The upper gastrointestinal tract is the part of the digestive system that starts from the mouth and extends to the stomach. It is responsible for the intake of food, breaking it down into smaller particles, and providing essential nutrients to the body. Diseases of the upper gastrointestinal tract include: gastroesophageal reflux disease, peptic ulcer disease, gastritis, and esophageal cancer. Gastroesophageal reflux disease (GERD) is a condition where stomach acid flows back up into the esophagus and causes a burning sensation in the chest. It is caused by a weakened or malfunctioning lower esophageal sphincter. Symptoms include heartburn, regurgitation, and chest pain. Treatment includes lifestyle changes, medications, and in some cases, surgery. Peptic ulcer disease is caused by the inflammation of the lining of the stomach or small intestine due to the presence of a bacterial infection. Symptoms may include abdominal pain, bloating, nausea, and vomiting. Treatment includes antibiotics and medications that decrease the amount of acid in the stomach. Gastritis is an inflammation of the stomach lining caused by infection, irritation, or stress.