Neural Innervation of the GI Tract
The GI tract is regulated by an intrinsic set of nerves known as the Enteric Nervous System and by an extrinsic set of nerves that are part of the ANS.
Enteric Nervous System (ENS)
Called the “brain of the gut” the ENS consists of about 100 million neurons that extend from the esophagus to the anus.
Arranged into 2 plexuses:
1) Myenteric Plexus : located b/t the longitudinal and circular smooth muscle layers of the muscularis.
2) Submucosal Plexus : located within the submucosa.
The 2 plexuses consist of motor neurons, interneurons, and sensory neurons:
The motor neurons of the myenteric plexus supply the longitudinal and circular smooth muscle layers of the muscularis, so this plexus mostly controls GI tract motility, particularly the frequency and strength of contraction of the muscularis. Motor neurons of the submucosal plexus supply the secretory cells of the muscosal epithelium, controlling the secretions of the organs of the GI tract. The interneurons of the ENS interconnect the neurons of the myenteric and submucosal plexuses.
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