Esophagus

          Esophagus is derived from the Greek word 'oisophagus', 'oisein' meaning to carry and 'phagein', to eat. It is also called the swallowing tube or gullet. The length of the esophagus in a normal adult is 10 inches (25 centimeters approx). The esophagus location is between the windpipe (trachea) and the spine. It opens in the mouth and passes down the neck till the diaphragm, joining the upper end of the stomach. There are a number of glands lining the inner wall of the esophagus that help in keeping the passage moist and also facilitate in swallowing.

          The esophagus is a muscular tube connecting the throat (pharynx) with the stomach. The esophagus is about 8 inches long, and is lined by moist pink tissue called mucosa. The esophagus runs behind the windpipe (trachea) and heart, and in front of the spine. Just before entering the stomach, the esophagus passes through the diaphragm.

          The upper esophageal sphincter (UES) is a bundle of muscles at the top of the esophagus. The muscles of the UES are under conscious control, used when breathing, eating, belching, and vomiting. They keep food and secretions from going down the windpipe.

          The lower esophageal sphincter (LES) is a bundle of muscles at the low end of the esophagus, where it meets the stomach. When the LES is closed, it prevents acid and stomach contents from traveling backwards from the stomach. The LES muscles are not under voluntary control.

FUNCTION:


          The esophagus is a vital part of the digestive system and plays a major role in transporting food, saliva and liquids to the stomach. The main esophagus function is to transport food from the mouth to the stomach. This esophagus function is carried out by a layer of muscles, lining the wall of the esophagus, called sphincters. The food in the esophagus is transported to the stomach by a series of contractions caused by sphincters. Food in the mouth is carried to the esophagus by peristalsis, a process where muscles contract to push food through the esophagus to the stomach. When this esophagus function occurs, the muscles or sphincters automatically close in order to stop food from returning to the mouth or esophagus. Apart from this esophagus function, sphincters also release certain enzymes that help in the semi digestion of food in the esophagus. Even if the person is lying down or is upside down, sphincters enable the food to be pushed into the stomach. There are two parts of the sphincters, the upper esophageal sphincter and lower esophageal sphincter. The upper sphincter is usually closed, but opens when food or liquid is swallowed. The passage to the lungs is blocked when the upper sphincter is open, in order to prevent food or liquid from entering the lungs. The esophagus is connected to the stomach by the lower esophageal sphincter. The lower sphincter of esophagus remains closed even at rest, thus preventing the contents from flowing back into the esophagus. When food is swallowed, upper esophageal sphincter relaxes to push the food into the upper esophagus. Food is further pushed into the lower esophagus by peristalsis. When food reaches the bottom of the esophagus, lower esophageal sphincter loosens up to transport food into the stomach.