Peptic ulcer. Light micrograph of a cross section of the lower oesophagus showing ulceration. The peptic ulcer is at centre. The oesophagus or gullet forms the part of the alimentary canal that runs from the back of the throat to the stomach. An ulcer is an inflamed eroded area of the protective layer of organs and tissue. The wall of the surface mucous membrane has been damaged, causing the underlying cells to be destroyed by acidic gastric juices. Causes of gastric ulcers are related to diet, alcohol consumption, stress and certain drugs. Symptoms are alleviated by antacid medicines, but severe cases may require surgery. Magnification unknown.