The food bolus is transported by gravity and by peristaltic propulsion, depending on its consistency and the position of the subject. Reflex constriction of the upper oesophageal sphincter takes place.
Primary peristaltic waves propel the bolus distally. Secondary peristalsis may be initiated by oesophageal distension due to food remnants within the oesophagus if primary peristalsis is insufficient to allow oesophageal clearance. Tertiary contractions may also occur. The lower oesophageal sphincter relaxes.
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