Mills Ch22 Stomach

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SECTION VII : AlimentaryTract

Fundus

Cardiac area

Lesser curvature

Incisura

Corpus

Pylorus

Greater curvature

Antrum

FIGURE 22.1  Gross anatomical zones of the stomach.

FIGURE 22.3  Low-power viewof the gastric oxynticmucosa. The grooves in the mucosa are fixed anatomical features called areae gastricae.

mucosal diseases but causes confusion when describing gross anatomy. The junction between the antrum and the corpus is poorly demarcated. By external examination, it comprises the portion of the stomach distal to the incisura, a notch on the lesser curvature (1). Internally, the gastric mucosa is usually thrown into coarse folds called rugae. These are prominent when the stomach is empty but flattened out when the organ is distended. The rugae are most prominent in the corpus and fundus because this is where the major dilatation to accom- modate food occurs. The antrum is characterized by mucosa that is flatter and more firmly anchored to the underlying submucosa (Fig. 22.2).

The wall of the stomach has four layers: mucosa, sub- mucosa, muscularis propria, and subserosa. Apart from the mucosa, these layers are structurally similar to the bowel wall elsewhere in the gastrointestinal tract. When viewed close up, the surface of the mucosa is dissected by thin shal- low grooves termed areae gastricae (3). These are structurally fixed and do not flatten out when the stomach is distended. They are best seen when the mucosa is viewed en face with a hand lens. Areae gastricae may be demonstrated radiologi- cally via double-contrast barium examination but also can be recognized on histologic sections, particularly from gastrec- tomy specimens, where they appear as shallow depressions on an otherwise monotonously smooth surface (Fig. 22.3). Blood Supply Five arteries supply blood to the stomach. The left gastric artery arises directly from the celiac axis and supplies the cardiac region. The right gastric artery (which supplies the lesser curve) and the right gastroepiploic artery (which sup- plies the greater curve) arise from the hepatic artery. The left gastroepiploic and the short gastric arteries arise from the splenic artery and also supply the greater curvature. All these vessels anastomose freely, both on the subserosal layer of the stomach and in the muscularis propria, with extensive true plexus formation present within the submu- cosa. This richness of blood supply explains why it is so unusual to see gastric infarcts. The mucosal arteries are derived from this submucosal plexus but are end arteries that supply an area of mucosa that is largely independent of the adjacent mucosal arteries (4). Nerve Supply The sympathetic nerve supply to the stomach is derived from the celiac plexus via nerves that follow the gastric and gastroepiploic arteries. Branches also are received from the left and right phrenic nerves. The parasympathetic supply is the vagus nerve via the main anterior and posterior trunks

FIGURE 22.2  Mucosal zones of the stomach. The cardiac mucosa ( C ) is present distal to the lower end of the esophagus ( E ). The pyloric mucosa ( P ) occupies a triangular zone proximal to the duodenum ( D ). Elsewhere, the oxyntic mucosa ( F ) shows prominent rugal folds.