Nerve · Thoracic spine

Spinal nerves

Nervi spinales

The thirty-one pairs of nerves that leave the spinal cord, one pair for almost every gap between two vertebrae, from the base of the skull to the tailbone. Each one is formed inside that gap where two roots meet — a dorsal root bringing sensation in from the body and a ventral root carrying movement commands out to it — so a spinal nerve is mixed from the moment it exists. It exists for barely a centimetre: almost immediately it divides again into a small dorsal ramus that turns backwards to the spine's own muscles and skin, and a much larger ventral ramus that runs forwards into the trunk wall or onward into a limb plexus. This is the last point at which the nervous system is still arranged strictly by body segment, which is why one irritated spinal nerve produces a complaint shaped like a stripe rather than like a limb.