Ulcers - Definition

An ulcer is any break in the skin or in a mucous membrane. Mucous membrane is a thin tissue that lines the interior surface of body openings. The term ulcer is used most commonly to refer to ulcers that occur in the upper part of the digestive system, such as peptic ulcers. At one time, doctors believed that ulcers were caused by too much stress. However, it is now known that bacterial infection accounts for more than three-quarters of all peptic ulcers.