Nail Lunula

The lunula (half-moon) is the whitish, opaque area at the base (proximal end) of the nail plate. The plump, white keratin cells flatten like pancakes. When they flatten, most of the material inside the cell is lost. This is why the cells become transparent. The lunula is formed by cells that have not yet completely flattened or lost their inner material. Not all fingers have a lunula. On fingers with a lunula, the front end of the matrix is directly below the whitish area. The h u l a outlines the front part of the matrix. The lunula is usually seen on the thumb and index finger. Interestingly, you can tell if a person is right- or left-handed by which thumb has the largest lunula. The thumb with the largest lunula is on the dominant hand.

The lunula also determines the shape of the nail plate. Look at the shape of your lunula and compare it to the natural shape of the nail plate’s free edge. They are an identical match. Both the lunula and free edge are crescent shaped. As mentioned above, it is also the shape of the distal (front end) part of the matrix. Animals with different-shaped lunulas have nail (or claws) which also match in shape. Figure 1.3 shows the claw and lunulas hapes of six different types of primates.’ Notice that the shape of the lunula closely matches the free edge.

Nail Plate

The nail plate is mostly keratin, the same chemical substance that forms hair. Keratin is a protein made from amino acids. These special proteins form a strong, flexible material which we call the nail plate. The nail plate is made of many layers of dead, flattened cells. These plate-like cells are cemented to each other with a sticky substance. When many layers stick to each other they form a structure that resembles a mortar and brick wall. The nail plate is also called the natural nail.

After a keratin cells grows in the matrix it is pushed outward and slightly upward by newer cells. The new growth emerges from under the proximal nail fold at the eponychium (see Figure 1.2). As new cells leave the matrix, they push the older cells toward the fingertips. Eventually, each keratin cell will reach the end of the finger. The part of the nail plate that grows beyond the fingertip is called the free edge or the distal nail plate. Distal means “farthest from the attached end.” It is important to remember the difference between distal and proximal. Proximal means “nearest attached end”. Therefore, distal is the opposite of proximal. These words may seem strange at first, but they are important to understand.

The hard keratin plate protects the nail bed and fingertip. Thicker nail plates provide greater protection. Obviously, if the nail plate is thinned too much, it cannot properly protect the delicate tissue underneath. This is often seen in nails that are over manicured or filed. Over filing the natural nail is a leading cause of nail plate thinning and destruction.

When keratin cells leave the matrix they are plump and whitish in appearance. Before emerging from under the eponychium the cells flatten, become transparent, and lose their color. This explains why nail plates are normally colorless, except for the white half-moon at the cuticle.

Cuticle and Eponychium

The cuticle is a part of the proximal nail fold. Specifically, it is the skin that touches the nail plate. There is more to the cuticle than what is visible. As you have learned, the skin curls underneath to form the proximal nail fold (see Figure 1.1). The skin underneath the fold is different than the visible top surface. The underside of the proximal nail fold constantly sheds a layer of colorless skin. This shed skin attaches to the topside of the emerging nail plate. It then “rides” on the nail plate and seems to grow from under the fold. This is the true cuticle. The visible skin fold that appears to end at the base of the nail plate is the eponychium. Sometimes, this tissue is incorrectly called the cuticle. During a manicure, the eponychium is gently pushed back to expose the true cuticle which should be carefully removed. You will see later that improperly performing this part of the manicure causes many problems for clients. It can lead to service breakdown of artificial nails and may seriously damage the nail unit.

Nail Matrix

Directly below the proximal nail fold is a small area of living tissue called the matrix. The matrix is the most important part of the nail unit. The matrix produces cells that form the nail plateT. hese cells are much like those found in a shaft of hair.

The size and shape of the matrix determine the thickness and width of then ail plate. The wider the matrix area, the wider the nail plate. Therefore, the matrix of the thumb must be wider than the matrix area of the little finger. Also, longer matrices make thicker nail plates. A person who has naturally thin nail plates must have a very short matrix area. If the matrix becomes damaged in any way, the effects will be seen in the nail plate.

Nail Folds

The skin does not end at the nail plate. Instead it folds underneath and covers the emerging nail plate. This skin fold protects the new, emerging nail plate. This fold is part of the nail unit. It is called the proximal nail fold. Proximal means “nearest attached end.” The skin on either side of the nail plate is an extension of the proximal nail fold, called the lateral nail fold. In this case, lateral means “to the side.” Normally, the proximal nail fold has the appearance of smooth, healthy skin. It can be injured by cuts, nicks and bruises, or irritating chemicals. Once the proximal nail fold is damaged, bacteria, fungi, or viruses can attack and cause infection. The proximal nail fold forms a seal or barrier that protects the area where the nail plate is made.