Movement of the bolus through the thoracic esophagus forces what to open?

• A. Lower esophageal sphincter abdominal portion
• B. Upper esophageal sphincter
• C. Pyloric sphincter
• D. Esophageal hiatus

Answer: (A)

As the bolus travels down the thoracic esophagus, it ultimately reaches the gastroesophageal junction and needs to enter the stomach. This requires the lower esophageal sphincter to relax and open. The abdominal portion of the lower esophageal sphincter forms the barrier at the junction and must open to permit passage into the stomach. The upper esophageal sphincter is the gate at the top of the esophagus and opens to allow entry of the bolus into the esophagus, not for its transit into the stomach. The pyloric sphincter sits at the exit of the stomach into the duodenum and is not involved in moving the bolus from the esophagus. The esophageal hiatus is the diaphragmatic opening the esophagus passes through and does not actively open to let the bolus through.