Stomach and Duodenum: Imaging Approach and Differential Diagnosis

Gastric Anatomy and Terminology

The stomach is the alimentary reservoir for the mixing, grinding, and enzymatic digestion of food. It is divided into the cardia, fundus, body, antrum, and pylorus; each with its own specific function.

The cardia is the portion of the stomach surrounding the esophageal orifice and the site where the lesser and greater curvatures meet. The fundus is the most cephalic part of the stomach and touches the left hemidiaphragm. The body is the main portion of the stomach and the principal site of acid production. The antrum is the prepyloric part of the stomach. The pylorus is the sphincter that controls emptying into the duodenum; it is formed by thickening of the middle layer of smooth muscle and a thin fibrous septum.

Mural Anatomy

The gastric wall consists of 3 layers of smooth muscle; the outermost is the longitudinal muscle layer, the middle is the circular muscle layer, and the inner is the oblique muscle layer. The middle circular muscle layer is the thickest component.

Gastric rugae are the redundant folds of gastric mucosa that are most prominent when the stomach is collapsed. The reservoir and mixing functions of the stomach demand a thick, expansile, muscular vessel, which characterizes gastric morphology.

Gastric mucosa is composed of columnar epithelium. Gastric glands vary in prevalence in different parts of the stomach. These produce mucin (to line and protect the gastric mucosa), pepsinogen (a precursor to pepsin needed for digestion), and hydrochloric acid (which activates digestive enzymes and assists with the breakdown of food).