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A canaliculus is an adaptation found on gastric parietal cells. It is a deep infolding, or little channel, which serves to increase the surface area, e.g. for secretion. The parietal cell membrane is dynamic; the numbers of canaliculi rise and fall according to secretory need.
These slow wave potentials must reach a threshold level for the action potential to occur, whereupon Ca 2+ channels on the smooth muscle open and an action potential occurs. As the contraction is graded based upon how much Ca 2+ enters the cell, the longer the duration of slow wave, the more action potentials occur.
50-60% of total gastric acid secretion occurs during this phase. The gastric phase is a period in which swallowed food and semidigested protein (peptides and amino acids) activate gastric activity. Ingested food stimulates gastric activity in two ways: by stretching the stomach and by gastric contents stimulating receptors in the stomach. [ 2 ]
The muscle of the inner layer is arranged in circular rings around the tract, whereas the muscle of the outer layer is arranged longitudinally. The stomach has an extra layer, an inner oblique muscular layer. [1] Between the two muscle layers is the myenteric plexus (Auerbach's plexus). This controls peristalsis.
Gastrin is a linear peptide hormone produced by G cells of the duodenum and in the pyloric antrum of the stomach.It is secreted into the bloodstream. The encoded polypeptide is preprogastrin, which is cleaved by enzymes in posttranslational modification to produce progastrin (an intermediate, inactive precursor) and then gastrin in various forms, primarily the following three:
The first cells of all of the glands are mucus-secreting foveolar cells that line the gastric pits. The mucus produced here is less acidic than that produced by the mucous neck cells. Fundic glands found in the fundus and also in the body have another two cell types–gastric chief cells and parietal cells (oxyntic cells).
During hydrochloric acid secretion in the stomach, the gastric parietal cells extract chloride anions, carbon dioxide, water and sodium cations from the blood plasma and in turn release bicarbonate back into the plasma after forming it from carbon dioxide and water constituents. This is to maintain the plasma's electrical balance, as the ...
Several types of endocrine cells are found in the gastric glands. The pyloric glands contain gastrin -producing cells ( G cells ); this hormone stimulates acid production from the parietal cells. Enterochromaffin-like cells (ECLs), found in the oxyntic glands release histamine , which also is a powerful stimulant of the acid secretion.