Corpus: Lesser splanchnic nerve

The lesser splanchnic nerve is part of the autonomic nervous system, specifically from the thoracic portion of the sympathetic trunk. It is one of the visceral nerves, also known as the splanchnic nerves.

The lesser splanchnic nerve carries efferent, preganglionic sympathetic fibres and visceroafferent fibres from spinal cord segments T9 to T12. The exact segmental origins can vary slightly in different anatomical texts. The nerve fibres pass through the thoracic ganglia without synapsing.

The lesser splanchnic nerve travels through the diaphragm without forming any synapses, reaching the superior and inferior mesenteric ganglia. At these ganglia, the preganglionic fibres synapse with the second neuron and continue as postganglionic fibres in the superior and inferior mesenteric plexuses. These plexuses travel along the corresponding arteries to their target organs.

In some cases, the lesser splanchnic nerve gives off an independent branch, known as the ramus renalis, to the renal plexus. If no branch is given off, another nerve, known as the least splanchnic nerve, emerges from the 12th thoracic ganglion and connects to the renal plexus.