<P> The highest concentration that gastric acid reaches in the stomach is 160 mM in the canaliculi . This is about 3 million times that of arterial blood, but almost exactly isotonic with other bodily fluids . The lowest pH of the secreted acid is 0.8, but the acid is diluted in the stomach lumen to a pH between 1 and 3 . </P> <P> There is a small continuous basal secretion of gastric acid between meals of usually less than 10 mEq / hour . </P> <P> There are three phases in the secretion of gastric acid which increase the secretion rate in order to digest a meal: </P> <Ol> <Li> The cephalic phase: Thirty percent of the total gastric acid secretions to be produced is stimulated by anticipation of eating and the smell or taste of food . This signalling occurs from higher centres in the brain through the vagus nerve (Cranial Nerve X). It activates parietal cells to release acid and ECL cells to release histamine . The vagus nerve (CN X) also releases gastrin releasing peptide onto G cells . Finally, it also inhibits somatostatin release from D cells . </Li> <Li> The gastric phase: About sixty percent of the total acid for a meal is secreted in this phase . Acid secretion is stimulated by distension of the stomach and by amino acids present in the food . </Li> <Li> The intestinal phase: The remaining 10% of acid is secreted when chyme enters the small intestine, and is stimulated by small intestine distension and by amino acids . The duodenal cells release entero - oxyntin which acts on parietal cells without affecting gastrin . </Li> </Ol>

Amount of hydrochloric acid secreted daily by gastric glands is