The nervous system of the skin

Harboring the sensory nervous end organ, the skin establishes contact to our environment. The perception of touch, temperature and pain is enabled by a complex network of sensory nerve fibers, which terminate mainly as free nerve endings or as specialized end organs such as Meissner corpuscles or touch domes. Each axon is ensheathed by a Schwann cell, which represent the glial cells of the peripheral nervous system. In the hairy human skin, these are mainly non-myelinating Schwann cells, which ensheath the peripheral nerves as well as their free nerve endings. Here, each Schwann cell ensheaths several sensory axons, a structure known as Remak bundles. A myelinating Schwann cell, in contrast, ensheathes only one axon and these are found supplying for example touch domes and Meissner corpuscles. By using sheet preparations of human skin, we are able to depict and analyse the nervous system of the skin, in particular the subepidermal nerve plexus in situ, and over several cm2. Using immunohistochemistry and immunofluorescence to depict cytokeratin 20 on the epidermal sheet and protein gene product 9.5, neurofilament, nerve growth factor and other markers on the dermal sheet, we have succeeded in establishing a novel method with which to characterize touch domes in human hairy skin.