Editing Peristalsis (section)

===Esophagus===

After food is chewed into a bolus, it is [[swallowing|swallowed]] and moved through the esophagus. Smooth muscles contract behind the bolus to prevent it from being squeezed back into the mouth. Then rhythmic, unidirectional waves of contractions work to rapidly force the food into the stomach. The [[migrating motor complex]] (MMC) helps trigger peristaltic waves. This process works in one direction only, and its sole esophageal function is to move food from the mouth into the stomach (the MMC also functions to clear out remaining food in the stomach to the small bowel and remaining particles in the small bowel into the colon).<ref name="ReferenceA"/>

[[Image:Peristalsis.gif|thumb|right|A simplified image showing peristalsis]]
In the esophagus, two types of peristalsis occur:
* First, there is a '''primary peristaltic wave''', which occurs when the bolus enters the esophagus during [[swallowing]]. The primary peristaltic wave forces the bolus down the esophagus and into the stomach in a wave lasting about 8–9 seconds. The wave travels down to the stomach even if the bolus of food descends at a greater rate than the wave itself, and continues even if for some reason the bolus gets stuck further up the esophagus.
* If the bolus gets stuck or moves slower than the primary peristaltic wave (as can happen when it is poorly lubricated), then stretch receptors in the esophageal lining are stimulated and a local reflex response causes a '''secondary peristaltic wave''' around the bolus, forcing it further down the esophagus, and these secondary waves continue indefinitely until the bolus enters the stomach. The process of peristalsis is controlled by the medulla oblongata. Esophageal peristalsis is typically assessed by performing an [[esophageal motility study]].
* A third type of peristalsis, tertiary peristalsis, is dysfunctional and involves irregular, diffuse, simultaneous contractions. These contractions are suspect in esophageal dysmotility and present on a barium swallow as a "[[corkscrew esophagus]]".<ref>{{Cite book |url=https://www.ncbi.nlm.nih.gov/books/NBK54271/|title=Motor Patterns of the Esophagus – Aboral and Oral Transport|last=Mittal|first=Ravinder K.|date=2011|publisher=Morgan & Claypool Life Sciences|language=en}}</ref>

During [[vomiting]], the propulsion of food up the esophagus and out the mouth comes from the contraction of the [[abdominal muscles]]; peristalsis does not reverse in the esophagus.{{cn|date=July 2022}}