The stomach receives food from the esophagus and has four functions: (1) to act as a reservoir that permits eating boluses of food at intervals of several hours; (2) to mix and deliver food into the duodenum in amounts regulated by its chemical nature and texture; (3) to facilitate the first stages of protein and carbohydrate digestion; and (4) to absorb some small molecules across the gastric mucosa.
The anatomy of the stomach is illustrated in Figures 25–1, 25–2, and 25–3. Because of its size and varying functions, the stomach is divided into loosely defined areas. The cardia is the region of the stomach located at the gastroesophageal junction. The portion of the stomach that lies cephalad to the gastroesophageal junction is known as the fundus. The body is the capacious central part; division of the body 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 25–3). The pylorus is the boundary between the stomach and the duodenum.
Names of the parts of the stomach. The line drawn from the lesser to the greater curvature depicts the approximate boundary between the oxyntic gland area and the pyloric gland area. No prominent landmark exists to distinguish between antrum and body (corpus). The fundus is the portion craniad to the esophagogastric junction. The cardiac gland area is adjacent to the gastroesophageal junction, again without a clear anatomic boundary.
Histologic features of the mucosa in the oxyntic gland area. Each gastric pit drains three to seven tubular gastric glands. A: The neck of the gland contains many mucous cells. Oxyntic (parietal) cells are most numerous in the mid-portion of the glands; peptic (chief) cells predominate in the basal portion. B: Drawing from photomicrograph of the gastric mucosa.
Blood supply and parasympathetic innervation of the stomach and duodenum.
Different areas of the stomach contain different histologic cell types. The cardiac gland area is the small segment located at the gastroesophageal junction. It primarily contains mucus-secreting cells, although a few parietal cells are sometimes present. The oxyntic gland area is the portion containing parietal (oxyntic) cells and chief cells (Figure 25–2). 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.