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In algae, akinetes form when environmental signals indicate impending change unfavorable to growth, such as the arrival of winter. Like cyanobacterial akinetes, they accumulate storage materials, but also develop thick cell walls and suspend active metabolism. [10] When conditions improve, the akinete germinates via the cell wall breaking open ...
Parietal cells produce potent hydrochloric acid, which damages cells. Gastric chief cells produce pepsinogen, which is activated by the acid to form pepsin. Pepsin is a protease that can digest and damage stomach cells. To prevent these disastrous effects, mucus and bicarbonate ions (HCO 3 −) are secreted by the foveolar cells.
These cells almost fill the tube and the remaining lumen is continued as a very fine channel. Cells found in the gastric glands include mucous neck cells, chief cells, parietal cells, G cells, and enterochromaffin-like cells (ECLs). The first cells of all of the glands are mucus-secreting foveolar cells that line the gastric pits.
A G cell or gastrin cell is a type of cell in the stomach and duodenum that secretes gastrin. It works in conjunction with gastric chief cells and parietal cells. G cells are found deep within the pyloric glands of the stomach antrum, and occasionally in the pancreas [1] and duodenum. The vagus nerve innervates the G cells.
The duct is lined by columnar cells, continuous with the epithelium lining the surface of the mucous membrane of the stomach, the tubes by shorter and more cubical cell which are finely granular. The glands contain mucous cells and G cells that secrete gastrin. [8] The pylorus also contains scattered parietal cells and neuroendocrine cells.
Whilst the muscularis externa is similar throughout the entire gastrointestinal tract, an exception is the stomach which has an additional inner oblique muscular layer to aid with grinding and mixing of food. The muscularis externa of the stomach is composed of the inner oblique layer, middle circular layer, and the outer longitudinal layer.
Goblet cells secrete mucus, which lubricates the passage of food along and protects the intestinal wall from digestive enzymes. In the small intestine, villi are folds of the mucosa that increase the surface area of the intestine.
Chief cells are part of fundic gland polyps (here shown in high magnification). [11]In gastric tissue, a loss of parietal cells due to chronic inflammation has been shown to affect chief cell differentiation and can induce chief cells to transdifferentiate back into neck cells and can lead to the formation of mucus cell metaplasia known as spasmolytic polypeptide expressing metaplasia (SPEM ...