What is the process called where food is moved through the intestines by waves of rhythmic involuntary muscle contractions?

• A. Peristalsis
• B. Segmentation
• C. Sphincter action
• D. Emulsification

Answer: (A)

Peristalsis is the wave-like, coordinated contraction of smooth muscle along the gastrointestinal tract that pushes contents forward. In the intestines, these rhythmic contractions move chyme along the tract, propelling it from one section to the next. This movement is distinct from segmentation, which mainly mixes and churns the contents to aid digestion. Sphincter action refers to the opening and closing of valves that regulate flow between sections, not the general propulsion. Emulsification is the breakdown of fats by bile, a chemical process, not a movement mechanism.