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SUMMARY
Nail are important in many daily activities.
The nail unit consist of nail matrix, nail folds, nail bed and hyponychium, and any of these parts has a specific composition and functions.
Complete regrowth of a fingernail after avulsion can take 4 to 6 months, and up to 1 year for a toenail.
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TIPS FOR DIAGNOSIS
In the case of a nail disease that affects the matrix, the clinical signs appear on the nail plate.
In the case of a nail disease that affects the nail bed, the clinical signs appear under the nail plate or as onycholysis.
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DON’T FORGET
Nail matrix is responsible for the production of the nail plate.
Nail folds are responsible for the protection of the matrix.
Nail bed is responsible for the adhesion of the nail plate.
Hyponychium is responsible for the detachment of the nail plate at the level of the distal edge of the finger.
Nail ligaments can be involved in psoriatic arthritis.
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Nails have a defensive function, help the prehensile activity of small objects, are implicated in deambulation, and have an important cosmetic function (Fig. 1.1).
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What we commonly call the nail is actually the nail plate, the finished, fully keratinized product of the nail matrix. The nail unit consists of:
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– nail matrix: responsible for the production of the nail plate;
– nail folds: responsible for the protection of the matrix;
– nail bed: responsible for the adhesion of the nail plate during the growth of the nail;
– hyponychium: responsible for the detachment of the nail plate at the level of the distal edge of the digit1 (Fig. 1.2).
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The nail plate is a tough and elastic structure, flexible and resistant, which covers the back of the distal phalanx of the digits and which is continuously produced by the matrix. It has a rectangular shape, with a greater longitudinal diameter in the hands and transversal in the feet. The nail plate is made up of keratin rich in sulfuric amino acids and particularly in cystine. The keratins of the ...