Nails

diagram of nail dorsal view diagram of nail sagittal section

The distal end of each digit is protected past a strong plate of hard keratin, called a blast or nail plate, which grows out from a nail bed. The blast bed, is a specialised form of skin epithelium, and has the aforementioned iv layers of the epidermis of pare, with the blast plate being analogous to the stratum corneum layer.

The blast plate is made upwardly of tightly packed, hard, keratinized epidermal cells. It has a blast body, a free edge, and extends deep into the dermis at the proximal end to grade the nail root (or smash groove).

The proliferating cells in the nail root course the nail matrix, and their proliferation (in the stratum basale) make the nail elongate continuously (bluish arrows). As the cells here approach the dorsal surface of the nail, they are displaced distally (in the direction of the blue arrows), and are gradually transformed into hard keratin, causing the nail plate to lengthen and strengthen. This layer is thin enough for colour to show through from the vascular dermis below.

The white crescent at the proximal end is called the lunula. It is white because the underlying epithelium is thicker here, and the colour of the dermis does not show through from underneath.

The epithelium underlying the nail bed and nail plate, forms a continuous fold, first forming the cuticle or eponychium (epo=above) at the proximal end of the nail, overlying the blast plate , and so the blast bed underneath the nail plate and finally the hyponychium (hypo=below); a thickened region of stratum corneum that secures the nail to the finger tip, and lies beneath the nail plate.

This photo shows an H&East section through a finger (sagittal), merely the boom itself has been removed.

Can you lot identify the epidermis and dermis, phalanx, eponychium, hyponychium, and nail root?

The photo on the right manus side shows a transverse section through a nail. Can yous place the prominent epidermal ridges?

In this section, the blast is present, tin you identify information technology?.