Splanchnic

Splanchnic is an anatomical term that denotes relationships to the viscera, the internal organs within the thoracic and abdominal cavities, especially the gastrointestinal tract, liver, spleen, and pancreas. The word derives from the Greek splankn, meaning entrails or viscera.

In anatomy and physiology, splanchnic is used to describe nerves, vessels, and regions that serve the visceral organs. The thoracic splanchnic nerves (greater, lesser, and least) carry sympathetic preganglionic fibers from the thoracic spinal cord to prevertebral ganglia such as the celiac, superior mesenteric, and aortorenal ganglia, with postganglionic fibers reaching abdominal viscera. The pelvic splanchnic nerves, by contrast, are parasympathetic fibers arising from S2–S4 that supply the hindgut and pelvic organs.

Splanchnic circulation refers to the blood flow to the abdominal viscera and their supporting structures. It is supplied principally by the celiac trunk, superior mesenteric artery, and inferior mesenteric artery. Venous drainage is via the portal venous system to the liver, forming the hepatic portal circulation. Because the viscera receive a large and variable portion of cardiac output, splanchnic blood flow changes with digestion, stress, and disease.

Clinical relevance includes the role of splanchnic nerves in visceral pain and autonomic regulation of abdominal organs. Procedures such as splanchnic nerve blocks can be used for pain management in certain abdominal conditions. The term also appears in radiology and anatomy to specify regions and structures associated with the viscera.