[2][3] A part of the enteric nervous system, the myenteric plexus exists between the longitudinal and circular layers of muscularis externa in the gastrointestinal tract.

The myenteric plexus originates in the medulla oblongata as a collection of neurons from the ventral part of the brain stem.

The events that are controlled, at least in part, by the ENS are multiple and include motor activity, secretion, absorption, blood flow, and interaction with other organs such as the gallbladder or pancreas.

[7] The heavily studied neuropeptide known as substance P is present in significant levels and may help facilitate the production of saliva, smooth muscle contractions, and other tissue responses.

[10] Achalasia is a motor disorder of the esophagus characterized by decrease in ganglion cell density in the myenteric plexus.

[11] Myenteric plexi destruction has been found to be secondary to Chagas disease (T. cruzi infection sequelae).

This denervation can lead to secondary achalasia (lower esophageal sphincter will not open; loss of inhibitory neurons), megacolon, and megaureter, respectively.

[12] PD patients are known to experience severe constipation due to GI tract dysfunction years before the onset of motor movement complications, which characterises Parkinson's disease.