intricate layers of nervous tissue that control movements in the esophagus, stomach, and intestines. The mechanics of the nervous system's regulation of digestive functions is not fully known. Two major nerve centres are involved: the myenteric plexus (Auerbach's plexus) and the submucous plexus (Meissner's plexus). The myenteric plexus is situated between the circular muscle layer and the longitudinal muscle layer in the lower esophagus, stomach, and intestines. The submucous plexus, as its name implies, is located in the submucosal tissue, which connects the surface mucous membrane lining to the deeper muscle layers in the stomach and intestines.

The myenteric plexus receives its messages from the vagus nerve and responds by transmitting the message to muscle cells, which are thereby activated to contract. Control of nerve impulses is involuntary. The muscles of the stomach and intestines play an active role in digestion, as waves of muscle contractions (peristaltic waves) push food through the parts of the digestive tract. It is thought that the myenteric plexus stimulates the muscles to contract in peristaltic waves and that it helps keep muscle tone throughout the intestine walls, promotes secretions of intestinal juices, and allows muscular constrictions (sphincters) to open, thus permitting food to pass from one part of the digestive system to another.

The function of the submucous plexus is not as clearly defined. In the stomach its role may be partly inhibitory, working against the myenteric plexus to control the muscular contractions more finely. In the intestines it is generally believed to work in accord with the myenteric plexus in producing peristaltic waves and increasing digestive secretions.