Nail and Skin Anatomy, Disorders and Diseases
Nail and Skin Anatomy
The nail unit
Know each structure by function, not just name. The nail plate is the visible keratinized covering; it has no nerves or blood vessels. The nail bed supports the plate and carries grooves that guide growth. The matrix produces the cells that become the plate, so matrix injury can permanently change nail shape or thickness. The lunula is the visible portion of the matrix, not a separate organ.
Soft tissue landmarks
The cuticle is the dead tissue clinging to the plate; the eponychium is the living fold at the base. The hyponychium seals the area under the free edge, the perionychium is the tissue surrounding the nail, and the lateral folds frame the sides. The nail grooves and nail sinus are the tracks the plate slides along.
Growth
Fingernails replace themselves in roughly three to six months, growing about one-eighth of an inch per month. Toenails take about nine to twelve months. Growth slows with age, illness, poor circulation, and cold; it speeds up in summer, during pregnancy, and in youth.
Skin
Learn the layers and functions. The epidermis includes the protective stratum corneum; the dermis holds nerves, glands, and vessels; subcutaneous tissue provides cushioning. Skin functions include protection, sensation, heat regulation, excretion, secretion, absorption, and vitamin D synthesis.
Traps
Common wrong answers say the lunula is part of the nail bed, the cuticle is living tissue, or the nail plate contains nerve endings. None are true. If a question asks which structure determines nail shape, the answer is the matrix.
Disorders and Diseases
Scope and language
A nail technician recognizes conditions and refers; only a physician diagnoses and treats. This distinction drives most exam items. Learn to describe what you see in objective terms and to name the condition accurately when it appears in an option list.
Common nail disorders
Onychocryptosis is an ingrown nail. Onychogryphosis is a thickened, curved ram's-horn nail. Onycholysis is separation of the plate from the bed. Onychomadesis is a complete shedding of the plate. Onychorrhexis describes brittle, split lengthwise ridges. Leukonychia is white spotting, often from minor trauma to the matrix. Koilonychia is a spoon-shaped nail, and Beau's lines are transverse depressions following severe illness. Pterygium is forward growth of the cuticle that splits the plate. Clubbing and splinter hemorrhages are systemic flags requiring referral.
Infections
Paronychia is inflammation of the tissue around the nail; bacterial paronychia shows redness, swelling, pain, and pus, while a fungal infection may show thickened, discolored, crumbling nail. Tinea pedis is athlete's foot, tinea unguium is fungal nail infection, and verruca plantaris is a plantar wart. Herpes simplex can produce a painful vesicular whitlow on the finger.
Decision rules
Refer rather than serve when you see pus, spreading redness, a red streak, fever, sudden dark discoloration, or a lesion that has changed. Contagious conditions such as warts, fungal infection, and active herpes are service contraindications. Never apply polish or enhancement over an infected nail to "seal it in."
Traps
Options often suggest treating a condition, applying product over it, or diagnosing it from a photo-style description. Choose referral every time.