Which structure opens as the bolus traverses the thoracic esophagus?

Which structure opens as the bolus traverses the thoracic esophagus?

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

Answer: (A)

As the bolus moves toward the stomach, the gate at the gastroesophageal junction is what must open. That gate is the lower esophageal sphincter, specifically its abdominal portion, which lies just above the stomach. During swallowing, the distal esophagus and the abdominal part of the LES relax in a coordinated way so the bolus can pass into the stomach. The upper esophageal sphincter is at the top of the esophagus and opens at the start of swallowing; the pyloric sphincter controls outflow from the stomach to the duodenum; the diaphragmatic hiatus is just the opening through the diaphragm and isn’t the active gate for esophageal transit. The abdominal portion of the lower esophageal sphincter is the structure that opens to allow the bolus to enter the stomach as it traverses the thoracic esophagus.

As the bolus moves toward the stomach, the gate at the gastroesophageal junction is what must open. That gate is the lower esophageal sphincter, specifically its abdominal portion, which lies just above the stomach. During swallowing, the distal esophagus and the abdominal part of the LES relax in a coordinated way so the bolus can pass into the stomach. The upper esophageal sphincter is at the top of the esophagus and opens at the start of swallowing; the pyloric sphincter controls outflow from the stomach to the duodenum; the diaphragmatic hiatus is just the opening through the diaphragm and isn’t the active gate for esophageal transit. The abdominal portion of the lower esophageal sphincter is the structure that opens to allow the bolus to enter the stomach as it traverses the thoracic esophagus.