# Peristalsis --- **Peristalsis** is the wave-like, involuntary contractions of [[smooth muscle]] of a tube or duct that propels the contents forward. It is used extensively in the [[gastrointestinal tract|GI tract]] during [[digestion#Propulsion|digestion]], but also seen in places like the [[testes|vas deferens]]. ## Migrating Motility Complex The **migrating motility complex** is a special kind of peristalsis in the [[small intestine]]. It's a coordinated series of peristaltic waves that travel down the whole length of the small intestine to where it enters into the large intestine. Each individual wave travels about 2 feet, and the cumulative migrating motility complex takes about 2 hours to reach the end. ## Problems with Peristalsis - [[Achalasia]] is a failure of peristalsis in the esophagus which leads to a problem where the food can't enter the stomach. ___