The esophagus is a muscular tube that connects the back of your mouth (the throat) to your stomach. The length of the esophagus is about 8 inches that travels in your neck then chest before enetering your abdomen. It runs behind the trachea (windpipe) and the heart, and in front of the vertebral column (spine). The esophagus enters the abdominal cavity by passing through a small openning in the diaphragm (a sheet of muscle separating the chest and lungs from the abdomen) called the esophageal hiatus.
The esophagus is lined by moist pink tissue called mucosa which is thick and resembles your skin in some ways.
There are two valves at each end of the esophagus to keep closed at all time. The upper esophageal sphincter (UES) and the the lower esophageal sphincter (LES).