What is the sympathetic innervation source for the ileum?

The ileum, which is the final part of the small intestine, receives its sympathetic innervation primarily from the lesser splanchnic nerve. This nerve emerges from the sympathetic trunk and contributes fibers that synapse in the superior mesenteric ganglion. From there, postganglionic fibers extend to the ileum and various parts of the intestines. The function of sympathetic innervation in this region generally includes the reduction of intestinal motility and the inhibition of secretions, thereby regulating the digestive process.

The greater splanchnic nerve primarily supplies sympathetic innervation to the upper abdominal viscera, while the lesser splanchnic nerve can target the kidneys and proximal ureters, making them less relevant for the ileum specifically. The celiac plexus mainly serves the foregut structures including the stomach and parts of the pancreas and liver, and is not the direct source for the ileum's sympathetic supply. Understanding which nerves specifically target the ileum is essential for comprehending the overall sympathetic nervous system's role in gastrointestinal functionality.