The touch dome in human skin is supplied by different types of nerve fibers

Receptor end organs and free-nerve endings in the skin are the peripheral sentinels of the sensorial nervous system encoding for touch, temperature, and pain. Using a novel approach to analyze the outermost nerves of the skin, we visualized for the first time the distinct microanatomical structure of the touch dome of human hairy skin. The dermal nerve fibers of this slowly adapting type 1 mechanoreceptor were embedded in dermal protrusions that could be readily discerned by Laminin-5 staining. Concerning the nerves supplying the touch domes, we found, unexpectedly, that besides A beta-fibers, A delta- and C-fibers also were regularly present. The epidermis overlying the nerve convolutes showed a distinctive architecture of the rete ridges clearly demarcated from the surroundings and extending over 0.193 +/- 0.138mm(2) (mean +/- standard deviation). Within this area, 756 +/- 386 Merkel cells/mm(2) (mean +/- standard deviation) were present compared with less than 50/mm(2) outside the touch dome, demonstrating for the first time a highly discontinuous distribution of these cells in nonglabrous skin. Our findings strongly suggest that the receptive qualities of human touch domes exceed mechanosensation, and that they may serve as multifunctional nerve end organs in human skin.