Mills Ch22 Stomach

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SECTION VII : AlimentaryTract

positively with PAS/diastase and with Alcian blue at pH 2.5 (17). Mucous neck cells are found in lesser numbers in the isthmic portion of the glands, and occasional parietal cells can be encountered in the basal portion of the glands. Mucous neck cells are also present in the pyloric mucosa. Studies indicate that the mucous neck cells located in glands from all areas of the stomach have proliferation and mucosal regeneration as their major functions. These undif- ferentiated cells act as stem cells and may migrate upward to renew parietal cells, foveolar and surface epithelia or downward to renew zymogenic or neuroendocrine cells (18). It has been estimated that, in humans, the gastric sur- face epithelium is normally replaced every 4 to 8 days. The parietal and zymogenic cells turn over much more slowly, likely every 1 to 3 years. Endocrine Cells The stomach contains a wide variety of hormone-producing cells. In the pyloric mucosa, about 50% of the whole endo- crine cell population is G cells (gastrin producing), 30% are enterochromaffin (EC) cells (serotonin producing), and 15% are D cells (somatostatin producing). In the oxyntic mucosa, however, a major portion of the endocrine cells are entero- chromaffin like (ECL) and secrete histamine. Small num- bers of X cells (secretion product unknown) and EC cells are also present. In the oxyntic mucosa, the cells secreting these hormones are mostly located in the glands, particularly toward the base. They are inconspicuous and are difficult to detect without the use of special stains. Their numbers are variable but generally there are less than 20 cells per gland, with most glands containing less than 10 cells (Fig. 22.12A). In the pyloric mucosa, endocrine cells are most common in the neck region. On routine sections, they are rounded

FIGURE 22.11  Oxyntic mucosa. The surface and foveolar lining epithe- lia are intensely positive. Paler-staining mucous neck cells are present within the glands (PAS).

reticulum containing ribosomal ribonucleic acid (RNA). The isthmic (most superficial) portion of the glands contains predominantly parietal cells (acid and intrinsic factor secret- ing). These are roughly triangular, with their base along the basement membrane. The nuclei are centrally placed with evenly distributed chromatin, and the cytoplasm stains a deep pink (acidophilic) on well-differentiated H&E-stained sections (Fig. 22.10). This staining property of the parietal cell cytoplasm reflects the presence of abundant microca- naliculi that consist entirely of protein. The neck (middle) portion of the fundic glands contains a mixture of zymogenic and parietal cells, together with a third type, mucous neck cells (Fig. 22.11). Mucous neck cells are difficult to recog- nize on an H&E stain but are easily identified using a PAS stain, where they are seen to resemble the mucus-secreting cells of the cardiac and pyloric glands. These cells produce neutral and acidic mucin, especially sialomucin, which stains

A

B

FIGURE 22.12  A: Endocrine cells in gastric oxyntic glands. Only scanty numbers of cells are present. The brown staining of the surface mucus is an artifact (immunostain for synaptophysin). B: Endocrine cells in the gastric pyloric mucosa. The cells are numerous and located predominately in the mucous neck region (immunostain for synaptophysin).