This dark intimidating tunnel is called an esophagus, which one of our more intelligent secret agents found out. My travel down the esophagus will be helped by the contracting muscles (peristalsis), and I will then be pushed down the opening of the stomach (sphincter) that we know to be a sphincter. The huge cavern (stomach) is known to be a stomach. It will churn me around as I will be broken down by yet another liquid (hydrochloric acid/ gastric juices). I will leave the stomach then and enter a very long tube (small intestine) that is the small intestine.