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- Nail anatomy: the seven parts of a nail and what each one does
Nail anatomy: the seven parts of a nail and what each one does
A nail is a plate of hard keratin made by the matrix, a strip of dividing cells under the skin at the base of the finger. The plate rests on the nail bed, is sealed at the back by the cuticle and at the front by the hyponychium, and the lunula is the visible end of the matrix. Fingernails grow about 3 to 4 mm a month.
The part of the nail you paint is the least alive part of it. The plate is dead keratin, pushed out over months by a factory of cells hidden under the skin. Everything that decides how a nail looks happens in that hidden factory and in the skin around it.
Knowing the parts makes nail care less mysterious. It explains why a knock at the base shows up as a white spot weeks later, why cutting the cuticle invites infection, and why a strengthener painted on the surface can only do so much. The names are Latin, but the jobs are plain.
What are the parts of a nail?
Anatomists call the whole structure the nail unit. It has seven parts that matter to anyone who cares for nails: the plate, the matrix, the lunula, the nail bed, the proximal nail fold with the eponychium, the cuticle and the hyponychium. The table gives each one, where it is and what it does.
| Part | Where it is | What it does |
|---|---|---|
| Nail plate | The hard, visible nail | Protects the fingertip; made of flattened keratin cells in layers |
| Matrix | Under the skin at the base, behind the lunula | Makes the plate; the only living, dividing part of the nail |
| Lunula | The pale half-moon at the base | The visible front edge of the matrix |
| Nail bed | The pink skin under the plate | Anchors the plate and gives it its colour |
| Proximal nail fold and eponychium | The skin fold at the base and its thin front edge | Covers and shields the matrix |
| Cuticle | The thin band of dead tissue stuck to the plate at the base | Seals the gap between fold and plate against water and microbes |
| Hyponychium | The skin under the free edge at the tip | Seals the front of the nail bed |
The lateral nail folds, the skin at each side of the plate, complete the frame; hangnails form there.
What is the nail plate made of?
The nail plate is the hard, keratinised structure made from compact, flattened cells called onychocytes, arranged in layers, according to the StatPearls anatomy reference. The cells are dead and full of hard keratin, the same protein family as hair, held together by lipids and by strong cross-links between the keratin fibres. The plate has no nerves and no blood supply of its own, which is why filing is painless.
The plate is slightly curved in two directions, across and along the finger, and that curve gives it stiffness. It is also porous. It takes up water quickly and loses it quickly, and each swell-and-shrink cycle strains the bonds between its layers. That is the mechanical reason wet work leads to peeling and splitting, a link covered in peeling nails.
Pigments from dark polish can lodge in those pores, which is why a base coat is used as a barrier. Nail oils work the other way: small, oily molecules such as jojoba wax esters slip between the layers and keep the plate flexible.
What does the matrix do, and why does it matter most?
The matrix is the strip of living tissue under the proximal nail fold where the nail is made. Its cells divide, fill with keratin, flatten and are pushed forward to become the plate. Nearly 90% of the plate is produced by the proximal half of the matrix, the germinal matrix, according to the Medscape reference on nail anatomy. StatPearls puts the figure at about 80% and explains the layering: the proximal matrix makes the top surface of the plate and the distal matrix makes the underside.
This division explains a lot of nail problems. A knock to the base of the nail bruises the matrix, and the cells it makes for a few days are faulty, so a white spot appears weeks later when that section reaches daylight. A fever or a course of chemotherapy pauses the whole matrix, and a groove across the nail (a Beau's line) grows out afterwards. A cut or a scar in the matrix can leave a permanent ridge or split. The proximal nail fold covers the matrix and, as StatPearls notes, protects it from trauma and from ultraviolet light.
The practical rule is to protect the base of the nail. Pushing a cuticle too hard, digging under the fold with a metal tool, or shutting a finger in a door all reach the matrix. The plate can be filed, buffed and painted; the matrix should be left alone. The everyday problems that start here are listed in the nail care guide.
What is the lunula?
The lunula is the pale half-moon at the base of the nail. It is the distal, or front, part of the matrix, seen through the plate, and it looks white because the tissue there is thicker and the blood vessels beneath are further from the surface. It is easiest to see on the thumbs and often hidden under the fold on the little fingers, which is normal.
The lunula is a landmark. A small or hidden lunula is common and means nothing on its own, and its size varies from person to person and finger to finger. A change in its colour, for example a blue or red tint, or a lunula that vanishes on all fingers at once, is worth mentioning to a GP.
