Arm nerve regions. Artwork of the muscles of the human body from the rear, with the right arm (right) labelled with the names of the spinal nerves (cervical, neck, C; and thoracic, chest, T) that supply them: C4, C5, T2. Dermatomes (colour-coded) are areas of skin supplied by spinal nerves. Numbered labels mark regions of the shoulder, arm and hand. For the front of the arm, see C016/6840.