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Gastric activity involved in digestion is divided into three phases of digestion known as the cephalic phase, the gastric phase, and the intestinal phase. These phases overlap and all three can occur simultaneously. [1] A fourth phase of acid secretion is known as the basal state which occurs in the times between meals (interdigestive phase).
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 n
Determinants of gastric acid secretion. Gastric acid or stomach acid is the acidic component – hydrochloric acid of gastric juice, produced by parietal cells in the gastric glands of the stomach lining. In humans, the pH is between one and three, much lower than most other animals, but is very similar to that of carrion eating carnivores ...
As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach. Inhibition of gastrin and gastric acid secretion is lifted. This triggers G cells to release gastrin, which in turn stimulates parietal cells to secrete gastric acid. Gastric acid is about 0.5% hydrochloric acid, which lowers the pH to the desired pH ...
The stomach is a distensible organ and can normally expand to hold about one litre of food. [22] This expansion is enabled by a series of gastric folds in the inner walls of the stomach. The stomach of a newborn baby will only be able to expand to retain about 30 ml.
H + is pumped into the stomach by exchanging it with K +. This process also requires ATP as a source of energy; however, Cl − then follows the positive charge in the H + through an open apical channel protein. HCO 3 − secretion occurs to neutralize the acid secretions that make their way into the duodenum of the small intestine.
The gastric hydrogen potassium ATPase or H + /K + ATPase is the proton pump of the stomach.It exchanges potassium from the intestinal lumen with cytoplasmic hydronium [2] and is the enzyme primarily responsible for the acidification of the stomach contents and the activation of the digestive enzyme pepsin [3] (see gastric acid).
The enterogastric reflex is one of the three extrinsic reflexes of the gastrointestinal tract, the other two being the gastroileal reflex and the gastrocolic reflex. [1] The enterogastric reflex is stimulated by duodenal distension. [2] It can also be stimulated by a pH of 3-4 in the duodenum and by a pH of 1.5 in the