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The secretions of the different exocrine gastric gland cells produce a watery, acidic fluid into the stomach lumen called gastric juice. [5] [6] Gastric juice contains water, hydrochloric acid, intrinsic factor, pepsinogen, and salts. Adults produce around two to three litres of gastric juice per day. [5]
The pH of the secreted fluid can fall by 0.8. Gastrin primarily induces acid-secretion indirectly, increasing histamine synthesis in ECL cells, which in turn signal parietal cells via histamine release and H 2 stimulation. [6] Gastrin itself has no effect on the maximum histamine-stimulated gastric acid secretion. [7]
Parietal cells contain an extensive secretory network (called canaliculi) from which the hydrochloric acid is secreted into the lumen of the stomach. The pH of gastric acid is 1.5 to 3.5 in the human stomach lumen, a level maintained by the proton pump H + /K + ATPase . [ 1 ]
Chyme is part liquid and part solid: a thick semifluid mass of partially digested food and digestive secretions that is formed in the stomach and small intestine during digestion. Chyme also contains cells from the mouth and esophagus that slough off from the mechanical action of chewing and swallowing.
The coordinated contractions of these layers is called peristalsis and propels the food through the tract. Food in the GI tract is called a bolus (ball of food) from the mouth down to the stomach. After the stomach, the food is partially digested and semi-liquid, and is referred to as chyme. In the large intestine the remaining semi-solid ...
The parietal cells in the fundus of the stomach, produce a glycoprotein called intrinsic factor which is essential for the absorption of vitamin B12. Vitamin B12 (cobalamin), is carried to, and through the stomach, bound to a glycoprotein secreted by the salivary glands – transcobalamin I also called haptocorrin, which protects the acid ...
In fact, the stomach and thyroid share iodine-concentrating ability and many morphological and functional similarities, such as cell polarity and apical microvilli, similar organ-specific antigens and associated autoimmune diseases, secretion of glycoproteins (thyroglobulin and mucin) and peptide hormones, the digesting and readsorbing ability ...
Diagram showing bicarbonate secretion to the stomach lumen. The mucus produced by these cells is extremely important, as it prevents the stomach from digesting itself. [5] 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 ...