The stomach is a hollow muscular organ of the digestive system that is designed to accumulate and digest food. It is positioned in the abdominal cavity inferior to the left dome of the diaphragm and lies between the esophagus and the duodenum. Overall, it provides mechanical and chemical food digestion, a small degree of absorption and secretion of various hormones and substances.

Because of its muscular structure, the stomach is an expandable organ representing the most dilated part of the gastrointestinal tract. Also, it connects the upper gastrointestinal tract with the lower. 

The stomach is a direct continuation of the abdominal esophagus, which extends between the esophageal hiatus of the diaphragm (at the level of the T10 vertebra) and the cardiac orifice of the stomach (at the level of the T11 vertebra). The junction site between the stomach and the esophagus is called the gastroesophageal junction. 

The stomach ends at the pyloric opening (at the level of the first lumbar vertebra (L1)) and continues as the duodenum. Overall, the stomach is relatively fixed at its esophageal and pyloric ends. 

The stomach appears J-shaped and has two curvatures that limit its two surfaces. Additionally, the stomach is composed of four parts.