Ulcers are crater-like sores (generally 1/4 inch to 3/4 inch in diameter, but sometimes 1 to 2 inches in diameter) which form in the lining of the stomach (called gastric ulcers), just below the stomach at the beginning of the small intestine in the duodenum (called duodenal ulcers) or less commonly in the esophagus (called esophageal ulcers).

In general, ulcers in the stomach and duodenum are referred to as peptic ulcers.

The stomach is a bag of muscle that crushes and mixes food with the...