A Complete Guide to Your Nail Anatomy

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Medically reviewed by Brendan Camp, MD

Your nails are the hard, protective covering over the soft tips of the fingers and toes. Fingernails and toenails are a type of skin appendage, meaning they are made with skin cells. The nails act like a tool to help you scratch and improve your sense of touch.

There are three main parts that make up your nail anatomy: the nail plate, the underlying nail bed, and the skin around the nail. In some cases, health conditions can affect the structure and health of your nails, increasing your risk of infection and abnormal nails.

Anatomy of the Nails

The nails are slightly curved and about 1 millimeter thick—not even thickness of a credit card. The length and width of your nails will depend on the size of your fingers or toes and how long you let your nails grow. Nails constantly grow, but aging and poor circulation can slow nail growth.

Fingernails grow about 3 millimeters every month. Toenails grow slightly slower. If you damage or lose a fingernail, the nail can take four to six months to grow back. Toenails take about 12 months to regrow.

Structure

The main part of your nail is called the nail plate. The nail plate is made of skin cells called onychocytes (a type of keratinocyte) that produce keratin. Keratin is a translucent, fibrous protein that gives nails their rigid structure. Nails appear pink due to blood vessels underneath the nail plate. As the nail extends beyond the skin, there are no longer any blood vessels underneath, which is why the tips of the nails appear white.

The top portion of the nail plate that extends over your fingertips is called the edge of the nail.

The white half-moon shape near the base of the nail plate is called the lunula. The lunula is the upper part of the nail root that extends underneath your skin. The bottom part of the nail root underneath the skin is called the nail matrix. The nail matrix creates new cells to help nails grow. About 80% of your fingernail is located above the nail root, and 20% of the nail (including the nail root and matrix) is underneath the skin.

Location  

The nail plate attaches to the nail bed, which is the soft, fleshy tissue area directly under the nail. The nail bed extends from the end of the nail root to the skin right under the edge of the nail plate. The nail bed contains pigment-producing melanocytes that give skin color, nerves, and blood vessels.

The vertical sides of the nail are surrounded by skin that slightly overlaps the nail plate, known as lateral nail folds. The small divet of skin at the base of your nail is called the proximal fold. The proximal fold is attached to the cuticle—the small band of tissue at the bottom of your nails’ half-moons. The cuticle helps connect the nail plate and skin.

Anatomical Variations 

People can be born with nail differences that cause thin, mishappen, fragile, or missing nails. Other people may notice nail variations later in childhood as the nails grow slowly.

Nonsyndromic congenital nail disorder 10 causes extremely thick nails that often look like claws. These nails also start to separate from the nail bed, and portions of the nails may be missing.

Nail-patella syndrome is a genetic disorder that often causes skeletal abnormalities of the knees, elbows, and pelvis. About 95% of people born with nail-patella syndrome are born with nails that are thin, fragile, ridged, or missing.

It is also possible to be born without fingernails or toenails, known as anonychia congenita. All of the nails can be missing, part of the nails may be missing, or just a few nails may be missing.

What Do the Nails Do?

The anatomy of your fingernails and toenails helps protect the nail plate from injuries and infections. The nails also offer functional purposes related to scratching, sensation, and fine motor skills with your hands and feet.

Nails increase your hands’ ability to feel pressure, handle objects, and defend yourself from a person or animal who might be attacking.

For some people, the nails also act as a canvas to apply nail polish for cosmetic purposes.

Associated Conditions

Chronic nail picking (onychotillomania) and nail biting (onychophagia) are common ways the nails become damaged or infected. But there are several health conditions that can affect the nails themselves, causing symptoms that change your nails’ color, shape, and strength. Conditions that directly affect the nails include:

• Nail fungus (onychomycosis): Fungal nail infections can affect the fingernails and toenails, causing thick, discolored, and fragile nails that crack or crumble. 
• Paronychia: This infection of the nail fold can lead to red or swollen tissue around the nail. Paronychia typically affects the fingernails. 
• Nail psoriasis: Psoriasis is a skin condition that causes itchy, scaly patches of skin. Nail psoriasis affects your nails, causing discoloration, separation, crumbling, and splitting.
• Ingrown toenails (onychocryptosis): This can occur when nail plates grow into the nail fold. Ingrown toenails can lead to red, swollen areas around the nails and painful infections. Ingrown nails are usually caused by improper nail trimming, tight shoes, or anatomical abnormalities.

