splanchnicnerver

The splanchnic nerves are a group of thoracic nerves that carry preganglionic sympathetic fibers from the thoracic sympathetic trunk to prevertebral ganglia in the abdomen. They do not synapse in the sympathetic trunk; instead, preganglionic fibers pass to abdominal ganglia where they typically synapse in the celiac ganglion, the superior mesenteric ganglion, or the aorticorenal ganglia before continuing as postganglionic fibers to the abdominal viscera.

The main components are the greater, lesser, and least splanchnic nerves. The greater splanchnic nerve arises from the fifth to ninth thoracic spinal ganglia (T5–T9), the lesser from T10–T11, and the least from T12. After descending in the thorax, these nerves pass through the crura of the diaphragm to reach the abdomen. The greater splanchnic nerve primarily targets the celiac ganglion, while the lesser and least tend to synapse in the aorticorenal plexus, with fibers reaching the foregut, midgut, and, to varying extents, hindgut structures via their vascular and visceral branches.

Functionally, splanchnic nerves provide sympathetic innervation to abdominal viscera, influencing vascular tone, and modulating gastrointestinal secretions and motility. Visceral afferent fibers accompanying these nerves convey pain and reflex information back to spinal levels, contributing to referred pain from abdominal organs.

Clinical relevance includes pain patterns related to foregut and midgut organs, as well as the use of thoracic splanchnic nerve blocks in certain pain management and surgical contexts. Etymologically, “splanchnic” derives from a term related to the viscera.