Direction of Nail Growth and Thickness

The matrix cells point at an angle toward the cuticle as shown in Figure 2.3. This creates the flat and thin shape of the plate. The length of the matrix determines the thickness of the natural nail plate. Figure 2.4 shows how this occurs. Clearly, the matrix making the longest row of cells will have the tallest stack of cells in the plate. Of course, a real nail plate has thousands of packed cell layers.

Look closely at Figure 2.4 and you will see something else interesting about nail plate growth. This diagram shows that the cells near the back of the matrix have much further to travel before they get to the free edge. The cells coming from the back of the matrix end up on top of the plate. Since they travel further, they must be older than cells below them. At the free edge the surface plate cells are nearly two months older than the cells on the bottom side. This may explain why thin, dry nail plates tend to peel at the top surface, rather than from underneath.

How Does the Nail Plate Grow?

As keratin cells are pushed from the matrix they begin to change. They slowly lose their plump, round shape, as shown in Figure 2.2. When they flatten, most of the whitish material inside the cell is lost. They become thin, flat, transparent nail cells. If you recall, the distal part of the matrix is just below the lunula. Most of the lunula area cells haven’t completely flattened or lost their inner material. This explains why the lunula is whitish and cloudy. When the cells flatten, they also become more compact. Older cells pack together more tightly making the nail plate harder or more dense, so near the eponychium (proximal nail plate), the plate is softer. The free edge contains the oldest, flattest, and hardest cells.

It is very important to treat the area near the cuticle with care. It is thinner and softer than the rest of the plate. Also, the matrix is directly below this region. Remember, the eponychium tissue is a barrier against bacteria and other microscopic invaders. It must not be broken or harmed. Always use caution with any procedure involving this area of the nail unit. Damage here can permanently injure the nail unit.

For many years, it was believed that at least part of the nail plate grew up from the nail bed. Every cell in the nail plate comes from the matrix. The only exception is the thin layer of epidermis that adheres to the bottom of the plate. This tissue becomes the solehorn found under the free edge of the plate.

The Role of Proper Circulation

The matrix needs a good blood supply in order to do its job. Arteries carry nutrients to tiny capillaries in the matrix. Capillaries are like long, one-way streets. They wind through tissue carrying blood. The matrix has two types of capillaries. One type delivers oxygen, and important nutrients to matrix cells. The other drains waste products and other contaminant’s away from the matrix.

The draining capillaries carry wastes to the veins. The impure blood flows through the kidney and liver where it is purified and returned to the heart. The heart pumps the blood to the arteries which circulates it throughout the body. This cycle runs continuously, 24 hours a day. Every cell in the body benefits from this cycle, including those of the nail unit. This is how the matrix is fed and cleaned. Obviously, proper circulation is a critical part of maintaining a healthy nail unit.

The Onychodermal Band

This feature of the nail unit is often missed. It can only be seen with careful observation. The onychodermal band is found in the nail plate, just before the free edge. Examine your own nails for this band. This thin band has a glassy-looking, grayish appearance. You will see this grayish band lying beside the nail plate’s white free edge. This is the seal between the nail plate and hyponychium. When this seal is broken, infection often occurs.

Nail Plate Growth

How fast does the nail plate grow? This is a difficult question to answer. Many factors affect the growth rate. For example, the nail plates of each finger grows at different rates. Nail plates also grow slower at night and during the winter. On the average, the normal thumb nail will grow about 1/10 inch per month or 1 l/2 inches per year. The left thumb nail usually grows slightly faster than the right. The index fingernail plate grows the fastest, followed by the pointer and ring finger, which grow at almost the same rate. The thumb’s is the next slowest, but the slowest of all is the little finger’s. It grows abou1t I/4 inches per year.A s a rule, the longer the finger the faster the nail plate will grow.

