The function of the esophagus is carry food and liquids from the mouth to the stomach. The esophagus is a muscular tube connecting from the throat, passing through a hole in the diaphragm, and connecting to the stomach. It is approximately 10 inches (25 cm) long.
When you swallow food, it doesn't just drop down into your stomach. Muscles contract in a wave-like motion to move the food along through the esophagus. This muscle movement is called, peristalsis, or peristaltic waves. These peristaltic waves contract behind the food bolus pushing it along the digestive tract. Mucous membrane in the esophagus produce mucus to lubricate the food bolis and help it move along the digestive tract.
The esophagus connects to the stomach at the lower esophageal sphincter, also called the cardia. The stomach has strong acids and enzymes, to aid in food digestion, that could be harmful to the esophagus. The lower esophageal sphincter prevents food and acids from returning up into the esophagus. Occasionally, food and acids do flow backward into the esophagus. This can cause a burning feeling in the chest, called heartburn or acid reflux.