Innervation

Parasympathetic innervation of the gut promotes peristalsis while it’s sympathetic innervation promotes vasoconstriction and inhibits peristalsis and digestion.

The enteric nervous system is the neuronal circuitry of the gastrointestinal wall and consists of the following:

  1. Meissner’s plexus in the submucosa

  2. Myenteric (Auerbach’s) plexus between the muscularis externa layers


Parasympathetic Innervation

  1. The anterior and posterior vagal trunks are continuations of the right and left vagus nerves that emerge from the esophageal plexus. The anterior and posterior vagal trunks innervate foregut and midgut structures.

  2. Pelvic splanchnic nerves are derived directly from the anterior rami of S2-S4 spinal nerves

Sympathetic Innervation

  1. Splanchnic nerves include:

    • Greater splanchnic nerves (T5-T9) - celiac ganglia

    • Lesser splanchnic nerves (T10-T11) - superior mesenteric ganglia

    • Least splanchnic nerves (T12) - aorticorenal ganglia

    • Lumber splanchnic nerves (L1-L2/3) - inferior mesenteric and superior hypogastric plexus

Pain Afferents

  1. Accompany sympathetic innervation:

    • Foregut T6-T9 - epigastric dermatome

    • Midgut T8-T12 - umbilical dermatome

    • Hindgut T12-L2 - hypogastric dermatome