Anatomy of the Nail
I would like to know how many layers a nail has, and when the nail grows out, sometimes they have clear spots in them.what is the cause of the clear spots? Kari 2/04
The nail plate is formed by the Matrix Bed. For practical purposes this bed is divided into thirds, the proximal, intermediate, and distal matrix bed. The proximal matrix bed forms the top layer, the intermediate matrix bed the middle layer and the distal matrix bed forms the bottom layer of the plate. In this respect the nail plate could be said to have 3 layers but in reality, microscopically, the plate is composed of many, many layers when one considers the individual rows of cells from proximal to distal each forming a portion or layer of the plate.
The "clear spot" one may see in the nail plate is usually caused by a slight injury to a small area of the matrix bed from internal or external causes. The injury stops the nail growth for a short time in that small area leaving a "bubble" or "clear spot" area where there is no nail plate. It can be seen because of how light is refracted through the nail plate. One can tell what part of the matrix bed, i.e.: proximal, distal or intermediate matrix bed, was injured by the depth of the "bubble" or clear spot.
Psoriasis and Eczema may cause pits to be seen on the surface of the nail plate indicating that the disease has affected the proximal matrix bed. These conditions in there severe forms of course can affect any or all of the matrix bed causing deformities or even loss of nail plate. Other conditions such as arthritis or a bone spur, may cause injury to the intermediate matrix bed causing the clear spot or bubble to be in the middle of the nail plate and so on.
A clear understanding of nail unit anatomy and the functions of each of the 6 parts of the nail unit helps to determine a probable cause of a nail disorder.
Dr. Oscar Mix