Nail and Skin Anatomy, Physiology, and Disorders
What makes the nail
Nails are made of keratin produced by the matrix, the living tissue at the base under the proximal nail fold. The nail plate is the visible hard keratin; the nail bed is the skin beneath it; the lunula is the visible whitish part of the matrix; the hyponychium seals the free edge; the eponychium is living skin at the base, and the cuticle is the thin dead tissue on the plate itself. The perionychium is the tissue around the entire nail.
Fingernails are replaced in roughly four to six months, toenails in about nine to twelve, and toenails grow about half as fast as fingernails. Nail plates grow fastest in warm weather and in younger clients, and slow with age and poor circulation.
Recognizing what you cannot treat
You are not diagnosing; you are deciding whether to serve or refer.
- Onychomycosis: fungal, thickened, discolored, crumbly - refer.
- Paronychia: red, swollen, painful fold, often bacterial - refer.
- Onychocryptosis: ingrown nail - refer.
- Onycholysis: plate lifting from the bed - refer for cause.
- Onychorrhexis: splitting/ridged plates - careful service.
- Leukonychia: white spots, usually minor trauma - serve.
- Koilonychia: spooned nails - refer.
- Melanonychia: a dark stripe under the plate - refer promptly.
Traps to expect
Calling the nail plate “living tissue,” saying the matrix is the visible white half-moon (that's the lunula), or offering a treatment plan for a suspected fungus. Also: blue nail beds suggest circulation problems - refer, don't polish.
Rule of thumb
Any redness, swelling, pus, pain, dark streak, or lifting means no service and a referral.