The esophagus (oesophagus) is a muscular tube which links the throat to the stomach. It lies behind the trachea (throat) and heart, and in front of the spinal column. It passes through the muscular chest diaphragm before reaching the stomach. The function of the esophagus is to propel food from the back of your throat to your stomach. It can contract or expand to allow for the passage of food.
The esophagus is about 10 inches in length. Each end of it is closed off by a ring of muscle (sphincter). At the top end, is the upper esophageal sphincter (UES), while at the bottom is the lower esophageal sphincter (LES), also known as the gastroesophageal junction, cardiac valve, or cardia. Usually, the UES remains closed. However, when food enters the back of the throat the spincter muscle relaxes and opens, allowing the food to enter the esophagus. The UES then closes to prevent regurgitation into the throat. The esophagus is lined with a protective mucous membrane and its walls are lined with muscles that slowly squeeze the food through the esophageal passage – a process known as peristalsis. When food reaches the end of the esophagus, the LES opens to allow food to pass through into the stomach, then closes to stop food or acidic gastric juice from the stomach from backing up. If either of these sphincters malfunctions, it can lead to a variety of digestive or gastric conditions, including achalasia, heartburn and gastroesophageal reflux disease (GERD). It takes about 2-3 seconds for food to pass through the esophagus and enter the stomach.