splanhnicnärvid

Splanhnicnärvid, also known as splanchnic nerves, are a group of autonomic nerves that primarily innervate the abdominal viscera. These nerves originate from the sympathetic trunk and carry both sympathetic and parasympathetic fibers, although their sympathetic component is more prominent. The major splanchnic nerves are the greater, lesser, and least splanchnic nerves, which arise from specific thoracic spinal cord segments.

The greater splanchnic nerve, typically originating from thoracic segments T5-T9, is the largest. It passes through the diaphragm and synapses in the celiac ganglion, a major prevertebral ganglion. From the celiac ganglion, postganglionic fibers innervate organs such as the stomach, liver, gallbladder, spleen, pancreas, and parts of the small intestine. The lesser splanchnic nerve, arising from T10-T11, often synapses in the superior mesenteric ganglion and innervates parts of the small intestine and proximal large intestine. The least splanchnic nerve, usually from T12, may synapse in the inferior mesenteric ganglion, innervating distal parts of the large intestine, rectum, and pelvic organs.

These nerves play a crucial role in regulating various visceral functions, including digestion, absorption, blood flow to abdominal organs, and the sensation of visceral pain. They are integral to the "fight-or-flight" response, causing effects like decreased digestive activity and increased heart rate during stressful situations. Conversely, the parasympathetic components, carried via the vagus nerve, generally promote digestive processes. Understanding the splanchnic nerves is vital in the study of autonomic neurology and the diagnosis and treatment of gastrointestinal and abdominal disorders.