The anatomy of the human stomach is shown in figure 1. The cardia surrounds the superior opening of the stomach. The rounded portion superior to the body and to the left of the cardia is the fundus. Inferior to the fundus is the large central portion of the stomach, called the body. The region of the stomach that connects to the duodenum is the pylorus. It has two parts, the pyloric antrum, which connects to the body of the stomach, and the pyloric canal, which leads into the duodenum. The pylorus communicates with the duodenum of the small intestine via the pyloric sphincter (valve). This valve regulates the passage of chyme from stomach to duodenum and it prevents backflow of chyme from duodenum to stomach (Tortora and Grabowski, 1996). The stomach wall is composed of four layers: mucosa, submucosa, muscularis and serosal (figure 2). 
Figure 1. External and internal anatomy of the stomach of man (Tortora and Grabowski, 1996).
Figure 2. Histology of the stomach. a three-dimensional view of layers of the stomach (Tortora and Grabowski, 1996). | 
