What is the purpose of peristalsis?

• A. To move food through the digestive tract
• B. To absorb nutrients in the small intestine
• C. To break down fats
• D. To neutralize stomach acid

Answer: (A)

Wave-like contractions of smooth muscle push contents along the digestive tract. Peristaltic waves coordinate constriction of circular muscle behind the bolus with shortening of the longitudinal muscle ahead, creating a forward push that moves food from the esophagus through the stomach and into the intestines. This propulsion is driven by the enteric nervous system and modulated by autonomic input, so movement occurs even without conscious control. The purpose is to transport material to sites of digestion and absorption downstream. Absorption happens mainly in the small intestine, fats are digested enzymatically with bile, and stomach acid is neutralized chemically in the duodenum—these are separate processes from peristaltic propulsion.