. The nail matrix beneath the body and the root projects longitudinal vascular ridges, which are easily visible through the translucent tissue of the body. The matrix firmly attaches the body of the nail to the underlying connective tissue. The whitish lunula near the root contains irregularly arranged papillae that are less firmly attached to the connective tissue than the rest of the matrix. The cuticle is attached to the surface of the nail just ahead of the root.
2 any of various metallic nails used in orthopedics to fasten together bones or pieces of bone.
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Orthopedics A cylindrical metal device constructed of stainless steel used to hold 2 or more pieces of fractured bone in place


1. One of the thin, horny, translucent plates covering the dorsal surface of the distal end of each terminal phalanx of fingers and toes. A nail consists of a visible corpus or body, and a radix or root at the proximal end concealed under a fold of skin. The under part of the nail is formed from the stratum germinativum of the epidermis, and the free surface from the stratum lucidum, with the thin cuticular fold that overlaps the lunula representing the stratum corneum.
2. A slender rod of metal, bone, or other solid substance, used in operations to fasten together the divided extremities of a broken bone.
Synonym(s): unguis [TA] , nail plate, onyx.


1. A rod made of metal, bone, or other solid material used to attach the ends or pieces of broken bones.
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2. A horny cell structure of the epidermis forming flat plates upon the dorsal surface of the fingers and toes. Synonym: onyx; unguis See: illustration

A fingernail or toenail consists of a body composed of keratin (the exposed portion) and a root (the proximal portion hidden by the nail fold), both of which rest on the nailbed (matrix). The latter consists of epithelium and corium continuous with the epidermis and dermis of the skin of the nail fold. The crescent white area near the root is called the lunula. The epidermis extending from the margin of the nail fold over the root is called eponychium; that underlying the free border of the distal portion is called hyponychium.

A nail grows in length and thickness through cell division in the stratum germinativum of the root. The average rate of growth in fingernails is about 1 mm per week. Growth is slower in toenails and slower in summer than in winter. Nail growth varies with age and is affected by disease and certain hormone deficiencies. The onset of a disease that briefly interferes with nail growth and development may be estimated by measuring the distance of the line (Beau line) across the nail from the root of the nail.

Differential Diagnosis

Changes in the nails, such as ridges, may occur after a serious illness or indicate defective nutrition. In achlorhydria and hypochromic anemia, excessively spoon-shaped nails that are depressed in the center may occur. In chronic pulmonary conditions and congenital heart disease, a spongy excess of soft tissue at the base of the nails may be associated with clubbed fingers. See: clubbing

Atrophy may occur as a result of hereditary or congenital tendencies. Permanent atrophy may follow injuries, scars from disease, frostbite, nerve injuries, and hyperthyroidism. Nail shedding is due to the same causes. Fragile or split nails often occur as a congenital condition or may be due to prolonged contact with chemicals or too frequent buffing or filing of the flat surface of the nail during manicuring. In a healthy person brittle nails are usually caused by exposure to solvents, detergents, and soaps. The brittleness disappears when the external causes are avoided. Dry, malformed nails may be due to trophic changes resulting from injury to a nerve or a finger or from neuritis, Raynaud disease, pulmonary osteoarthropathy, syphilis, onychia, scleroderma, acrodermatitis, or granuloma fungoides of the fingers. Transverse lines (Beau lines) may result from previous interference of nail matrix growth. These lines may be caused by local or systemic conditions. The approximate date of the lesion may be determined because it takes 4 to 6 months for the fingernail to be replaced. Chancre may be suspected if a small indolent ulcer appears near the nail, esp. if indurated and associated with enlarged lymph glands above the inner condyle. Quincke capillary pulsation, indicated by a rhythmic flushing and blanching under the nails, is seen most frequently in aortic regurgitation and often in anemia.

