This is an excerpt from Pocket Atlas of Skeletal Muscles, The by Chris Jarmey.
Sensation from the skin is transferred to the spinal cord and hence to the brain by afferent nerve fibers (page 32) which are part of the mixed, motor, and sensory nerves, which make up the somatic peripheral nervous system.
All somatic nerves arise from one or more spinal segments and supply specific areas of skin. An area supplied by single spinal segment is called a dermatome but the nerves supplying a single dermatome may be carried in one or more individual nerves.
A good example of this is the C5 dermatome in the upper limb, which is supplied by the C5 fibers carried in both the upper lateral cutaneous nerve of the arm (axillary nerve) and the C5 fibers in the lower lateral cutaneous nerve of arm (radial nerve).
The dermatomes and the distribution of the individual nerves images that follow have been compiled by the publisher with the guidance and assistance of Dr Robert Whitaker, MA MD MChir FRCS FMAA, Anatomist, University of Cambridge.
Cutaneous Nerves of the Arm
Cutaneous Nerves of the Leg
Anterior and Posterior Dermatomes