The majority of human cardiac glands that lie immediately distal to the termination of esophageal epithelium are compound or branched tubular glands. They empty into overlying gastric pits. The glands of this region are often organized into lobule-like complexes by the surrounding connective tissue of the lamina propria. The secretory tubules contain mucous cells, parietal cells and endocrine cells. The mucous cell is the most common cell type observed and appears to comprise two populations. The majority are pyramidal in shape and show numerous spherical, electron-dense secretory granules. Profiles of rough endoplasmic reticulum are observed scattered throughout the cytoplasm and Golgi complexes occupy a supranuclear position in relation to forming secretory granules. Morphologically this cell type appears similar to the mucous neck cell of the fundus. Secretory granules of a second mucous cell type are mottled in appearance and show an area of increased electron density near the limiting membrane. Parietal cells are observed and appear identical to those in the fundus. The large number of endocrine cells present raises questions concerning the traditional concept of the function of these particular glands.
Aspirin alters the gastric mucosal barrier as measured by ionic flux and potential difference. The effect of cimetidine on aspirin-induced alterations in gastric mucosa was studied in five normal male volunteers. Aspirin effects were studied with and without previous treatment with cimetidine. Mean (+/- SEM) basal potential difference was -48 +/- 1 mV. After 600 mg of aspirin in 1 dl of isotonic saline, potential difference decreased in 10 min to -39 +/- 1 mV (P less than 0.001) and returned to baseline within 60 min. Control biopsies showed 2% damaged mucosal cells compared with 20% damaged at the time of maximal drop in potential difference (P less than 0.001) after aspirin. Recovery to 9% damage occurred by 60 min. In subjects pretreated with 300 mg cimetidine, potential difference rose during 1 h to -62 +/- 1 mV (P less than 0.001). After aspirin potential difference fell to -48 +/- 1 mV compared with -39 +/- 1 mV with aspirin alone (P less than 0.01) and returned to -62 +/- 1 mV at 60 min. The cimetidine-treated group showed 4% mucosal damage at the peak potential difference fall after aspirin, significantly less (P less than 0.02) than in the untreated subjects.
The human pyloric glands are simple or branched tubular glands which spiral through the connective tissue of the lamina propria. They are comprised of three cell types: the pyloric gland (mucous) cell, the parietal cell, and endocrine cells. The mucous cell is the most common cell type in the human pyloric glands and is characterized by an abundance of secretory granules. The secretory granules are usually round in shape and vary considerably in diameter. They are membrane-bound and comprise a heterogeneous population. The larger granules contain a light staining amorphous material and often possess an area of increased electron density near the limiting membrane of the granule giving them a mottled appearance. A smaller, more electron-dense secretory granule also is found both in relation to the Golgi complex and cell apex.The morphological observations indicate that the mechanism of mucin production by the mucous cells of the human pyloric glands may be similar to that reported in other mucin-secreting cells.
Biopsies from the fundic mucosa of healthy volunteers were examined by scanning electron microscopy following blunt dissection and freeze fracture. The mucosal surface exhibited a cobblestone appearance. With increased magnification, microvilli could be demonstrated on the luminal surface of individual surface cells. Blunt dissection of the gastric mucosa revealed tubular gastric pits descending from the surface until they opened into branched tubular gastric glands. The gastric glands are irregular in outline due to the knoblike projections of individual parietal cells. The internal structure of the component cells also was examined with the scanning electron microscope following freeze fracture. Mucous granules were observed in the apical portion of surface epithelial cells. Lumina of parietal cell canaliculi were found to be continuous with the lumen of the gastric glands. Pepsinogen granules could be seen throughout the cytoplasm of chief cells. The blunt dissection-freeze fracture technique utilizing the scanning electron microscope allows, for the first time, a three-dimensional view of human gastric mucosa, including the gastric pits and glands as well as some of the internal architecture of component cells.
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