nail plate

The keratin is the main component of the nail plate, which is also the largest
and most exposed part of the nail apparatus. However, a complex structure that exists underneath the nail plate can exhibit many pathologic conditions.

The nail plate is mainly produced by the nail matrix trough matrical keratinization.

The nail matrix is made of epithelial bulbs that are oriented backwards. It is thought
that this orientation is responsible for the oblique, rather than vertical, growth of the nail plate.

The nail matrix mainly consists of two parts: apical and ventral. Both exhibit a
mixed pattern of epithelial and hair keratin expression, but the ventral matrix has a well-defined prekeratogenous zone, while such area is more diffuse in the apical matrix.

The prekeratogenous zone is a “V-shaped” region encompassing the uppermost cell layers of the basal compartment and the lowermost layers of the keratogenous zone.

It is made of polygonal cells with a clear cytoplasm and oval nuclei arranged parallel to the nail plate.

While the prekeratogenous zone exhibits epithelial keratins, the keratogenous zone exhibits both types of keratins (epithelial and hair).

It is also debated the existence of a dorsal matrix, which might be a transition zone between the eponichium and the apical matrix. Such area of the matrix could actually be made of extensions from the apical matrix into the eponichium and from the eponichium into the apical matrix.

Although most of the nail plate is produced by the ventral matrix, the apical matrix produces the thin dorsal parts of the nail plate. The matrix contains melanocytes, Merkel cells and Langerhans cells.