Final answer:
The dorsal rami of spinal nerves specifically innervate the skin and muscles of the back. They contain sensory neurons from the dorsal root ganglia and motor neurons from the spinal cord that support functions and sensations in that region.
Step-by-step explanation:
The dorsal rami of spinal nerves are responsible for innervating the skin and muscles of the back. Contrary to the ventral rami, which extend outward to form various nerve plexuses that serve the limbs and body wall, the dorsal rami specifically target the intrinsic musculature and skin directly posterior to the spine.
The sensory neurons of the dorsal rami originate from the dorsal root ganglia and enter the spinal cord via the dorsal nerve root to relay sensory information from the back to the brain. Meanwhile, the motor outputs from the motor neurons found in the ventral horn of the spinal cord go through the ventral nerve root but it is the dorsal rami that innervate the epaxial muscles, not the appendicular muscles of the limbs or muscles of the face.