The plexus in the muscularis and nerves in the mucosa of the GI tract play important roles in the physiological functions of the tract. The plexus in the muscularis controls the contractions of the smooth muscle, while the nerves in the mucosa control the secretion of digestive juices and the absorption of nutrients. The muscularis plexus, also known as the myenteric plexus, regulates the peristaltic movements of the tract that move the food along the digestive system. On the other hand, the submucosal plexus controls the secretion of enzymes and hormones that aid in digestion and absorption of nutrients.
In Hirschsprung's disease, a congenital disorder of the colon, there is a defect in the myenteric plexus, which causes an absence of nerve cells in the affected area of the colon. This leads to a blockage of the colon, preventing stool from passing through. Symptoms of the disease include constipation, abdominal distension, and vomiting, among others. This highlights the importance of the myenteric plexus in regulating the contractions of the smooth muscle in the colon, as the absence of nerve cells in this area disrupts the normal physiological function of the GI tract.