Innervation of the small intestine
Completing this study unit will allow you to:
- Name the nervous structures involved in the sympathetic and parasympathetic innervation of the small intestine.
- Define the main constituents of the enteric nervous system.
- Describe the functions of the intrinsic and extrinsic innervation of the small intestine.
The small intestine has an extrinsic and intrinsic innervation. The extrinsic innervation is facilitated via the sympathetic and parasympathetic divisions of the autonomic nervous system, the intrinsic innervation via the enteric nervous system.
Preganglionic sympathetic fibers from the thoracolumbar spinal cord travel as the greater and lesser thoracic splanchnic nerves to the celiac, aorticorenal and superior mesenteric ganglia. From there, postganglionic fibers are distributed via the celiac/superior mesenteric plexus to the duodenum, jejunum and ileum to inhibit digestion. Both the anterior and posterior vagal trunks of the vagus nerve send preganglionic parasympathetic contributions via the celiac ganglia which then follow the same pathway as the sympathetic fibers to stimulate digestion. Postganglionic parasympathetic fibers are located in the target organ wall.
The enteric nervous system regulates muscle tone and contractions, nutrient absorption and enzyme secretion via the myenteric plexus (plexus of Auerbach) and the submucosal plexus (Meissner's plexus).
Learn about the innervation of the small intestine in our video!
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Explore each of the neural structures you have learned about in the gallery below.
Preganglionic: Greater and lesser thoracic splanchnic nerves from thoracolumbar spinal cord to celiac, aorticorenal and superior mesenteric ganglia
Postganglionic: Fibers from celiac and superior mesenteric ganglia to small intestine
Function: Inhibits digestion
Preganglionic: Anterior and posterior vagal trunk to intestinal wall (passing via celiac and superior mesenteric plexus, without synapsing)
Postganglionic: Located in intestinal wall
Function: Stimulates digestion
Myenteric plexus (of Auerbach): Regulates smooth muscle tone and contractions
Submucosal plexus (Meissner's Plexus): Regulates intestinal enzyme secretion, food absorption and (sub)mucosal muscle movement
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