Gastric acid is, together with several enzymes and the intrinsic factor, one of the main secretions of the stomach. Chemically it is an acid solution consisting mainly of hydrochloric acid, but also containing small quantities of potassium chloride (KCl) and sodium chloride (NaCl). Intrinsic factor is a glycoprotein produced by the parietal cells of the stomach. ... Secretion is the process of segregating, elaborating, and releasing chemicals from a cell, or a secreted chemical substance or amount of substance. ... With the exception of the animal varients box, this article deals with the human stomach. ... The chemical compound hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride gas (HCl). ... The chemical compound potassium chloride (KCl) is a metal halide composed of potassium and chlorine. ... This articles section called Other facts does not adequately cite its references or sources. ...

Physiology

Diagram summarising control of stomach acid secretion, emphasising interaction between the body and antrum.

Gastric acid is produced by parietal cells (also known as oxyntic cells) in the stomach. Its secretion is a complex and energetically expensive process. Parietal cells contain an extensive secretory network (called canaliculi) from which the gastric acid is secreted into the lumen of the stomach. These cells are part of epithelial fundic glands in the gastric mucosa. The pH of gastric acid is 2-3 in the stomach lumen, the acidity being maintained by the proton pump, a H⁺/K⁺ ATPase. The parietal cell releases bicarbonate into the blood stream in the process, which causes the temporary rise of pH in the blood, known as alkaline tide. Download high resolution version (987x1194, 199 KB)Diagram summarising control of stomach acid secretion. ... Download high resolution version (987x1194, 199 KB)Diagram summarising control of stomach acid secretion. ... Parietal cells (also called oxyntic cells) are cells located in the stomach epithelium. ... This article does not adequately cite its references or sources. ... Types of epithelium This article discusses the epithelium, an animal anatomical structure. ... The fundus glands (or fundic glands) are found in the body and fundus of the stomach; they are simple tubes, two or more of which open into a single duct. ... The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. ... The correct title of this article is . ... Lumen can mean: Lumen (unit), the SI unit of luminous flux Lumen (anatomy), the cavity or channel within a tubular structure Thylakoid lumen, the inner membrane space of the chloroplast 141 Lumen, an asteroid discovered by the French astronomer Paul Henry in 1875 Lumen (band), an American post-rock band... A proton pump is an integral membrane protein that is capable of moving protons across the membrane of a cell, mitochondrion, or other subcellular compartment, thereby creating a difference or gradient in both pH and electrical charge (ignoring differences in buffer capacity) and tending to establish an electrochemical potential. ... Gastric hydrogen potassium ATPase also know as H+/K+ ATPase // Function and location The gastric hygrogen potassium ATPase or H+/K+ ATPase is the proton pump of the stomach and as such is the enzyme primarily responsible for the acidification of the stomach contents. ... In inorganic chemistry, a bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. ... There are very few or no other articles that link to this one. ...

The resulting highly acidic environment in the stomach lumen causes proteins from food to lose their characteristic folded structure (or denature). This exposes the protein's peptide bonds. The gastric acid also activates pepsinogen into pepsin - this enzyme then helps digestion by breaking the bonds linking amino acids, a process known as proteolysis. In addition, many bacteria cannot survive in such an acidic environment, preventing bacteria found in foods from infecting the body. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Irreversible egg protein denaturation and loss of solubility, caused by the high temperature (while cooking it) In biochemistry, denaturation is a structural change in biomolecules such as nucleic acids and proteins, such that they are no longer in their native state, and their shape which allows for optimal activity. ... A peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... Pepsin is a digestive protease (EC 3. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Phenylalanine is one of the standard amino acids. ... Proteolysis is the directed degradation (digestion) of proteins by cellular enzymes called proteases or by intramolecular digestion. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ...

Secretion

The gastric acid secretion happens in several steps. Chloride and hydrogen ions are secreted separately from the cytoplasm of parietal cells and get combined into HCl only in their canaliculi. Gastric acid is then secreted into the lumen of the oxyntic gland and gradually reaches the main stomach lumen.

The highest concentration that it 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 about 0.8, but the acid gets diluted in the stomach lumen to the pH between 2 and 3. Section of an artery For other uses, see Artery (disambiguation). ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... This article or section does not adequately cite its references or sources. ... Lumen can mean: Lumen (unit), the SI unit of luminous flux Lumen (anatomy), the cavity or channel within a tubular structure Thylakoid lumen, the inner membrane space of the chloroplast 141 Lumen, an asteroid discovered by the French astronomer Paul Henry in 1875 Lumen (band), an American post-rock band...

