What Are Nails: How They Are Made, Functions And Disorders, Nail Structure And Anatomy

What Are The Functions Of The Nails?

Fingernails contribute substantially to the manipulative precision of the hand. Thanks to the presence of these foils we are able to manipulate very small objects, such as a pin. The nails also give the fingertips greater sensitivity, thanks to the rich innervation of the nail bed. Finally, these structures act as actual protective plates of the digital end.

How they are made

Nail Structure And Anatomy

The anatomy of the nail system is quite articulated and is made up of different parts, among which the main structures are represented by the nail matrix, the nail plate, the nail bed, the nail folds and the hyponychium.

Nail Matrix

The  nail matrix  plays a vital role as it generates the nail plate. It is formed by keratinocytes similar to those present in the basal and spinous layers of the epidermis and among which there are also Langerhans cells and melanocytes.
The matrix can be divided into three different parts: dorsal matrix, intermediate matrix (or germinal matrix) and ventral matrix (or sterile matrix).
The  lunula , on the other hand, is that part of the matrix visible from the nail plate which appears as a whitish crescent at the base of the nail. This color is probably due to the greater thickness of the nail, which prevents the blood from showing through, as instead happens in the other pink parts.

Nail Plate

The  nail plate  occupies the space delimited by the nail folds and has an approximately rectangular shape, however, there is great variability from individual to individual.
The nail plate is the most evident part of the nail and is formed by multiple cemented layers of corneocytes, filled with keratin fibers  immersed  in an amorphous matrix. These are dead cells, whose hardness and  resistance  are due precisely to the presence of keratin. For this reason the nail, although rather rigid, has a good flexibility.
However, it must be emphasized that with aging there is a progressive calcification of the nails, which become harder and more resistant.
The chemical composition is similar to that of hair. The lamina contains 7 to 16% water and, despite what one might think considering its hardness, it is 10 times more porous than the stratum corneum of the epidermis.
Although the external surface appears smooth to us, the nail plate has vertical grooves on the underlying face. These furrows make close contact with the nail bed, increasing its adhesion.
The part of the lamina that protrudes from the toes and detaches from the underlying nail bed is called the  free edge of the nail .
The part of the nail plate inserted into the epidermis is called  the nail root .

Nail Folds

The nail folds border the nail plate. It is possible to distinguish the  lateral folds  from the  proximal fold  which delimits the visible proximal limit of the entire nail apparatus.
The proximal fold consists of two epidermal layers: superficial and deep. The superficial epidermal layer has a cornified margin which extends over the nail plate giving rise to the eponymous . The latter – also known as  the cuticle  and commonly called cuticle – is closely adherent to the nail plate and prevents the passage of microorganisms and  fungi  into the root, thus avoiding the danger of infection and  inflammation .
The  nail grooves , on the other hand, represent the grooves where the margins of the nails fit.

Nail Bed

The  nail bed  is located below the nail plate and is made up of epidermal tissue without the granular layer. The dermis of the nail bed – richly vascularized – is directly anchored to the periosteum of the distal phalanx, consequently, there is no subcutaneous tissue in this area.
The superficial part of the nail bed has a series of ridges and grooves which correspond to analogous grooves and ridges on the deep part of the nail plate. The presence of these irregularities causes these two structures to be firmly anchored to each other, thus conferring a certain resistance to the nail apparatus.

Hyponychius

The hyponychium  represents that area (epidermal crest) which is located below the free edge of the nail and is interposed between the nail bed and the fingertips, forming a sort of barrier that protects the subungual structures from possible external aggressions .

Growth

How Do Nails Grow?

Nail Growth

As mentioned, nail growth is due to the proliferation of matrix cells. These cells are arranged in an inclined manner, so that the nail grows mainly in length and not in thickness.
Under normal conditions, growth is between 0.1 and 1 mm/day. However, fingernails grow faster than toenails, and thumbnails grow faster than other fingers.

Disorders And Pathologies

Disorders And Diseases That Affect The Nails: What Are They?

There are many disorders and diseases that affect the nails and can cause alterations both in the structure, in the color and in the nail function.
Under physiological conditions, the main alterations that can occur in the nails are usually linked to normal aging processes. In this regard, frequent alterations are represented by the appearance of vertically oriented streaks (grooves) and by the thickening of the nail itself.
When nail alterations, on the other hand, are not related to aging, the triggering causes could be of a traumatic or pathological nature, or could be attributable to the use of aggressive cosmetics or detergents. For example, the fragility of the nails can be a symptom of pathologies, just as it can be linked to the use of particularly alkaline household cleaners.
Similarly, even the chromatic alteration of the nails can represent the sign of any pathologies not yet diagnosed, just as it can be caused by the use of  low quality cosmetics (for example, nail polish ).
In any case, in general if the alteration affects only one nail, usually, there is a local problem; on the contrary, when the phenomenon is extended to all the nails it is probably an internal pathology.