Bundles of nerves and vessels always supply a specific area of the skin. These areas, not visible to the naked eye, are called dermatoma. Many diseases spread alongside the dermatoma of the skin, e.g. zoster. That`s why knowledge of the dermatoma is important for diagnostics. The word dermatome is used twice: For the derivatives of the somites, and for the skin areas that are afferently supplied by nerve fibers of a specific spinal segment.