After being pushed through the upper esophageal sphincter, you come to the long passageway called the esophagus. (To see the entire esophagus, click on the word, "Esophagus," above.) Being quite muscular, the esophagus is able to push a bolus towards the stomach by peristalsis. Peristalsis is the succession of muscular contractions along a hollow muscular structure. The esophagus squeezes a bolus through its tube with its muscles just like toothpaste is squeezed through the tube with your hand. As you exit the long passageway, you come across another sphincter, the lower esophageal sphincter. What's that you see ahead? Could it be the stomach's rugae?
