Which part of the nervous system innervates the skin of the back?

The skin of the back is primarily innervated by the dorsal rami of the thoracic nerves. These rami are branches of the spinal nerves that emerge from the spinal cord and innervate the muscles and skin of the back. Each dorsal ramus directly supplies sensory fibers to the skin, allowing sensation in that area.

The thoracic dorsal rami provide the necessary cutaneous innervation to the posterior aspect of the trunk. This specific innervation plays a crucial role in sensory perception, including the ability to feel touch, temperature, and pain in the skin overlying the back.

In contrast, the other options don’t fulfill this function for the skin of the back: the ventral rami of cervical nerves primarily innervate the skin, muscles, and structures of the anterior neck and upper limb; cranial nerves mainly serve the head and neck region; thoracic sympathetic nerves are involved in autonomic functions, including the fight-or-flight response, rather than providing direct sensory innervation to the skin.