Stomach

The stomach acts as a reservoir for food and has a capacity of two and a half pints. Within the stomach, solid food material is churned and kneaded for about three hours until it becomes a semiliquid mass known as chyme. The chyme is then forced into the small intestine, where the process of digestion is completed. The wall of the stomach has three muscular layers, an outer longitudinal layer, a middle circular layer and an inner oblique layer. As the stomach fills with food, wavelike contractions of the wall begin, and as these waves move along the stomach wall some of the food is passed through the relaxed muscle valve at the base and into the duodenum, the first part of the small intestine, where it is further digested before being absorbed into the body