Dermatome skin sensory areas, illustration. The skin on the human body is divided into sensory areas called dermatomes, with each dermatome supplied by a single spinal nerve. These are divided into spinal regions: cervical (C), thoracic (T), lumbar (L) and sacral (S). There are 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. The fifth cranial nerve, the trigeminal nerve, emerges directly from the brain and is divided into the ophthalmic (V1), maxillary (V2), and mandibular (V3) nerves.