What describes involuntary waves of muscle contraction that move food in one direction through the digestive system?

• A. Peristalsis
• B. Segmentation
• C. Absorption
• D. Digestion

Answer: (A)

Movement of food through the digestive tract via waves of muscle contraction is called peristalsis. These coordinated contractions of the smooth muscle in the GI wall create a traveling wave that pushes contents forward, from the esophagus toward the stomach and along the intestines, in one direction and without reversing. Segmentation mixes and chops the contents to improve enzyme contact and absorption, rather than pushing it forward. Digestion refers to breaking down food, and absorption is the uptake of nutrients after digestion. So the described one-directional propulsion of food is peristalsis.