Where is hcl produced in the stomach

Heliobacter pylori is a bacterium that thrives in the highly acidic environment of the stomach. Answer originally published November 13, Sign up for our email newsletter. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue.

See Subscription Options. For a long time the parietal cells of the gastric tubules were charged with the secretion of hydrochloric acid.

There is a degree of parallelism between the place of occurrence of a distinctly acid secretion, in the middle region of the stomach, and the distribution of the parietal cells. In the pyloric region, where the secretion is sometimes said to be alkaline, these histologic.

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Nerve endings in the stomach secrete two stimulatory neurotransmitters: acetylcholine and gastrin-releasing peptide. Their action is both direct on parietal cells and mediated through the secretion of gastrin from G cells and histamine from enterochromaffine-like cells. Gastrin acts on parietal cells directly and indirectly too, by stimulating the release of histamine.

The release of histamine is the most important positive regulation mechanism of the secretion of gastric acid in the stomach. Its release is stimulated by gastrin and acetylcholine and inhibited by somatostatin. In the duodenum, gastric acid is neutralised by sodium bicarbonate. This also blocks gastric enzymes that have their optima in the acid range of pH. The secretion of sodium bicarbonate from the pancreas is stimulated by secretin.

This polypeptide hormone becomes activated and secreted from so-called S cells in the mucosa of the duodenum and jejunum when the pH in duodenum falls below 4. The neutralisation is described by the equation:.

The carbonic acid instantly decomposes into carbon dioxide and water, then gets eliminated through urine. In hypochlorhydria and achlorhydria, there is low or no gastric acid in the stomach, potentially leading to problems as the disinfectant properties of the gastric lumen are decreased.

In such conditions, there is greater risk of infections of the digestive tract such as infection with Helicobacter or Vibrio bacteria Vibrio is a genus of Gram-negative bacteria possessing a curved rod shape, several species of which can cause food borne infection, usually associated with eating undercooked seafood. Typically found in saltwater, Vibrio are facultative anaerobes that test positive for oxidase and do not form spores. In Zollinger-Ellison syndrome and hypercalcaemia, there are increased gastrin levels, leading to excess gastric acid production, which can cause gastric ulcers.

The role of gastric acid in digestion was established in the s and s by William Beaumont on Alexis St. Martin, who, as a result of an accident, had a fistula hole in his stomach, which allowed Beaumont to observe the process of digestion and to extract gastric acid, verifying that acid played a crucial role in digestion. Martin, was accidentally shot in the stomach by a discharge of a musket loaded with a duck shot from close range that injured his ribs and his stomach.

Beaumont treated his wound, but expected St. Martin to die from his injuries. Despite this dire prediction, St. Martin survived — but with a hole, or fistula, in his stomach that never fully healed. Unable to continue work for the American Fur Company, he was hired as a handyman by Dr. Martin had come with him.

Beaumont recognised that he had in St. Martin the unique opportunity to observe digestive processes. Beaumont began to perform experiments on digestion using the stomach of St. Most of the experiments were conducted by tying a piece of food to a string and inserting it through the hole into St.

Every few hours, Beaumont would remove the food and observe how well it had been digested. Beaumont also extracted a sample of gastric acid from St. In September, Alexis St. Martin left Dr. Beaumont and moved to Canada, leaving Beaumont to concentrate on his duties as an army surgeon. Beaumont also used samples of stomach acid taken out of St. This led to the important discovery that the stomach acid, and not solely the mashing, pounding and squeezing of the stomach, digests the food into nutrients the stomach can use; in other words, digestion was primarily a chemical process and not a mechanical one.

During and , Dr. In he was transferred to St. Louis, Missouri. While en route to St. Louis, Alexis St. In early , Dr. Beaumont conducted another set of experiments on St. Beaumont left the army in and moved to Washington, D. There he met St. Martin once again, and performed another set of experiments on how various foods were digested in the stomach. In , Beaumont returned to Plattsburgh where he wrote a book about his experiments on digestion titled Experiments and Observations on the Gastric Juice and the Physiology of Digestion.

Martin returned to Canada during the spring of , and would never see Dr. Beaumont again, although he corresponded with the Beaumont family; St. Martin died in In , Beaumont re-enlisted and was stationed at St.

He left the service in , and maintained a private practice in St. Louis until his death in Beaumont is buried in Bellefontaine Cemetery St. Patients with symptomatic functional dyspepsia a disorder of digestive function characterised by discomfort or heartburn or nausea are more likely than people free of this condition to exhibit increased somatisation conversion of an emotional, mental, or psychosocial problem to a physical complaint , more stressful life events, less belief in religion, and drink less tea, suggests the article out in the European Journal of Gastroenterology and Hepatology.

The lead researchers say that this pattern of findings support a less reductionist approach and favours the strategy that includes considering the patient from a holistic view point. The findings of the study suggest the importance of adopting a more comprehensive holistic bio-psycho-socio-spiritual model when dealing with functional dyspepsia patients.

The researchers identified factors associated with dyspeptic symptoms by comparing demographic and psychosocial features in individuals exhibiting reddish streaks in the stomach, of whom 93 were symptomatic for functional dyspepsia and 67 asymptomatic. The two groups did not differ with regard to smoking behaviour, alcohol consumption, and coffee intake, but symptomatic patients were significantly less likely to drink tea than their asymptomatic peers, at Histamine from enterochromaffin-like cells may well be the primary modulator, but the magnitude of the stimulus appears to result from a complex additive or multiplicative interaction of signals of each type.

For example, the low amounts of histamine released constantly from mast cells in the gastric mucosa only weakly stimulate acid secretion, and similarly for low levels of gastrin or acetylcholine. However, when low levels of each are present, acid secretion is strongly forced. Additionally, pharmacologic antagonists of each of these molecules can block acid secretion.

Histamine's effect on the parietal cell is to activate adenylate cyclase , leading to elevation of intracellular cyclic AMP concentrations and activation of protein kinase A PKA. Binding of acetylcholine and gastrin both result in elevation of intracellular calcium concentrations. Several additional mediators have been shown to result in gastric acid secretion when infused into animals and people, including calcium, enkephalin and bombesin.

Calcium and bombesin both simulate gastrin release, while opiate receptors have been identified on parietal cells.