Lets learn about spinal nerves. Spinal nerves innervate most of the body with the exception of parts of the head and neck There are 31 pair of spinal nerves. Lets take a closer look. The spinal nerve is produced by 2 nerve roots exiting the spinal cord. There is a dorsal root and a ventral root. The dorsal root contains sensory or afferent fibers and the ventral root contains motor or efferent fibers. The cell bodies of the neurons of the dorsal root are in the dorsal root ganglion. The dorsal and ventral roots combine to form a short spinal nerve. The spinal nerve then branches. These branches are called rami. The dorsal ramus innervates the deep muscles and skin of the back. The Ventral ramus innervates intercostal nerves and forms plexuses. There are also 2 branches collectively called the rami communicantes which have to do with the autonomic nervous system. The spinal nerves carry sensory information from specific areas of the body called dermatomes. Spinal nerves are named for where they exit the spine. The dermatomes have the same name. For example the C5 spinal nerve corresponds to the C5 dermatome. Here is a picture of the plexuses formed by the ventral rami. Here we see the cervical and brachial plexuses. Here is a close up of the brachial plexus which supplies the nerves to the arms. Notice that the ventral rami of the spinal nerves enter and the nerves to the arm exit the brachial plexus. Here is a close up of the lumbar and sacral plexuses. The rami communicantes send fibers to the sympathetic ganglia which are located outside of the spinal cord. These ganglia are part of the sympathetic division of the autonomic nervous system. There is also a meningeal branch that re-enters the spine to innervate the meninges and blood vessels. WE hope you have learned something about spinal nerves and see you next time.