Ganglia of sympathetic trunk

At a glance

English

Ganglia of sympathetic trunk

Latin (TA2)

Ganglia trunci sympathici

System

Nerve

Region

Neck

Side

Paired, left and right

About the ganglia of sympathetic trunk

The ganglia of the sympathetic trunk, also called paravertebral or chain ganglia, are knots of nerve cell bodies set at intervals along the two sympathetic trunks. Each trunk lies against the front and side of the vertebral bodies and reaches from the upper neck to the coccyx, where the two trunks meet in a single ganglion impar. The ganglia are grouped by region as cervical, thoracic, lumbar and sacral.

Their number is smaller than the number of spinal segments because neighbouring ganglia fuse. The neck usually has only three: superior, middle and inferior cervical ganglia. The thorax has about eleven, the lumbar region about four and the sacral region four or five. In many people the inferior cervical ganglion merges with the first thoracic to form the cervicothoracic or stellate ganglion, named for its star-like spread of branches.

Preganglionic sympathetic neurons sit in the lateral horn of the spinal grey matter from T1 to L2. Their myelinated axons leave in the anterior root, join the spinal nerve and pass to the chain through a white ramus communicans. Once in the chain, a fibre may relay in the ganglion at its own level, climb or descend to relay in another ganglion, or run straight through without relaying to join a splanchnic nerve bound for a prevertebral ganglion such as the coeliac or mesenteric ganglia. A single preganglionic fibre can contact many postganglionic cells, which helps explain why sympathetic effects spread widely. Postganglionic axons, thinly myelinated, return to the spinal nerves through grey rami communicantes or run directly to plexuses around the heart and other viscera.

Through these relays the ganglia carry the outflow behind the fight-or-flight response: faster heart rate, wider pupils, sweating and redistribution of blood. Clinically, the stellate ganglion can be blocked with local anaesthetic to treat some pain conditions of the upper limb, and neuroblastoma, a childhood tumour, may arise from sympathetic ganglion tissue.

Course and supply

Arises from

Develop from neural crest cells; receive preganglionic fibres from the lateral horn of spinal segments T1 to L2 through white rami communicantes.

Ends in

Send postganglionic fibres back to every spinal nerve through grey rami communicantes, and visceral branches to the cardiac, pulmonary and vascular plexuses; some fibres pass through unrelayed as splanchnic nerves.

Supplies

Relay stations for sympathetic outflow to sweat glands, blood vessels, hair muscles and the organs of the head, neck and chest, and a conduit for preganglionic fibres to the prevertebral ganglia of the abdomen and pelvis.