Nail Bed

The nail bed lies directly under the nail plate. It starts at the matrix and ends just before the free edge. Like skin, the nail bed is made of two types of tissue, dermis and epidermis. The dermis is the lower or basement layer of tissue (found just below the epidermis). The epidermis is the upper layer and is closest to the nail plate. These two skin layers have unique shapes. The dermis has many grooves or channels running from the lunula to just before the free edge. The epidermis has ridges or rails running the same direction. These ridges fit neatly into the channels found in the dermis as shown in Figure 1.4.

The dermis is attached to the bone underneath. Therefore, the dermis is locked into place and does not move. Thee pidermis is very different. its firmly attached to the underside of the nail plate. So, the epidermis moves with the nail plate as it grows. This happens because the ridges of the epidermis are free to slide in the channels of
the dermis.

As the nail plate grows, the channels act like many sets of train tracks, guiding the ridges of the epidermis. Besides keeping the nail plate “on track,” the grooves also hold the ridges in place. This prevents the nail plate from lifting off the nail bed. he nail bed does not add keratin cells to the nail plate. All nail growth occurs in the matrix under the proximal nail fold and lunula.