Sympathetic trunk

The sympathetic trunks (sympathetic chains) are paired bundles of nerve fibers that run from the base of the skull to the coccyx just lateral to the vertebral bodies. The sympathetic trunks communicate with the ventral rami of the spinal nerves via rami communicantes.

At the superior end of the sympathetic trunks, a sympathetic plexus forms on the internal carotid artery and is carried into the skull through the carotid canal. The inferior ends of the sympathetic trunks lie in front of the coccyx and converge at the ganglion impar. Along the length of the sympathetic trunks are paravertebral ganglia.

The sympathetic trunks are a fundamental part of the sympathetic division of the autonomic nervous system. They allow sympathetic nerve fibers to travel to spinal nerves that are superior and inferior to the one in which they originated. Also, many splanchnic nerves arise directly from the trunks.