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A spinal nerve ramus is a branch formed after a spinal nerve has been assembled from its dorsal root and ventral root. Both posterior and anterior spinal nerve rami carry mixed sensory and motor fibres. Posterior branches principally supply the back; anterior branches supply the anterolateral trunk and, through nerve networks, the limbs.^[ref]

A root and a ramus therefore describe different positions in the branching pathway. Fibres have already mixed before the spinal nerve rami separate. Many anterior branches contribute to a nerve plexus, redistributing axons from several spinal levels into named peripheral nerves. The branch points route existing fibres rather than forming new synapses.

A ventral root is a bundle of outgoing motor axons leaving the anterior side of the spinal cord. It contains somatic motor fibres and, at appropriate spinal levels, autonomic efferent fibres. It joins a sensory dorsal root to form a mixed spinal nerve.^[ref]

For example, an action potential destined for a limb muscle can leave the spinal cord through a ventral root, then continue through a mixed spinal nerve and an anterior spinal nerve ramus. The directional separation near the spinal cord does not mean every later branch is motor-only. A ventral root is also distinct from the anterior branch formed after the roots unite.