Anatomy
Jan S. Suchodolski
The stomach can be divided into a proximal and a distal portion. The proximal portion can be further divided into three regions: cardia, fundus, and body (Figure 4.1).
The cardia is the thin portion of the stomach that is connected to the intraabdominal portion of the esophagus. The fundus, which often contains gas that can be seen on abdominal radiographs, follows the cardia, and is located on the left side of the stomach. The corpus is the largest portion of the stomach and connects fundus and pylorus. Gastric fundus and corpus have the ability to dilate in order to accommodate a meal, while maintaining constant intragastric pressure. The proximal portion of the stomach is responsible for the production of most of the gastric juice. The distal portion of the stomach consists of the pyloric antrum, the pyloric canal, and a double sphincter, the pylorus. However, all three areas are often referred to as the pylorus. The major function of the distal portion of the stomach is to grind food particles and to aid in gastric emptying.The mucosa and the submucosa of the empty stomach are thrown into folds. The mucosal surface is stippled with numerous tiny openings, the gastric pits.
The stomach has three muscular layers: a longitudinal layer (absent in the cranial and caudal portions of the stomach); a circular layer, which is the predominant layer and present in all areas; and an oblique layer. The latter layer is the least developed. The activity of these muscle layers aids in gastric emptying. The pylorus is characterized by a thickening of the circular muscle layer of the distal antrum.
4.3