9.1 Nail Structure
Key Takeaways
The nail plate is layered keratin with no nerves or blood vessels, so the plate can be filed without pain, while the nail bed and the nail folds cannot.
The matrix is the living tissue that produces the nail plate. The lunula is the visible pale half-moon of the matrix, and injury to the matrix can permanently change the plate.
The eponychium is living tissue at the base of the nail, the cuticle is dead tissue shed from the eponychium onto the plate, and the hyponychium is the seal under the free edge.
Standard instruction places fingernail growth at about 1/10 inch per month, roughly 2.5 to 3.5 millimeters, with replacement in about 4 to 6 months, while toenails may take 9 to 18 months, and Pennsylvania Code sets none of those rates.
The natural nail unit
The natural nail is an appendage of the skin. Standard nail-technology instruction divides the nail unit into the nail plate and the living skin that forms, supports, and seals it. You shape the plate. You do not file, cut, or push living skin as if it were plate. Pennsylvania salon rules govern sanitary practice. They do not name these parts, and they do not set a speed of growth.
Nail plate
The nail plate is the visible hard plate, built in layers of keratin. An over-filed plate peels, splits, or thins along those layers. It has no nerves and no blood vessels, so a healthy plate can be filed and buffed without pain. The nail bed and the skin folds around the plate do have nerves. Pain means the tool has left the plate.
The plate is translucent. Pink is the bed showing through. The free edge looks white because no bed lies under it. Standard instruction often places the water content of a healthy plate around 15 to 25 percent. That range is classroom teaching, not a Pennsylvania figure. Too little water and the plate is brittle. A waterlogged plate softens and separates from the bed more easily. Dry the plate before an enhancement so water is not trapped under the coating.
Matrix, lunula, and mantle
The matrix is the living tissue that produces the nail plate. It sits under the skin at the base, and new plate is pushed forward from there. Injury to the matrix can permanently change the plate. A break only in the free edge can grow out.
The lunula is the visible part of the matrix, the pale half-moon. It looks pale because the matrix is thicker there and hides the blood supply under it. A hidden lunula, by itself, is not a disease. The mantle is the skin covering the matrix. Do not cut it open.
Nail bed
The nail bed is the skin under the attached plate. It has nerves and blood vessels, and it does not produce the plate. The matrix grows the plate, and the bed only supports it. A thin bed epithelium helps the plate stay attached and is not a second matrix. A lift leaves living bed, not a gap to fill with product.
Folds, eponychium, and cuticle
Nail folds frame the plate. The proximal fold covers the base and the matrix. The lateral folds, or sidewalls, run along each side, and the plate edge rides in the nail groove beside each sidewall. A nick in a sidewall is a cut in living skin.
The eponychium is the living tissue at the base, where the proximal fold meets the plate, and it helps seal the matrix. The cuticle is the dead tissue that sheds from the eponychium onto the plate. It is the colorless film on the plate, not the pink skin behind it. Nail-technology instruction keeps those two names separate. Remove only dead cuticle, and only on intact skin. Do not cut the living eponychium. Cutting it opens the seal, invites infection, and can harm the matrix.
Hyponychium and free edge
The hyponychium is the seal under the free edge. A sharp pusher, a probe, or a file dragged underneath can break that seal and open a path for infection. Clean gently and stop at the seal. The free edge is still plate, with no nerves. It is the part you shape or lengthen with a tip. Beyond the hyponychium, the tissue under the plate is living bed.
Growth ranges in standard instruction
Standard instruction teaches a range, not one official speed. Fingernails grow about 1/10 inch per month in textbook teaching, roughly 2.5 to 3.5 millimeters, and replace themselves in about 4 to 6 months. Toenails grow more slowly and may take 9 to 18 months to replace. Pennsylvania Code does not set a growth rate. Growth is often faster in summer and slower with age and with poor circulation. Those are general patterns, not Pennsylvania rules. A mark grows forward with the plate unless the matrix itself was injured.
Parts of the nail unit
| Part | In standard instruction | Service limit |
|---|---|---|
| Nail plate | Layered keratin; no nerves or blood vessels | File the plate only |
| Matrix | Living tissue that produces the plate | Protect it; injury can change the plate |
| Lunula | Visible pale half-moon of the matrix | Leave it; a hidden lunula can be normal |
| Nail bed | Skin under the plate; has nerves and blood; does not produce the plate | Do not file, cut, or fill it |
| Proximal fold and sidewalls | Skin framing the base and the sides | Do not nick the folds |
| Eponychium | Living tissue at the base | Do not cut it |
| Cuticle | Dead tissue shed from the eponychium onto the plate | Remove only this dead film, on intact skin |
| Hyponychium | Seal under the free edge | Do not break the seal |
| Free edge | Plate past the fingertip | Shape it; it has no nerves |
| Mantle | Skin covering the matrix | Do not cut it open |
A decision at the table
A client asks you to cut the cuticles off so the polish line looks bare. The tissue she indicates is pink and continuous with the skin at the base. A thin colorless film lies on the plate just ahead of it.
Modify the service. The pink tissue is the living eponychium, and the film is the dead cuticle. The skin is intact, so remove only the dead film and leave the eponychium. Proceed with filing the plate and the rest of the manicure. Refuse any cut into the living base.
Which part of the natural nail produces the nail plate?
Free edge
Hyponychium
Matrix
Nail bed
Why can a technician file the free edge of a healthy nail plate without causing pain?
The nail plate has no nerves and no blood vessels.
The lunula blocks sensation in the plate.
The free edge is the living eponychium, which has no nerves.
Pennsylvania Code sets a painless filing depth of 1/8 inch.
What is the cuticle?
The living seal of skin that lies under the free edge.
The pale half-moon that shows the matrix.
The living skin fold along each sidewall.
Dead tissue shed from the eponychium onto the plate.
Sections you finish are checked off in the contents.