Other changes to your nails, such as in shape or color, are often a response to an underlying condition affecting another part of your body or nutritional deficiencies. This is why nails are considered to be a part of your body that can give clues to your overall health. Conditions your nails can develop as a result of an underlying issue include:

• Nail lifting (onycholysis): With this, the nail begins to lift off the nail bed so that it is not completely attached, creating white discoloration. Nail lifting is often caused by a fungal infection, nail psoriasis, or nail injury. 
• Brittle nails (onychoschizia): Thin, soft nails that may split down the center of the nail are known as brittle nails. Harsh chemicals that have been exposed to your nails, aging, nutrient deficiencies, nail psoriasis, and fungal infections can lead to brittle nails. 
• Nail pitting: This is when you develop dents in the nails. Nail pitting usually indicates you have a condition like psoriasis, atopic dermatitis, or alopecia areata. 
• Clubbing: This is when nails curve downward, causing the fingertips to swell. Clubbed nails may also feel spongy. Nails with this curve can be a harmless hereditary trait or a sign of a lung, heart, liver, stomach, or intestinal condition. 
• Beau’s lines: Deep grooves across the nail’s width indicate the nails have slowed or stopped growing. Injuries, chemotherapy, high stress, and fever can cause Beau’s lines. 
• Spoon-shaped nails (koilonychia): These are fingernails that dip in the center, making the nail plate resemble a spoon. Spoon nails are usually caused by an iron deficiency related to nutrition, stomach or intestinal conditions, celiac disease, or high altitudes.
• Onychomadesis: This is a severe gap across the nail’s width where the nail has stopped growing due to injury, stress, chemo, or illness. 
• Ram’s horn nails (Onychogryphosis): These are thick, overgrown nails that resemble small horns. They’re typically caused by psoriasis, ichthyosis, or circulation problems. The condition can also be hereditary. 

Nail Discoloration

Changes in nail color are often signs of underlying health conditions. For example, blue nails indicate you lack oxygen in your blood. Reddish half-moons can signal lupus, arthritis, or heart disease. Brown-black discolorations on the nail might mean there is melanoma skin cancer on the skin underneath the nail. If you notice a change in your nail color, consider contacting a healthcare provider for examination.

Diagnostic Testing

Consider seeing your healthcare provider if you notice any abnormal nail discoloration, ridging, breakage, or thickness. Abnormal fingernails and toenails are often signs of an underlying health condition that needs treatment.

Usually, a dermatologist—a doctor who specializes in conditions of the skin, hair, and nails—can help diagnose fingernail and toenail issues. A podiatrist—a doctor who treats foot and ankle issues—can help diagnose toenail issues.

Healthcare providers typically diagnose nail conditions by examining the nail. Sometimes they may want to take a biopsy to rule out infections, cancers, and inflammatory conditions.

A nail biopsy can include taking a sample of the nail plate or the nail matrix. Nail plate biopsies are less invasive and less likely to leave a scar. Nail matrix biopsies remove part of the base of the nail that’s underneath the skin. These biopsies are more invasive and risk permanently changing the nail’s shape and structure.

During either biopsy procedure, an anesthetic is injected into the nail area to numb you from any pain. Then, part of the nail plate or matrix is shaved off, removed with a scalpel, or punched out with a special pen-like tool. Dermatologists often use nail plate biopsies to diagnose nail psoriasis.

Tips for Keeping Your Nails Healthy

Good nail hygiene is a simple way to keep your nails healthy. Some everyday habits to keep your nails strong and intact include:

• Clean and moisturize your nails: Washing your hands, feet, and nails daily can help prevent infections. Follow up with a hand moisturizer to keep nails hydrated.  
• Trim your nails regularly: Use clippers to cut your fingernails straight across and to slightly round the tips. Toenails should be cut straight across. Trimming your nails also helps you avoid breaks. 
• Wear sandals in damp, public areas: Being barefoot in public pools or locker rooms increases your risk of toenail fungus. 
• Choose nail salons carefully: Visit clean salons and spas with experienced, licensed professionals. Make sure the businesses use sterile tools and disinfect pedicure foot baths before use. You can even bring your own tools for the nail technician to use.
• Wear gloves when cleaning: Covering your hands protects your nails from damaging moisture and harsh chemicals.
• Avoid biting and picking your nails: Kicking the habit is easier said than done, but try trimming your nails short or applying bitter-tasting nail polish to avoid biting your nails.

A Quick Review 

Nail anatomy includes the nail plate, nail bed, and surrounding tissue. The fingernails and toenails help protect the tips of your fingers and toes and improve fine motor skills. Keeping your nails healthy can help you avoid infections and permanent nail damage. However, many health conditions, like psoriasis and fungal infections, can affect the strength and shape of the nail. Nail changes can also be a sign of a serious health condition. If you notice any nail changes, contact your healthcare provider.

Read the original article on Health.com.