Esophagus

The esophagus is a muscular tube which carries food and liquids from the throat to the stomach for digestion after it has been chewed and chemically softened in the mouth. Food is forced downward to the stomach (or upwards, if one is standing on his head) by powerful waves of muscle contractions passing through the walls of the esophagus. Because these contractions are so strong in the throat and the esophagus, we can swallow in any position -- even upside-down! If the food is bad, poison, or more than we can "stomach," it may travel back by the same force to be thrown out through the mouth, which is called vomiting. The esophagus has a ring of muscle at the top and at the bottom. These rings close or contract after the food passes through and enters the stomach, where there is an abundance of churning acid waiting to digest the food. If the bottom muscle weakens, stomach contents, along with the stomach acid, may return to the esophagus and cause an uncomfortable, burning sensation known as "heartburn", although it is not connected with the heart at all, but be careful next time you are forced to swallow your pride.