The abdominal viscera are innervated, as all viscera are, by the autonomic nervous system. The parasympathetic innervation is delivered by the vagus primarily, with help from the pelvic splanchnic nerves. The sympathetic innervation comes primarily from the thoracic splanchnic nerves, greater, lesser, and least, with help from the upper lumbar splanchnic nerves.
Generally, parasympathetic innervation results in digestion, by stimulating peristalsis in the gut and secretion by associated glands. Sympathetic innervation, on the other hand, decreases blood flow to the abdominal viscera and inhibits digestion. Blood flow is diverted to the trunk and limbs, to aid the body in "fight or flight".
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