Intraepidermal nerves in human digital skin.

Intraepidermal nerve fibers of human glabrous digital skin were investigated using a new silver impregnation method. Nerves were observed to enter the epidermis without regional preference, and to extend into the stratum granulosum. They are non-varicose (smooth) or varicose and range from less than 0.2 micron to approximately 2 micron in diameter, with varicosities up to 3 micron in diameter. Some axons branch profusely within the epithelium, giving off fine branches of differing diameters, while others appear to remain unbranched. At least some intraepidermal axons are fine branches of larger axons taking a horizontal course below the epithelial layer. Others are, at least topically, closely associated with Meissner's corpuscles. At 57 nerves per mm2 surface area, the density of intraepidermal nerves found in this investigation is much greater than that reported in recent publications, and agrees closely with values given in several older studies.