Anatomy, Physiology, and Nail/Skin Disorders
The nail unit
Know the structures: the matrix produces the nail plate; the nail bed supports it; the cuticle seals the base; the eponychium is the living skin at the base; the hyponychium is under the free edge; the lunula is the visible portion of the matrix; the nail folds frame the sides. Fingernails grow about 3–4 mm per month; toenails grow more slowly. The nail plate is mostly keratin and has no nerves, which is why trimming does not hurt, but the surrounding tissue is sensitive.
Body systems and disorders
Understand skin layers, bones of the hand and foot, muscles, nerves, and circulation well enough to recognize danger signs. Common conditions include onychomycosis, paronychia, onycholysis, psoriasis, Beau's lines, koilonychia, and melanonychia. A manicurist does not diagnose or treat; refer when findings are new, painful, bleeding, discharging, or changing.
Traps
Questions swap the matrix and bed, or the cuticle and eponychium. They also confuse a fungal infection with psoriasis or a bruise. Do not treat a client with an active infection, and do not cut living tissue.
Rule of thumb: sudden, painful, swollen, streaked, or bleeding means refer.
Worked example: a dark streak under the nail that is new and widening is not a polish stain; refer for evaluation.