Skin, musculoskeletal system and all organs of the body are supplied by nerve fibers of the somatic and autonomic nervous system, each of the systems with its specific nerve fiber types, fiber composition, fiber density and targets. Experimental data support the hypothesis that tumor tissue might interact with nerve fibers. The peripheral nervous system possesses an extraordinary cellular equipment to protect the axons against pathological stimuli. Only restricted areas lacking a cellular barrier are weak points within the nervous network. Therefore, this article focuses on the functional morphology of the peripheral nervous system and its regional differences.