The stomach is located between the esophagus and small intestine. It is J-shaped with three parts: the fundus, body, and antrum. The stomach contains two sphincters that control emptying into the small intestine. Its functions include storing food, churning it into chyme through contractions and enzymes, and slowly emptying into the small intestine. The stomach lining absorbs water, medications, amino acids, alcohol, and caffeine. Common stomach problems include GERD, gastritis, and peptic ulcers.