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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 secretion is a complex and relatively energetically expensive process. 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 or chymus (/ k aɪ m /; from Greek χυμός khymos, "juice" [1] [2]) is the semi-fluid mass of partly digested food that is expelled by the stomach, through the pyloric valve, into the duodenum [3] (the beginning of the small intestine).
Mucus is released in the stomach and intestine, and serves to lubricate and protect the inner mucosa of the tract. It is composed of a specific family of glycoproteins termed mucins and is generally very viscous. Mucus is made by two types of specialized cells termed mucous cells in the stomach and goblet cells in the intestines. Signals for ...
Secretion of the hormone intestinal gastrin: I cells: Intestinal glands of duodenum: Secretion of the hormone cholecystokinin, which stimulates release of pancreatic juices and bile K cells: Intestinal glands: Secretion of the hormone glucose-dependent insulinotropic peptide, which stimulates the release of insulin M cells
The chyme is very acidic, with a low pH, having been released from the stomach and needs to be made much more alkaline. This is achieved in the duodenum by the addition of bile from the gall bladder combined with the bicarbonate secretions from the pancreatic duct and also from secretions of bicarbonate-rich mucus from duodenal glands known as ...
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]
The stomach is involved in the gastric phase of digestion, following the cephalic phase in which the sight and smell of food and the act of chewing are stimuli. In the stomach a chemical breakdown of food takes place by means of secreted digestive enzymes and gastric acid. The stomach is located between the esophagus and the small intestine.