Can you tell me the function of the dorsal root of the spinal nerve?

Lets you feel things. The nerve root has 2 "ganglions". The dorsal root is on the posterior side of the nerve (closer to your back) and carries the fibers that allow you to feel things in your extremities (for example: pain, temperature, vibration). The information is transmitted to your brain so you understand what type of sensation is being encountered by the extremity.
It is the region. Where the neurons are located for the spinal nerves that send signals to the brain and the ganglion is very sensitive to pressure and ph changes or acidity.