Matrix of nail

Nail matrix

The nail matrix is the germinative portion of the nail complex, giving rise to the nail plate.  The matrix is at the most proximal point of the nail bed and is seated deep beneath the PNF; it is separated from the distal phalanx by only a few millimeters. According to Zaias, "the top half of the nail plate (the dorsal aspect) is derived from the proximal matrix, while the derivation of the lower half (the ventral aspect) is from the distal matrix." The proximal matrix continues proximally and laterally to form the lateral matrix horn. The nail surgeon should be cognizant that the lateral matrix horn may be extensive.

The lunula is an opaque, grayish white, half-moon–shaped structure that extends beyond the distal limit of the PNF. The lunula is usually seen through the transparent nail plate, especially on the thumbs and great toes, as the visible distal component of the nail matrix. The distal margin of the lunula must always be preserved during nail surgery if the normal shape of the nail is to be maintained  An active granular layer typically found in the PNF is missing from the nail matrix; therefore, keratohyaline granules cannot be found in the matrix. The basal cells of the matrix actively participate in the process of differentiation and keratinization to eventually produce the dead horny product, the nail plate.

Several reasons exist why the nail surgeon must attempt to leave the structural and functional boundaries of the nail matrix intact when performing nail surgery; some of the reasons include the following:

• The matrix is the center of nail formation and the source of the nail plate.
• Nail growth is a direct function of the rate of turnover of matrix cells. 
• Nail thickness is directly related to the length or the size of the nail matrix.
• The shape of the distal border of the lunula determines the shape of the nail. If this border is convex, the distal free edge of the plate will also be convex.

Disruption of any of these components of the nail matrix can result in scarring and onychodystrophy of the evolving nail plate. The most common indication for partial or complete destruction of the matrix is a recurring problem of ingrown nails recalcitrant to conventional therapies. The healthy matrix synthesizes a complete fingernail plate on an average of every 6 months.

Anatomy & Histology of nail