Nail and Skin Anatomy, Physiology, and Disorders
The nail unit
Learn the parts and their functions, because questions test them by function as often as by name. The matrix produces new nail cells and contains nerves, lymph, and blood vessels; its visible portion is the lunula. The nail plate is keratinized, has no nerves, and appears pink because it is translucent over the vascular nail bed. The eponychium (cuticle) is the living seal at the base, the hyponychium sits under the free edge, and the perionychium includes the nail folds and lateral nail grooves.
Growth rates: fingernails grow roughly one-eighth inch per month and are replaced in about four to six months; toenails grow more slowly and take about nine to twelve months.
Skin basics
Epidermis, dermis, and subcutaneous layer, in order from surface to deepest, and the functions of skin as a barrier, temperature regulator, and sensory organ.
Disorders a technician must recognize but never treat
Onychocryptosis (ingrown nail), onycholysis (separation of plate from bed), onychorrhexis (splitting), onychophagy (bitten nails), leukonychia (white spots), koilonychia (spoon nail), Beau's lines (transverse grooves after illness or trauma), paronychia (bacterial inflammation of the nail fold), and onychomycosis or tinea unguium (fungal infection). A dark streak or band under the nail (melanonychia) or any new, changing pigmentation is referred.
Traps
Confusing the lunula with the matrix; calling the cuticle nonliving tissue; treating a bacterial infection as fungal; and suggesting a technician can diagnose or prescribe.
Rule of thumb
Redness, pus, swelling, pain, separation, or a dark streak means no service. Identify, do not diagnose; refer to a physician and document the referral.