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The parietal cell membrane is dynamic; the numbers of canaliculi rise and fall according to secretory need. This is accomplished by the fusion of canalicular precursors, or tubulovesicles , with the membrane to increase surface area, and the reciprocal endocytosis of the canaliculi (reforming the tubulovesicles) to decrease it.
Pepsin is expressed as a zymogen called pepsinogen, whose primary structure has an additional 44 amino acids compared to the active enzyme. In the stomach, gastric chief cells release pepsinogen. This zymogen is activated by hydrochloric acid (HCl), which is released from parietal cells in the stomach lining.
Cell proliferation and differentiation Growth hormone-releasing factor: Small intestine: Unclear Leptin: Stomach: Appetite control Motilin: Throughout the gut: Increases gastric emptying and small bowel motility Neuropeptide Y: Enteric nerves: Regulation of intestinal blood flow Neurotensin: Ileum: Affects gut motility; increases jejunal and ...
The parietal cell releases bicarbonate into the bloodstream in the process, which causes a temporary rise of pH in the blood, known as an alkaline tide. The gastric juice also contains digestive enzymes produced by other cells in the gastric glands – gastric chief cells. Gastric chief cells secrete an inactivated pepsinogen.
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:
Gastric chief cell Parietal cell. Chief cells (zymogen cells/peptic cells) – They are found in the basal regions of the gland and release proenzymes or zymogens – pepsinogen (precursor to pepsin), and prorennin (precursor to rennin or chymosin). [10] Prorennin is secreted in young mammals (childhood stage). It is not secreted in adult mammals.
Gastrointestinal physiology is the branch of human physiology that addresses the physical function of the gastrointestinal (GI) tract.The function of the GI tract is to process ingested food by mechanical and chemical means, extract nutrients and excrete waste products.
Gastric juice contains hydrochloric acid, pepsinogen and mucus. Hydrochloric acid is secreted by parietal cells, pepsinogen is secreted by gastric chief cells and mucus is secreted by mucous neck cells. [3]