What are Nails?

The claw-shaped keratinous plate positioned at the edge of the finger and toes are called the nails. These structures are identified mainly in the primates. The toenails and the fingernails are composed of tough guarding protein known as alpha-keratin, which is found to be a polymer present in the hoof’s claws and hair of the vertebrates. The distal phalanx is found to be protected by the action of the fingernail and it also guards certain soft tissues against various injuries.  Various precise movements are found to be enhanced by the presence of the fingernails.

Structure

The nail is composed of structures such as the nail matrix, nail plate, and the nail bed positioned beneath the grooves enclosing the structure. The matrix is found to be a teratogenous membrane and is the region of the nail bed located below the nail and possesses numerous nerves, blood vessels and lymph.  The matrix is associated with the formation of the cells that mediate the formation of the nail plate.  The thickness, length, and size of the matrix are influenced by the thickness and width of the nail plate.  The shape of the fingertip bone influences the shape of the nail plate, where the nail plate is found to possess numerous shapes in different individuals, and the shapes include hooked, arched and flat. The matrix has the capacity to continue the production of the cells with proper requirements. The formation of the newer nail plates will push the older plates, which undergoes certain changes and becomes translucent, flat and compressed. The lunula is the observable part of the matrix with a whitish tinge and is mainly observed in the thumb.  The nail bed is found to be positioned below the nail plate.

The nail plate is composed of two different types of tissues including the epidermis and the deeper dermis.  The deeper dermis consists of living tissues encompassing the glands and capillaries and the epidermis positioned below the nail plate and moves in the direction of the fingertip.  The dermis and epidermis are connected with the presence of longitudinal grooves known as matrix crests. The nail root is considered as the basal region of the nail positioned below the skin. The nail root is positioned in the nail sinus. The actively growing tissues positioned in the matrix are associated with the formation of the nail root. The nail plate is detected to be the toughest region of the nail and is mainly composed of translucent keratin protein. The presence of compacted dead cells is the reason for the flexibility of the nail. 

The distal edge positioned in the anterior marginal region of the nail plate results in the formation of the edge of the nail. The epithelial tissues positioned below the nail plate are called hyponychium. It is a concern with the development of a seal, which is concerned with the formation of the nail bed. A seal positioned between the hyponychium and the nail plate is called the onychodermal band.

Function

The fingertip, distal phalanx, and the tissues are guarded by the fingernails, the counter-pressure generated by the fingernails aid in various delicate movements of the finger.  The nail also functions as a counter-force as the finger meets while touching an object.  This elevates the sensitivity of the fingertip.  The nail is found to lack nerve endings and it aids in numerous scraping and cutting actions performed by the hand.  The nail is found to be highly permeable and is composed of seven to twelve percent of water and thus the cosmetic applied on the nails is risky. Various fungicidal agents are also found to pass through the fingernails. The physiological imbalance in the body can be analyzed by observing the condition of the fingernails. The infection of the fungus can cause the loosening of the fingernails.

The paronychium is the soft tissue border which surrounds the nails, and an infection developed in this area is called paronychia.  The hyponychium is the area positioned in the hypothesis and is the thickened region.  The nail wall is the skin fold which overlaps the proximal and lateral regions of the nail.  The lateral margin is positioned below the nail wall. The cuticle and the eponychium (the thick layer present at the end or base of the nails) are concerned with the formation of the protective seal of the nail. The cuticle is semi-circular layer composed of numerous dead cells.  The eponychium is prone to infection as it is composed of a small region of living cells.

Growth

The growing region of the nail is positioned below the skin at the proximal terminal of the nail below the epidermis and is the only living region of the nail.  The number of terminal phalanges determines the growth rate of the nails. The nail found in the index finger is found to possess an increased growth rate than other fingers. The lack of vitamin D, vitamin A, and calcium results in the brittleness of the fingernails. Absence of vitamin B12 results in the rounded nail ends followed by the darkened and dry nails.  The lack of vitamin B and A codes for the fragile nails with ridges positioned vertically.  Various multivitamins and biotin aids in the growth of strong nails.  The protein is found to be the materials associated with the formation of the nails. The lowered condition of hemoglobin elevates the whitish appearance of the nails, where the pink color is diminished. The essential fatty acid plays a major role in the formation of healthy nails. The absence of linoleic acid results in the flaking and splitting of the nails, the lack of iron will lead to the development of a pale color of the nails.

Context and Applications:

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for:      

• Bachelor of science (B.Sc.)
• Master of science (M.Sc.)

Related Concepts

Nail disease, Onychogryphosis, and cutaneous conditions.