The esophagus is an organ in the digestive system. It is part of the gastrointestinal (GI) tract, which is the tube that goes from the mouth to the anus. The GI tract includes the esophagus, stomach, small intestine and large intestine. Other organs of the digestive system include the liver, gallbladder and pancreas.
The esophagus is a hollow, muscular tube that allows food to pass from the mouth to the stomach. It is 25–33 cm long and less than 2.5 cm cross at its narrowest part. The esophagus begins in the throat, or pharynx, and connects to the stomach. In the throat, it lies behind the windpipe, or trachea. In the chest cavity, it is in front of the backbone, or spine.
There are a number of lymph nodes in and around the esophagus. Lymph nodes are small bean-shaped masses of lymphatic tissue along lymph vessels (tubes through which lymph fluidlymph fluidA clear, yellowish fluid that contains nutrients, lymphocytes (a type of white blood cell that fights germs, foreign substances or cancer cells) and antibodies. Lymph fluid circulates throughout the body in lymph vessels and bathes body tissues. travels in the body). Lymph nodes store lymphocytes (a type of white blood cell that fights germs, foreign substances or cancer cells) and filter bacteria and foreign substances (including cancer cells) from lymph fluid.
Layers of the esophagus
The esophagus is made up of the following 3 layers of tissues and is covered by the adventitia.
The mucosa is the inner lining of the esophagus. It is made up of:
- a thin layer of squamous cells (called the epithelium)
- a layer of connective tissue (called the lamina propria)
- a thin layer of muscle (called the muscularis mucosa)
The submucosa is a layer of connective tissue that surrounds the mucosa layer. It contains mucous glands, blood vessels, nerves and lymphatic tissue.
The muscularis propria lies outside of the submucosa layer. It has an inner ring of circular muscle fibres and an outer ring of long muscle fibres that surround the wall of the esophagus.
The adventitia is a layer of connective tissue that loosely supports and covers the outside of the esophagus in the neck and chest.
Although the esophagus is part of the digestive system, it doesn’t actually play a role in digestion of food. But it is still an important organ in the GI tract.
When you swallow, the muscular walls of the esophagus tighten, or contract, to push food and fluids from the mouth into the stomach. Glands in the submucosa layer of the esophagus make mucus, which helps keep the inside of the esophagus moist and gives lubrication for swallowing.
The upper esophageal sphincter is a ring of muscle fibres. It detects food and liquids in the back of the throat. When you swallow, this sphincter closes allowing food to pass from the mouth into the esophagus and preventing food from going into the trachea.
The wall of the esophagus includes 2 layers of strong muscles. These muscles tighten, or contract, to help push food along until it reaches the stomach. The series of contractions that move food through the esophagus is called peristalsis.
There is another ring of muscle fibres at the bottom of the esophagus. These muscle fibres form the lower esophageal sphincter (also known as the cardiac sphincter). This sphincter prevents food from moving up out of the stomach. The area where the esophagus joins the stomach is called the gastroesophageal (GE) junction.
At the GE junction, the lower esophageal sphincter acts like a valve to control the passage of food into the stomach. When it opens, the valve lets food into the stomach. When closed, it prevents the stomach contents from going back into the esophagus.