Discoloration of nails is seen in various medical conditions. Black discoloration may be seen in diabetic and other forms of gangrene. Blue-black discoloration is a common condition due to hemorrhage caused by bleeding diseases, such as hemophilia, or trauma. This condition may be painful and can be relieved by drilling a small hole in the nail at the site of the hemorrhage. A dental drill, the heated tip of a paper clip, or a similar rigid wire of small diameter may be used. Brown discoloration may be due to arsenic poisoning. Brownish-black discoloration often indicates chronic mercury poisoning due to the formation of sulfide of mercury in the tissues. Cyanosis of the nails usually indicates anemia, poor circulation, or venous stasis. Green staining of the nail fold or under the nail is associated with the growth of Pseudomonas in a wet area. Slate discoloration is an early manifestation of argyria, and intake of silver should be stopped at once. White spots or striate lesions may be due to trauma and are more frequently seen in women. Transverse white bands in all nails may be a sign of acute or chronic arsenic poisoning or, rarely, of thallium acetate poisoning. See: Mees lines

eggshell nail

A condition in which the nail plate is soft and semitransparent, bends easily, and splits at the end. The condition is associated with arthritis, peripheral neuritis, leprosy, and hemiplegia. It may be the only visible sign of late syphilis.

fungal infection of nail

See: infection

habit deformity nail

Disruption of the nail surface by the habit of abrading or stroking that area. This produces a wavy or washboard-like nail surface.

hang nail

Broken epidermis at the edge of a nail.

ingrown nail

Growth of the nail edge into the soft tissue, causing inflammation and sometimes an abscess. Ingrown nails may be due to improper paring of the nails or pressure on a nail edge from improperly fitted shoes. In many cases, this condition may be prevented by cutting the nails straight across.

intramedullary nail

A surgical rod inserted into the intramedullary canal to act as an immobilization device to hold the two ends of a fractured long bone in position.

reedy nail

A nail marked by longitudinal fissures.

Smith-Petersen nail

See: Smith-Petersen nail

splitting nail

A troublesome condition in which the brittle nails split easily. Polishing, buffing, or abrading the nail surface will weaken the nail; thus, these practices should be discouraged. Brittle nails should be soaked, preferably in bath oil, prior to cutting them.

spoon nail

A nail with a depressed center and elevated lateral edges. This condition may follow trauma to the nail fold or iron deficiency anemia or may develop naturally.
See: koilonychia for illus.


1. A protective and functional plate of a hard, tough protein, KERATIN, lying on the back surface of the last PHALANX of each finger and toe.
2. A steel rod used surgically to secure bone fragments in apposition.


a horny, keratinized layer protecting the distal end of each finger and toe in humans and most other primates. In other terrestrial vertebrates the nail is shaped into a claw or amalgamated into a hoof.


1. One of the thin, horny, translucent plates covering dorsal surface of distal end of each terminal phalanx of fingers and toes.
2. Generally, a metal rod, used in operations to attach fragments of a broken bone.


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.

nail bed infection
nail 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).
nail-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.
nail dermatophytosis
horseshoe nail
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 nail
an intramedullary nail secured by transverse screws through the proximal and distal fragments.
intramedullary nail
one placed within the medullary cavity, bridging the fracture site and providing support and immobilization although rotation may be a problem. See internal fixation.
nail 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 nail
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.
nail tread
see nail prick.
nail trimmers

Patient discussion about nail

Q. My nails are black- is it dangerous? Hi, I was diagnosed with colon cancer and now I receive chemotherapy. This morning I found that my nails are brown and blue, and other nails have white lines on them. Is that dangerous? Should go and see a doctor?

A. The chemo can cause several changes in your nail, e.g. make them brittle etc. You can find some more info at :

Q. my guy friend has a very sick looking toe nail, what should he do? its really thick and has ridges, its also dark yellow and it looks to me has thick toe jam too... ugh, he needs your help please!

A. It sounds like Toenail fungus. Symptoms of toenail fungus, which can be caused by several types of fungi, include swelling, yellowing, thickening or crumbling of the nail, streaks or spots down the side of the nail, and even complete loss of the nail. Toenail color can vary from brown or yellow to white with this condition. I suggest your friend goes to see a foot doctor. The doctor might remove as much of the nail as possible by trimming, filing or dissolving it. Medicated nail polish might be prescribed for a localized infection, but a serious infection will likely be treated with a prescription oral antifungal medication. Only in severe cases will surgical removal of the nail be recommended.

Q. what natural cure for toe nail fungus really works?

A. Haven't heard about anything natural that was actually provent in reliable, well controlled trial. Especially since natural medications usually aren't tested in this way, I'm not sure there can be an accurate and true answer for this question.

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