Oral Phase of Swallowing Swallowing is under voluntary control in the mouth Propels the food bolus from the mouth to the pharynx tongue forces the food bolus back towards the pharynx activates the somatosensory receptors located near the pharynx initiates involuntary swallowing reflex in the swallowing center in the medulla Pharyngeal Phase of Swallowing Swallowing is under involuntary ("reflex") control in the pharynx Propels the food bolus from the pharynx to the esophagus soft palate rises to prevent the food bolus from entering the nasopharynx epiglottis covers the laryngeal opening to prevent the food bolus from entering the trachea upper esophageal sphincter relaxes and opens allows the food bolus to move from the pharynx to the esophagus a peristaltic wave of contraction mediated by the swallowing reflex initiates in the pharynx and propels the food bolus from the pharynx, through the upper esophageal sphincter, into the esophagus Breathing is inhibited during the pharyngeal phase of swallowing Esophageal Phase of Swallowing Swallowing is under involuntary ("reflex") control in the esophagus Propels the food bolus from the esophagus to the stomach food bolus is propelled from the pharynx, through the upper esophageal sphincter, and into the esophagus once the food bolus enters the esophagus, the upper esophageal sphincter contracts and closes to prevent the food bolus refluxing into the pharynx a primary peristaltic wave of contraction mediated by the swallowing reflex involving a series of coordinated, sequential contractions propels the food bolus from the esophagus, through the cardiac sphincter (lower esophageal sphincter), and into the stomach if the primary peristaltic wave of contraction does not clear the esophagus of food, a secondary peristaltic wave mediated by the enteric nervous system is initiated