Anatomy and Physiology of the Nail, Hand, and Skin; Nail Disorders and Diseases
Anatomy and Physiology of the Nail, Hand, and Skin
Nail structures
Nail plate (the visible body), nail bed (the skin beneath it), matrix (where cells are produced - it determines thickness, shape, and the free edge's form), lunula (the visible whitish portion of the matrix), cuticle (nonliving tissue on the plate), eponychium (living fold at the base), hyponychium (the seal under the free edge), sidewalls, and nail grooves. The nail plate has no nerves or blood vessels of its own; it draws nourishment from the bed and matrix.
Growth facts examiners use
Fingernails grow roughly 3 mm (about 1/8 inch) per month and replace in about four to six months; toenails grow more slowly and can take nine to twelve months. Growth is faster in summer, in younger people, and on the middle finger; slower with poor circulation, illness, or malnutrition.
The hand and arm
Know the phalanges, metacarpals, carpal bones; the flexor and extensor tendons; and the major arteries and nerves of the hand. Ligaments connect bone to bone; tendons connect muscle to bone. Recognizing normal anatomy matters because swelling, numbness, or a changed nail shape can signal a condition requiring referral.
Skin
Epidermis (outermost, including the basal layer where new cells form and melanocytes reside), dermis (blood vessels, nerves, glands, hair follicles), and subcutaneous layer. Sudoriferous glands produce sweat; sebaceous glands produce sebum. Melanin determines skin and nail color.
Traps
Questions swap the lunula for the matrix, or the eponychium for the cuticle. The matrix is the source; the lunula is only the visible part. Another trap: claiming the nail plate needs "breathing."
Rule of thumb
Matrix makes the nail; hyponychium seals it; break the seal and infection has a door.
Nail Disorders and Diseases
Disorder versus disease
The distinction drives the whole domain. A disorder is an abnormality in structure or function that is not necessarily contagious - many clients may still be served with care. A disease is a pathological condition, often contagious or systemic, that the technician does not treat. The technician's job is to recognize, not diagnose, and to refer.
Conditions to recognize
Onychomycosis (fungal infection of the plate, often yellow, thickened, crumbling), paronychia (red, swollen, painful nail fold, usually bacterial), onycholysis (plate separating from the bed), onychorrhexis (brittleness with longitudinal splitting), onychauxis (thickening), onychatrophia (wasting), onychogryphosis (claw-like overgrowth), koilonychia (spoon nails), leukonychia (white spots, usually trauma), melanonychia (dark longitudinal band - refer), Beau's lines (transverse depressions after illness or trauma), pterygium (eponychium creeping onto the plate), agnail or hangnail, bruised nail, and nail psoriasis with pitting.
The green nail trap
Green-black discoloration is typically Pseudomonas bacteria trapped under an enhancement or in a lifted area. It is a bacterial condition, not a stain, and the enhancement must come off and the client referred. Questions often call it a fungus or a disorder the technician can simply buff away.
Working rules
Do not apply enhancement over infected, inflamed, or broken skin. Do not share files or nippers on a client with a suspected infection; discard porous items. Disinfect implements as always, and document what you observed and whom you referred the client to.
Traps
"The technician can treat fungus with the right product," "all discoloration is a disease," "refer only if the client asks," and mixing up onycholysis with onychorrhexis.
Rule of thumb
If it is red, hot, swollen, painful, oozing, or has pus - stop, and refer. Recognize; never diagnose or treat.