<P> In early embryogenesis, the esophagus develops from the endodermal primitive gut tube . The ventral part of the embryo abuts the yolk sac . During the second week of embryological development, as the embryo grows, it begins to surround parts of the sac . The enveloped portions form the basis for the adult gastrointestinal tract . The sac is surrounded by a network of vitelline arteries . Over time, these arteries consolidate into the three main arteries that supply the developing gastrointestinal tract: the celiac artery, superior mesenteric artery, and inferior mesenteric artery . The areas supplied by these arteries are used to define the midgut, hindgut and foregut . </P> <P> The surrounded sac becomes the primitive gut . Sections of this gut begin to differentiate into the organs of the gastrointestinal tract, such as the esophagus, stomach, and intestines . The esophagus develops as part of the foregut tube . The innervation of the esophagus develops from the pharyngeal arches . </P> <P> Food is ingested through the mouth and when swallowed passes first into the pharynx and then into the esophagus . The esophagus is thus one of the first components of the digestive system and the gastrointestinal tract . After food passes through the esophagus, it enters the stomach . When food is being swallowed, the epiglottis moves backward to cover the larynx, preventing food from entering the trachea . At the same time, the upper esophageal sphincter relaxes, allowing a bolus of food to enter . Peristaltic contractions of the esophageal muscle push the food down the esophagus . These rhythmic contractions occur both as a reflex response to food that is in the mouth, and also as a response to the sensation of food within the esophagus itself . Along with peristalsis, the lower esophageal sphincter relaxes . </P> <P> The stomach produces gastric acid, a strongly acidic mixture consisting of hydrochloric acid (HCl) and potassium and sodium salts to enable food digestion . Constriction of the upper and lower esophageal sphincters help to prevent reflux (backflow) of gastric contents and acid into the esophagus, protecting the esophageal mucosa . In addition, the acute angle of His and the lower crura of the diaphragm helps this sphincteric action . </P>

The movement of food in food pipe is called