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The stomach is a dilated portion of the digestive tract and has three main functions: storage of food, mixing of food with gastric secretions to form chyme, and control of chyme delivery rate to the small intestine so that efficient digestion and absorption can occur. The stomach is relatively fixed at both ends, but is very mobile in between. Anatomic segments are desribed as follows:
Cardia: The cardiac orifice is the first anatomical segment of the stomach and is denoted where the abdominal part of the esophagus enters the stomach. The cardia is a histologically defined region.
Fundus: The fundus is dome-shaped and directly adjacent to the cardia, projecting superiorly. It is typically air-filled and is the portion of the stomach where the gastric bubble is commonly appreciated on upright plain films.
Body: The body lies inferior to the fundus and extends from the cardiac orifice to the level of the incisura angularis, a notch in the lower part of the lesser curvature. The body represents the largest gastric segment; the shape and size of which is quite variable due to parastalsis.
Antrum: The gastric antrum extends from the incisura angularis to the pyloric opening.
Pylorus: The pylorus is the most distal segment of the stomach and consists of a thickened band of circular muscle that forms a sphincter functioning to control the rate of gastric emptying into the duodenum. The length of the pyloric canal is about 1cm in adults. It is characterized histologically by pyloric glands and the lack of parietal cells.
Other Features: Rugae are mucosal folds seen in the nondistended stomach. The areae gastricae represent the normal reticular mucosal pattern of the stomach, most prominent in the body and antrum. The lesser curvature forms the right gastric border and extends from the cardia to the pylorus. The greater curvature forms the left gastric border and extends from the cardia, over the dome of the fundus, to the pylorus.
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