The inexorable forces of human nail growth
Nails grow by a process of extrusion. As new, growing cells are added at the base of the nail, the older cells are pushed out toward the fingertip (or tip of the toe). The cells meet resistance as they emerge and join the established nail plate, growing flatter and longer. PHOTO | FILE
What you need to know:
- About 90 per cent, of the growth occurs on its underside at what is called the germinal matrix. This area of the nail bed is hidden by the fold of tissue that encloses the bottom of the growing nail, called the nail fold.
Q: What is the mechanism that moves growing nails forward?
A: Nails grow by a process of extrusion. As new, growing cells are added at the base of the nail, the older cells are pushed out toward the fingertip (or tip of the toe). The cells meet resistance as they emerge and join the established nail plate, growing flatter and longer.
The keratin protein in these cells grows harder, and beyond a certain point, they are no longer living cells with nuclei, just hardened structures.
About 90 per cent, of the growth occurs on its underside at what is called the germinal matrix. This area of the nail bed is hidden by the fold of tissue that encloses the bottom of the growing nail, called the nail fold.
The outer margin of the germinal matrix may be seen at the white “moon” at the base of the nail, known as the lunula. It is white because the cells there still have nuclei. The nail plate is loosely attached to the germinal matrix. It is also held in place by the folds of skin at the bottom and sides.
As it grows, the nail is forced into a concave shape. Cells that increase the shine of the nail surface are added at the top part of the nail fold. As the nail plate advances, it crosses over the sterile matrix, the part of the nail bed closer to the tip of the digit.
Here, the plate is strongly attached, in part by ridges in the matrix, and some more cells are added. Fingernails grow an estimated three to four millimeters a month, faster in summer, slower in older adults or when blood circulation at the base is poor. A complete nail takes about six months to grow.