What is the difference between the cuticle and the eponychium?
The eponychium is the living skin at the front edge of the proximal nail fold, the last strip of skin before the plate. The cuticle is the thin, dead, translucent band that grows out from under the eponychium and clings to the surface of the plate. Some references, including StatPearls, use the two names for the same thing, which is why the terms get muddled. In nail care the distinction is useful: the cuticle can be softened and pushed back; the eponychium is living skin and should be left intact.
Both form a seal. Water, detergent and bacteria that get past that seal reach the matrix, and an infection of the fold, paronychia, is one of the reasons the NHS gives for seeing a GP about a nail3. The American Academy of Dermatology advises against removing the cuticle for the same reason4. The method that keeps the seal and still gives a clean line of polish is in cuticle care without cutting.
What do the nail bed and hyponychium do?
The nail bed is the strip of skin under the plate, from the lunula to the fingertip. It is firmly attached to the underside of the plate and slides forward with it as the nail grows. Its dense blood supply gives the nail its pink colour, and its fine ridges lock into matching ridges on the underside of the plate. When that attachment fails, the plate lifts and turns white or yellow, a change called onycholysis that the AAD lists among the signs a dermatologist should examine.
The hyponychium is the skin under the free edge, where the nail bed ends. It seals the front of the nail bed in the same way the cuticle seals the back, and a plug of keratin and immune cells guards it. Cleaning too aggressively under the tip, or filing the free edge very short, can break that seal and let the plate lift, which is why dermatologists recommend a slightly rounded free edge of modest length.
How fast do nails grow, and what changes the speed?
Nail growth is estimated at 3 to 4 mm a month, and a complete fingernail takes about six months to replace, according to Medscape. Toenails grow at roughly half that rate, so a toenail can take a year or more to renew. Growth is faster on the longer digits, in summer, in people under 30 and in nail biters.
Growth slows with age, in cold weather, during illness and in poor circulation. Because the plate is a timeline, a dermatologist can date an event by measuring the distance of a groove or a spot from the cuticle: a mark 3 mm from the base was made about a month ago. The same arithmetic sets expectations for care. Oil, gloves and gentle filing improve the plate that is being made now, and that plate reaches the tip in three to six months.
What the growth rate means in practice
- A white spot near the base takes about six months to reach the free edge.
- A groove from an illness grows out in five to six months on fingers, longer on toes.
- Damage from peeled-off gel takes as long to grow out as the plate takes to renew.
- A change of routine shows its full result after one complete growth cycle.
- The matrix under the skin at the base makes the nail; the plate you see is dead keratin and cannot repair itself.
- Fingernails grow about 3 to 4 mm a month and take about six months to replace; toenails take roughly twice as long.
- The cuticle and the hyponychium are seals at each end of the nail bed, and both are best left intact.
- The lunula is the visible front of the matrix; its size varies from finger to finger and means little on its own.
- A mark on the nail can be dated by its distance from the cuticle, at roughly 1 mm a week.
Questions people ask
What is the nail matrix?
The matrix is the strip of living, dividing tissue under the skin fold at the base of the nail. It produces the nail plate, with most of the plate coming from its proximal half. Damage to the matrix shows up in the nail weeks later and can be permanent if the tissue scars.
What is the white half-moon on my nail?
The half-moon is the lunula, the front end of the matrix seen through the plate. It looks pale because the tissue there is thicker. It is most visible on the thumbs and may be hidden on the little fingers, which is normal.
Is the cuticle the same as the eponychium?
In everyday nail care they are treated as two things. The eponychium is the living skin at the edge of the fold; the cuticle is the dead, translucent band that grows from under it and sticks to the plate. Some anatomy texts use the words interchangeably.
How long does it take for a fingernail to grow back completely?
About six months for a fingernail, at a growth rate of 3 to 4 mm a month. A toenail grows at roughly half that speed and can take 12 to 18 months. Growth is faster in summer and in younger people.
Does the nail plate have nerves or blood vessels?
No. The plate is dead keratin, which is why filing it is painless. The colour comes from the nail bed beneath it, and the nutrients that build the plate arrive through the blood supply of the matrix, not through the surface.
Sources
- Anatomy, Shoulder and Upper Limb, Nails · StatPearls (NCBI Bookshelf), 2023
- Nail Anatomy · Medscape, 2013
- Nail problems · NHS, 2024
- 11 dermatologists' tips for healthy nails · American Academy of Dermatology, 2025
- 12 nail changes a dermatologist should examine · American Academy of Dermatology
