Which of the following best describes peristalsis?

• A. Voluntary muscle contraction
• B. Circular muscular waves moving contents forward
• C. Opening of the anal sphincter
• D. Stopping digestion

Answer: (B)

Peristalsis is an automatic, coordinated movement of the smooth muscle lining the digestive tract that pushes contents forward. It works in waves: a ring of circular muscle behind the bolus contracts to squeeze it along, while the segment ahead relaxes to allow forward movement. This process is not under conscious control; it’s regulated by the enteric nervous system and autonomic signals.

Opening the anal sphincter is related to defecation, not the propulsion of contents along the digestive tract, and stopping digestion isn’t what peristalsis does. The description that best fits peristalsis is circular muscle contractions that create waves moving contents forward.