Gross anatomists subdivide the stomach into four regions. The cardia surrounds the esophageal orifice; the fundus lies above the level of a horizontal line drawn through the esophageal (cardiac) orifice; the body lies below this line; and the pyloric part is the funnel-shaped region that leads into the pylorus, the distal, narrow sphincteric region between the stomach and duodenum. Histologists also subdivide the stomach, but into only three regions (Fig. 17.5). These subdivisions are based not on location but on the types of glands that occur in the gastric mucosa. The histologic regions are as follows:  Cardiac region (cardia), the part near the esophageal ori fice, which contains the cardiac glands (Fig. 17.6 and Plate 55, page 608) Pyloric region (pylorus), the part proximal to the pyloric sphincter, which contains the pyloric glands  Fundic region (fundus), the largest part of the stomach, which is situated between the cardia and pylorus and con tains the fundic or gastric glands (see Fig. 17.6)
Longitudinal submucosal folds, rugae, allow the stomach to distend when filled.
The stomach has the same general structural plan throughout, consisting of a mucosa, submucosa, muscularis externa, and serosa. Examination of the inner surface of the empty stomach reveals a number of longitudinal folds or ridges called rugae. They are prominent in the narrower regions of the stomach but poorly developed in the upper portion (see Fig. 17.5). When the stomach is fully distended, the rugae, composed of the mucosa and underlying submucosa, virtually disappear. The rugae do not alter total surface area; rather, they serve to accommodate expansion and filling of the stomach.
A view of the stomach’s surface with a hand lens shows that smaller regions of the mucosa are formed by grooves or
FIGURE 17.5 • Photograph of a hemisected human stomach.
This photograph shows the mucosal surface of the posterior wall of the stomach. Numerous longitudinal gastric folds are evident. These folds or rugae allow the stomach to distend as it fills. The histologic divisions of the stomach differ from the anatomic division. The former is based on the types of glands found in the mucosa. Histologically, the portion of the stomach adjacent to the entrance of the esophagus is the cardiac region (cardia) in which cardiac glands are located. A dashed line approximates its boundary. A slightly larger region leading toward the pyloric sphincter, the pyloric region (pylorus), contains the pyloric glands. Another dashed line approximates its boundary. The remainder of the stomach, the fundic region (fundus), is located between the two dashed lines and contains the fundic (gastric) glands.
shallow trenches that divide the stomach surface into bulging irregular areas called mamillated areas. These grooves provide a slightly increased surface area for secretion.
At higher magnification, numerous openings can be observed in the mucosal surface. These are the gastric pits, or foveolae. They can be readily demonstrated with the scanning electron microscope (Fig. 17.7). The gastric glands open into the bottom of the gastric pits.
Surface mucous cells line the inner surface of the stomach and the gastric pits.
The epithelium that lines the surface and the gastric pits of the stomach is simple columnar. The columnar cells are designated surface mucous cells. Each cell possesses a large, apical cup of mucinogen granules, creating a glandular sheet of cells (Fig. 17.8). The mucous cup occupies