Esophagus

What is the Esophagus?

The esophagus is a hollow muscular tube (about 25 cm. long in an adult) that propels food in the form of a bolus to the stomach.

Where is the esophagus situated?
In the neck, the esophagus begins where the pharynx ends and extends to the stomach. It lies beneath the trachea or windpipe and above the vertebrae. In the chest, the esophagus lies beneath the left bronchus, which is a division of the trachea and is above the vertebrae and a large blood vessel called the descending aorta.

How can we describe the esophagus?
As we said, the esophagus is a hollow muscular tube. It is flat when empty but stretches when food passes through it. It is curved at three places in the chest and also has a total of four places where the tube is narrow. The esophagus has four coats. From inside out these are:

• Mucosa : This is the smooth layer of mucus membrane lining the inside of the esophagus. It is made of flat, tough and smooth cells.
• Submucosa : This lies below the mucosa and provides it with stability.
• Muscular coat : This again has a layer of circular muscle covered by a layer of lengthwise-arranged muscle.
• Fibrous Coat : This is a tough coat to provide shape and form to the esophagus. It also acts as a protective covering.

The muscle layer at the junction of the esophagus and stomach is thickened and has a sphincter like action. This action prevents the ingested food to be brought back up to the esophagus. It also prevents the stomach acids from coming up into the esophagus and thus preventing acidity.

Functions of the Esophagus

The main function of the esophagus is to transport food material from the mouth to the esophagus. Food takes two to three seconds to travel through the esophagus. Once the food is inside the esophagus it is squeezed through it by regular and alternate tightening and relaxation of the esophageal muscles. This squeezing action produces a wave like motion called as peristalsis, which propels the food down into the stomach. The sphincter at the end of the esophagus relaxes to let food pass into the stomach and tightens to prevent regurgitation or re-entry of food back into the esophagus.