Retroperistalsis is the reverse of the involuntary
smooth musclecontractions of peristalsis. It usually occurs as a precursor to vomiting. Peristalsismoves food through the gastrointestinal tractfrom the esophagusin the direction of the anus.
Local irritation of the stomach, such as bacteria or food poisoning, activates the emetic center of the brain which in turn signals an imminent vomiting reflex, food moves in the opposite direction, often from the
duodenumof the small intestineinto the stomach.
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