Nail plates grow about 20% faster in the summer. They also grow faster during pregnancy. Nail plate growth increases by about 3 l/2% between the fourth and eighth month of pregnancy. From the ninth month until after delivery, growth rate increases by 20%, regardless of season. After two or three weeks the growth rate drops back to normal. Age also affects the growth rate. Growth peaks between the ages of ten and 14 years and slowly declines after age 20. Nail-biting, accidental damage, or loss causes nail plates to grow faster. Men’s nail plates grow faster than women, especially on the dominant hand. Many factors cause slow growth of nail plates. For example, being immobilized or paralyzed, poor circulation, malnutrition, lactation, serious infections, psoriasis, and certain medications.

Some believe that certain foods, (i.e,, gelatin or using special creams and oils), will increase the growth rate. This is untrue. Although the nail plate requires certain nutrients for proper growth, there is little evidence that eating any particular foods will cause them to grow faster. Creams, oils, and lotions are sometimes sold as “growth accelerators.’’ These claims are false, misleading, and illegal! No cosmetic product may claim that it will change or alter any body function. These products and other cosmetics are for beautifying only, not healing. Only medical drugs can make such claims. Remember-no cosmetic-related product can heal, repail; grow, or make any other similar claim.

The Hyponychium

The farthest or most distal edge of the nail unit is the hyponychium. It is found under the free edge. The hyponychium is composed of epidermis tissue. As you know, this same tissue makes up the top layer of the nail be(ds ee Figure 1.2).

The hyponychium forms a watertight seal that prevents bacteria, fungi, viruses, etc., from attacking the nail bed. Care should be taken when manicuring under the free edge. Damage to the hyponychium can lead to infection. Once infected, the natural nail plate may lift or separate from the nail bed. It may even lead to loss of the nail plate.

Nail Blood and Nerve Supply

A rich supply of nutrients is delivered to the nail unit by the blood. Arteries carry blood from the heart to other parts oft he body. Two arteries supply each nail unit. A single artery runs along each side of the finger passing through the lateral nail fold. After leaving the nail fold, they run deep into the dermis (basement tissue) of the nail bed. Many small branches carry blood from the arteries to other parts of the nail unit. These tiny branches are called capillaries. The capillaries give the nail bed its pinkish color. The capillaries carry blood to the epidermis, just below the nail plate. The result is a healthy pink appearance. The capillaries do not reach into the nail plate. Therefore, the nail plate receives no blood or nutrients. Blood is drained away from the nail unit by veins. Veins collect blood from the capillaries and return it to the heart. The nail unit has two veins. Each lateral nail fold has its own vein. These veins carry blood and waste products away from the nail bed. Figure 1.5 shows the complex system of veins, arteries, and capillaries found in the hand and finger.

Nerves follow a similar path through the nail unit. Nerves provide the sensations of touch, pain, and warmth. They also move the muscles in the fingers and hands. The nerves end near the skin’s surface. The nerve endings are very sensitive. Some are sensitive to pain, some to pressure and others to heat. They relay these sensations back to the brain.

Solehorn

The epidermis remains attached to the underside of the nail plate until it grows past the fingertip. This epidermis can be seen by closely examining the underside of the free edge. This is called the solehorn or solehorn cuticle. The solehorn usually sloughs away on its own or may be removed during a manicure.

Nail Bed

The nail bed lies directly under the nail plate. It starts at the matrix and ends just before the free edge. Like skin, the nail bed is made of two types of tissue, dermis and epidermis. The dermis is the lower or basement layer of tissue (found just below the epidermis). The epidermis is the upper layer and is closest to the nail plate. These two skin layers have unique shapes. The dermis has many grooves or channels running from the lunula to just before the free edge. The epidermis has ridges or rails running the same direction. These ridges fit neatly into the channels found in the dermis as shown in Figure 1.4.

The dermis is attached to the bone underneath. Therefore, the dermis is locked into place and does not move. Thee pidermis is very different. its firmly attached to the underside of the nail plate. So, the epidermis moves with the nail plate as it grows. This happens because the ridges of the epidermis are free to slide in the channels of
the dermis.

As the nail plate grows, the channels act like many sets of train tracks, guiding the ridges of the epidermis. Besides keeping the nail plate “on track,” the grooves also hold the ridges in place. This prevents the nail plate from lifting off the nail bed. he nail bed does not add keratin cells to the nail plate. All nail growth occurs in the matrix under the proximal nail fold and lunula.