Chapter 3 of 520% of exam
Nail Anatomy, Disorders & Diseases
One fifth of the exam covers the structure of the nail unit, how nails grow, and the difference between a cosmetic disorder you may work around and a medical condition you must refuse and refer. Knowing the correct anatomical names is the fastest way to pick up points in this section.
The Nail Unit
The nail unit is everything that makes, holds, and protects the nail plate. Exam items usually give a definition and ask for the term, or point at a location and ask what it does. Learn each part by its job, not just its name.
Matrix
The matrix sits under the proximal nail fold and is the only part that produces new nail cells. Injure the matrix and the damage shows in the plate permanently, which is why you never pick, gouge, or press hard near the base.
Cosmetology anatomy fundamentalsNail plate and nail bed
The plate is the hardened keratin that we shape and polish; it has no nerves or blood supply. The bed is the living tissue underneath that supplies the plate and gives it the pink color.
Cosmetology anatomy fundamentalsLunula
The pale half-moon at the base is the visible front part of the matrix. It looks whitish because the thicker cells there hide the blood vessels beneath.
Cosmetology anatomy fundamentalsEponychium and cuticle
The eponychium is the living skin fold at the base that seals the matrix from bacteria. The true cuticle is dead tissue that adheres to the plate and can be gently pushed and removed.
Cosmetology anatomy fundamentalsHyponychium, free edge, sidewalls, and grooves
The hyponychium is the living skin under the free edge and it seals the nail bed from the outside. The free edge is the part extending past the finger. The sidewalls are the folds of skin along the sides and the grooves are the tracks the plate slides along as it grows.
Cosmetology anatomy fundamentalsNail Growth and Composition
Nails are made of keratin, the same hardened protein family as hair and the outer skin. A fingernail generally replaces itself over several months and a toenail takes considerably longer, so any advice you give about improvement has to be measured in months, not days.
Growth rate
Fingernails grow roughly a tenth of an inch per month on average and take about four to six months to fully replace. Toenails grow more slowly and can take a year or more.
Cosmetology anatomy fundamentalsWhat speeds or slows growth
Growth is generally faster in warm weather, in younger people, and on the hand you use more. Illness, poor nutrition, medication, aging, and injury slow it down.
Cosmetology anatomy fundamentalsRegrowth after injury
A nail lost to trauma usually regrows if the matrix is intact. If the matrix was destroyed, the new plate may be ridged, split, or may not return at all.
Cosmetology anatomy fundamentalsA healthy nail
A healthy plate is smooth, slightly flexible, translucent with a pink bed, and firmly attached along its length with no separation, pits, or unusual color.
Cosmetology anatomy fundamentalsNo treatment claims
Products can improve appearance and moisture, but licensees do not treat, cure, or diagnose. Describe what a product does cosmetically and refer anything medical.
BPC §7317Disorders You May Service With Care
A disorder is a cosmetic or structural condition with no active infection and no inflammation. These can usually be serviced, often with a modified technique, and are good opportunities for retail and home-care advice. If a client is in pain or the condition is worsening, refer them out anyway.
Ridges and furrows
Vertical ridges are common with aging and may be lightly buffed and filled with a ridge-filling base coat. Deep horizontal furrows, sometimes called Beau lines, follow illness or matrix trauma and should be handled gently, not aggressively buffed.
Cosmetology nail fundamentalsBrittle, split, and peeling nails
Dryness, overexposure to water and solvents, and aggressive filing cause splitting and layering. Recommend oil, gloves for cleaning, and gentle one-direction filing.
Cosmetology nail fundamentalsWhite spots and bruised nails
White spots from minor trauma or air pockets are harmless and grow out. A dark bruise under the plate from a known injury is left alone and grows out; a dark streak with no known cause is a referral.
Cosmetology nail fundamentalsBitten nails and hangnails
Bitten nails and torn cuticle can be serviced as long as the skin is intact and not infected. Trim only the separated hangnail and recommend oil and consistent care.
Cosmetology nail fundamentalsDiscolored or spoon-shaped nails
Yellowing from polish or smoking is cosmetic and can be buffed lightly and covered. A spoon-shaped or unusually curved nail with no clear cause is discussed with the client and referred if it is new or changing.
Cosmetology nail fundamentalsConditions You Must Refuse and Refer
Redness, swelling, heat, pain, pus, open skin, or anything that looks contagious means stop. Diagnosing is the practice of medicine and so is treating, so the entire response is one sentence: politely explain that you cannot service the nail today and recommend they see a physician or podiatrist.
Signs of infection: stop immediately
Redness, swelling, warmth, throbbing pain, pus, or any weeping open area around or under the nail means no service. This includes paronychia, the inflamed infected nail fold.
BPC §7317Fungal, bacterial, and viral conditions
Thickened, crumbling, discolored toenails, a green or black stain between an enhancement and the plate, athlete's foot, warts, and cold sores near the service area are all referrals. Working on them spreads them.
BPC §7317Open skin, ingrown nails, and severe damage
Do not service an ingrown toenail that has broken the skin or is inflamed, a nail separated from the bed, or any cut, sore, or blister in the service area. Ingrown nails that need to be cut out are treated by a physician or podiatrist.
BPC §7316Undiagnosed dark streaks and changing lesions
A new dark band running down the plate, a lesion that changes shape or color, or a growth under or beside the nail is referred promptly, without alarming language and without a diagnosis.
BPC §7317Never diagnose and never name a disease
Say what you see and what you cannot do. Telling a client they have a fungus or an infection is diagnosing and is outside your license.
BPC §7317Disinfect after any refused service
If tools, the table, or a spa contacted the affected area, clean and disinfect everything before the next client and discard anything porous.
16 CCR §979Hand, Arm, and Lower Leg Anatomy
Because manicurists massage the hand, forearm, foot, and lower leg, the exam includes the bones, muscles, nerves, and vessels of those regions. You do not need medical depth, but you do need the names and roughly where they are.
Bones of the hand and wrist
The wrist is made of eight carpal bones, the palm has five metacarpals, and the fingers have fourteen phalanges, two in the thumb and three in each of the other digits.
Cosmetology anatomy fundamentalsBones of the arm, leg, and foot
The upper arm is the humerus and the forearm has the radius on the thumb side and the ulna on the little-finger side. The lower leg has the tibia in front and the smaller fibula on the outside, and the foot has tarsals, metatarsals, and phalanges.
Cosmetology anatomy fundamentalsMuscles you work over
The flexors bend the fingers and wrist and the extensors straighten them. In the leg, the gastrocnemius forms the calf, the soleus lies beneath it, and the tibialis anterior runs along the front of the shin.
Cosmetology anatomy fundamentalsNerves of the arm and leg
The radial, median, and ulnar nerves serve the forearm and hand. The tibial and peroneal nerves serve the lower leg and foot. Numbness or tingling during massage means ease off and reposition.
Cosmetology anatomy fundamentalsCirculation and massage direction
The radial and ulnar arteries supply the hand and the popliteal and tibial arteries supply the lower leg. Massage generally moves toward the heart to support venous return, with light pressure over bony areas.
Cosmetology anatomy fundamentalsTest your knowledge
Practice questions on Nail Anatomy, Disorders & Diseases
Last updated: July 2026