Where does segmentation mainly occur, and which muscle produces it?

1. Segmentation is a mixing movement rather than a movement that drives food forward. 2. It occurs mainly in the small intestine and consists of localized contractions of circular muscle. 3. These contractions isolate short sections, moving the contents back and forth so they mix with digestive juices. 4. The stomach mixes food with mixing waves that use its extra oblique layer, which is a different movement. 5. The esophagus uses peristalsis to push a bolus onward, so it is not the seat of segmentation. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 23 "The Digestive System", section 23.2 Digestive System Processes and Regulation_