Esophagus or esophagus - is part of the gastrointestinal tract, located between the pharynx and stomach. It starts with the esophagus in the neck at the level of the fourth cervical vertebra, descends into the chest cavity along the spine, passes through the esophageal opening, penetrating into the cavity of the abdomen, and empties into the upper part of the stomach called the cardiac side.
Next to the thoracic esophagus is part of the aorta and trachea. The wall of the esophagus consists of three layers. The inner layer - lining it, under it is a loose submucosal layer, then the muscular layer, consisting of a ring-shaped muscle fibers and the outer sheath of connective tissue cells, which during the transition into the abdominal cavity is called the serosa.
In the course of the esophagus, there are three restrictions: on the level of origin of the esophagus from the pharynx at the level of the fourth thoracic vertebra and at the junction of the esophagus through the diaphragm.
In the esophagus, there are two sphincter muscles - sphincter muscle - at the entrance to the esophagus and the transition of the esophagus to the stomach. The main function of the esophagus - Delivery of food from the pharynx to the stomach. Food, crushed and moistened with saliva in the mouth, moves to the root of the tongue. This process can control the people arbitrarily.
Then there is irritation of the nerve receptors of the tongue, pharynx, soft palate, and swallowing reflex occurs as a result of which with the help of coordinated movements of the muscles of the pharynx, the bolus is pushed into the esophagus. The soft palate at the same time blocks the entrance to the nasal cavity and the epiglottis closes the entrance to the trachea. Food, thus, can be reached only into the esophagus.
The upper esophageal sphincter contracts to prevent the return of the food back. Next, the bolus is slowly moving down the esophagus under the influence of differential pressure, gravity and consistent muscle contractions of the esophagus wall, the so-called peristaltic waves. At the entrance to the stomach is the second esophageal sphincter, which is normally closed position, but his approach to food bolus and peristaltic wave, it opens and food enters the stomach.