Explain how small intestine motility differs during fasting and eating

Question

What will be an ideal response?

Answer 1

Small intestinal motility differs during fasting and eating. During fasting, the small intestine exhibits slow, rhythmic contractions along its length in a pattern called the migrating motor complex. These contractions clear any remaining material from the small intestine, including leftover food and secretions. The migrating motor complex requires about 2 hours to push digesting food from the duodenum to the ileocecal valve. This movement is controlled by both the enteric nervous system (ENS) and a hormone called motilin, which is produced by cells in the duodenal mucosa. The small intestine undergoes two types of movement during eating: peristalsis and segmentation. As with other regions of the alimentary canal, peristalsis in the small intestine is accomplished by alternating contractions of the longitudinal and circular layers of smooth muscle in the muscularis externa. Its primary function is to propel chyme toward the ileum and ultimately through the ileocecal valve to the cecum. However, segmentation, also known as intestinal churning, involves contractions of only the circular layer of smooth muscle, which produces a squeezing motion. The primary functions of segmentation are mechanical digestion and mixing the chyme with intestinal and pancreatic enzymes as well as bile. The vagus nerve appears to regulate both peristalsis and segmentation.