Nail and Skin Anatomy, Disorders and Diseases
Nail and Skin Anatomy
Nail structures you must name
- Nail plate - the visible hard keratin covering; it has no nerves or blood vessels, so filing it is painless.
- Nail bed - pink tissue directly beneath the plate; it is supplied with nerves and vessels, so injury here hurts and bleeds.
- Matrix - the tissue that produces the plate, extending under the proximal fold. It determines thickness and shape. Injury to the matrix causes permanent deformity.
- Lunula - the whitish half-moon; it is only the visible portion of the matrix, not the whole thing.
- Eponychium - the living tissue at the base of the nail; the cuticle is the thin dead seal on the plate. These are different structures and questions test that difference.
- Hyponychium - the seal under the free edge.
- Lateral folds and nail grooves - sidewalls that guide plate growth. The mantle is the pocket the plate emerges from.
Skin basics
The epidermis is the outer barrier layer; the dermis holds vessels, nerves, and glands; subcutaneous tissue lies beneath. Keratinocytes produce keratin, melanocytes produce pigment, sebaceous glands produce oil, and sudoriferous glands produce sweat.
Growth
Fingernails grow roughly 3 mm (about 1/8 inch) per month and replace in four to six months; toenails grow about 1 mm per month and take nine to twelve months. Growth is faster in youth, in summer, and during pregnancy, and slower with poor circulation or illness. The middle finger grows fastest.
Rule of thumb
The matrix is the factory. Protect it and never file or push deeply into it.
Disorders and Diseases
Disorder versus disease
A disorder is an abnormality that is not contagious - for example onychorrhexis (split, brittle nails), onychauxis (thickening), koilonychia (spoon nails), leukonychia (white spots), Beau's lines (horizontal depressions after illness), onycholysis (separation of plate from bed), onychophagy (biting), and onychocryptosis (ingrown nail). A disease is a medical condition, often contagious, requiring referral.
Infections to recognize
- Fungal: onychomycosis (thick, yellow, crumbly nail) and tinea pedis (athlete's foot).
- Bacterial: paronychia (red, swollen, pus-filled nail fold); Pseudomonas produces the green-to-black discoloration sometimes mistaken for mold.
- Viral: warts (HPV) and herpes whitlow (cold sores on the finger).
Scope limits
The manicurist recognizes and refers; you do not diagnose, treat, or apply medication. Signs of infection - redness, swelling, heat, pus, pain, discoloration with lifting - mean stop the service, do not work on the area, refer the client to a physician, and disinfect everything contacted.
Traps
- Green nail is bacterial (Pseudomonas), not mold or fungus.
- Paronychia is usually bacterial; fungal infections rarely cause acute pus-filled swelling.
- Onychomycosis and nail psoriasis look similar - another reason not to name a condition for the client.
- Warts and herpes are contagious; a service can be refused.
Worked example
A client's big toenail is thick, yellow, and separating from the bed. You do not trim aggressively or apply product. You explain what you observe, advise a physician, sanitize the station, and record the referral.