An area of skin which sends most of its sensory input to the CNS from a single pair of spinal nerves Sensory signals travel from the skin, through dorsal root of spinal nerve, into spinal cord and up to the brain In physical assessment it helps determine: -If any segments of the spinal cord are not functioning -Which spinal nerves are affected Nurses test dermatomes with ice following spinal/epidural anaesthesia to check the level at which the anaesthesia is effective