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The stomach receives food from the esophagus and has four functions: (1) it acts as a reservoir that permits eating reasonably large quantities of food at intervals of several hours; (2) food contained in the stomach is mixed, and delivered into the duodenum in amounts regulated by its chemical nature and texture; (3) the first stages of protein and carbohydrate digestion are carried out in the stomach; and (4) a few substances are absorbed across the gastric mucosa.
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The anatomy of the stomach in Figures 23–1, 23–2, and 23–3 illustrates the structure supporting the functions.
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The cardia is located at the gastroesophageal junction. The fundus is the portion of the stomach that lies cephalad to the gastroesophageal junction. The corpus is the capacious central part; division of the corpus from the pyloric antrum is marked approximately by the angular incisure, a crease on the lesser curvature just proximal to the “crow’s-foot” terminations of the nerves of Latarjet (Figure 23–3). The pylorus is the boundary between the stomach and the duodenum.
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The cardiac gland area is the small segment located at the gastroesophageal junction. Histologically, it contains principally mucus-secreting cells, though a few parietal cells are sometimes present. The oxyntic gland area is the portion containing parietal (oxyntic) cells and chief cells (Figure 23–2). The boundary between this region and the adjacent pyloric gland area is reasonably sharp, since the zone of transition spans a segment of only 1–1.5 cm. The pyloric gland area constitutes the distal 30% of the stomach and contains the G cells that manufacture gastrin. Mucous cells are common in the oxyntic and pyloric gland areas.
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As in the rest of the gastrointestinal tract, the muscular wall of the stomach is composed of an outer longitudinal and an inner circular layer. An additional incomplete ...