The stomach is a muscular organ that is part of the gastrointestinal (GI) tract and is responsible for digesting food. When food enters the stomach, it contracts and produces acids and enzymes that break down the food into smaller pieces. The stomach mixes the food with digestive juices, and the resulting mixture is called chyme. The stomach then passes the chyme to the small intestine, where further digestion and absorption of nutrients occur. The stomach has five distinct sections: the cardia, fundus, body, antrum, and pylorus. The stomachs size varies from person to person and can expand when full and deflate when empty. The stomachs primary function is to digest food and send it to the small intestine, and it has three functions: mechanical digestion, chemical digestion, and production of intrinsic factor. The stomachs muscular walls, acid production, and enzymes break down food into smaller pieces. The stomach absorbs only water, alcohol, and some drugs.