The esophagus is an organ of the digestive tract. It connects the pharynx in the neck to the stomach in the abdomen. The role of the esophagus is to transport solid and liquid food to the stomach. The esophagus is made up of 3 segments: the cervical esophagus directly connected to the pharynx, the thoracic esophagus which crosses the diaphragm and the abdominal esophagus which leads to the stomach. At each end of the esophagus there is a sphincter, the upper and lower sphincter. The lower sphincter controls the passage of food into the stomach and prevents reflux from the stomach. Like the stomach, the esophageal wall is made up of four layers of tissue: the mucosa, which is a non-keratinized malphigian epithelium, the submucosa, which is a denser connective tissue and contains vessels and nerves, the muscularis, and the serosa or adventitia, which is loose connective tissue. The squamous epithelium of the mucosa protects against the abrasive effect of the food bolus as it passes through. It protects the underlying tissues and provides mechanical protection.