Which term is used for the mixing movements of the small intestine?

• A. Peristaltic waves
• B. Migrating motor complex
• C. Gastrointestinal reflexes
• D. The segmental contractions

Answer: (D)

Segmental contractions, or segmentation, are the mixing movements of the small intestine. These are rhythmic contractions of the circular smooth muscle that occur in alternating segments, constricting and then relaxing, which churns the chyme and moves it back and forth between sections. This mixing increases contact with the absorptive surface and exposes the chyme to digestive enzymes, promoting digestion and absorption. They are driven by the intestinal pacemaker activity and occur continually, focusing on mixing rather than propelling contents forward. In contrast, peristaltic waves push contents along the tract, the migrating motor complex sweeps residual material during fasting, and gastrointestinal reflexes describe various neural reflexes that regulate gut function.