What is the involuntary wave-like contraction of smooth muscles in the digestive tract called?

The involuntary wave-like contraction of smooth muscles in the digestive tract is known as peristalsis. This process is essential for moving food along the digestive system, beginning in the esophagus and continuing through the stomach and intestines. Peristalsis involves alternating contractions and relaxations of smooth muscle layers that create a rhythmic motion, effectively pushing the contents forward.

Other terms in the options relate to different aspects of digestion. Digestion refers to the chemical breakdown of food into smaller components that can be absorbed, but it does not specifically describe the muscular contractions involved. Absorption is the process where the nutrients from digested food are taken into the bloodstream or lymphatic system, not the movement through the digestive tract. Segmentation also involves contractions of the digestive tract; however, it specifically refers to a back-and-forth mixing action rather than the forward-moving peristaltic waves. Thus, peristalsis is the correct term for the wave-like contractions that propel contents through the digestive system.