Peristalsis is
- A. a wave of contraction of circular muscle behind the food that pushes it along the gut
- B. the churning of food by the teeth
- C. the return of food from the stomach to the mouth
- D. the absorption of nutrients into the blood
Explanation
Circular muscle contracts behind the bolus and longitudinal muscle contracts in front of it, so a wave of narrowing travels along the tube and moves the contents in one direction. Because the muscle does the work, food reaches the stomach even when a person is lying down or standing on their head. The same mechanism moves material through the whole alimentary canal.
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