At first, negative chloride ions and sodium ions get secreted actively from the cytoplasm of the parietal cell into the lumen of the canaliculus. This creates a negative potential of -40 mV (millivolts)to -70 mV across the membrane that enables the diffusion of potassium ions and a small number of sodium ions from the cytoplasm into the canaliculus. Organelles. ... Transmembrane potential difference is the electrical potential difference across a plasma membrane. ... Josephson junction array chip developed by NIST as a standard volt. ... This article or section does not cite its references or sources. ... This article does not adequately cite its references or sources. ...

Another step is the production of hydrogen ions in the cytoplasm of parietal cells. The enzyme carbonic anhydrase catalyses the reaction between carbon dioxide and water, in which carbonic acid is produced. This acid immediately dissociates into hydrogen ions and hydrogen carbonate ions. The hydrogen ions leave the cell by the aid of H⁺/K⁺ ATPase antiporter. Carbonic anhydrase (carbonate dehydratase) is a family of metalloenzymes (enzymes that contain one or more metal atoms as a functional component of the enzyme) that catalyze the rapid interconversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions. ... Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3. ... Gastric hydrogen potassium ATPase also know as H+/K+ ATPase // Function and location The gastric hygrogen potassium ATPase or H+/K+ ATPase is the proton pump of the stomach and as such is the enzyme primarily responsible for the acidification of the stomach contents. ... An antiporter is an integral membrane protein that is involved in secondary active transport. ...

At the same time sodium ions are actively reabsorbed. This means the largest amount of secreted K⁺ and Na⁺ ions return into the cytoplasm. In the canaliculus, secreted hydrogen and chloride ions combine into HCl and are then secreted into the lumen of the oxyntic gland.

Regulation of secretion

Gastric acid production is regulated by both the autonomic nervous system and several hormones. The parasympathetic nervous system, via the vagus nerve, and the hormone gastrin stimulate the parietal cell to produce gastric acid, both directly acting on parietal cells and indirectly, through the stimulation of the secretion of the hormone histamine from enterochromaffine-like cells (ELC). Vasoactive intestinal peptide, cholecystokinin, and secretin all inhibit production. This article or section is in need of attention from an expert on the subject. ... Norepinephrine A hormone (from Greek όρμή - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... Autonomic nervous system innervation, showing the sympathetic and parasympathetic (craniosacral) systems, in red and blue, respectively The parasympathetic nervous system is one of three divisions of the autonomic nervous system. ... The vagus nerve (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired cranial nerves, and is the only nerve that starts in the brainstem (within the medulla oblongata) and extends, through the jugular foramen, down below the head, to the abdomen. ... In humans, gastrin is a hormone that stimulates secretion of gastric acid by the stomach. ... This article or section does not cite its references or sources. ... Enterochromaffin-like cells or ECL cells are a type of neuroendocrine cells found in the gastric mucosa beneath the epithelium, particularly in the vicinity of parietal cells. ... VIP is a peptide hormone containing 28 amino acid residues. ... Cholecystokinin (from Greek chole, bile; cysto, sac; kinin, move; hence, move the bile-sac (gall bladder)) is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein. ... Secretin is a peptide hormone produced in the S cells of the duodenum. ...

The production of gastric acid in the stomach is tightly regulated by positive regulators and negative feedback mechanisms. Four types of cells are involved in this process: parietal cells, G cells, D cells and enterochromaffine-like cells. Besides this, the endings of the vagus nerve (X) and the intramural nervous plecus in the digestive tract influence the secretion significantly. Negative feedback is a type of feedback in which the system responds in an opposite direction to the perturbation. ... In medicine, the G cell is a type of cell in the stomach that secrets gastrin. ... D cells are cells located in the stomach. ...

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. Chemical structure of D-Aspartic Acid, a common Amino Acid neurotransmitter. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Gastrin releasing peptide (GRP) is released by the post-ganglionic fibres of the vagus nerve which innervate the G cells of the stomach and stimulate them to release gastrin. ...

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. Somatostatin is a hormone. ...

Neutralization

In the duodenum, gastric acid is neutralized 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 gets activated and secreted from so-called S cells in the mucosa of the duodenum and jejunum when the pH in duodenum falls below 4.5 to 5.0. The neutralization is described by the equation: In anatomy of the digestive system, the duodenum is a hollow jointed tube connecting the stomach to the jejunum. ... Neutralization is a chemical reaction in which an acid and a base react and produce salt and water. ... Sodium bicarbonate is the chemical compound with the formula NaHCO3. ... The correct title of this article is . ... The pancreas is an organ in the digestive and endocrine system (of vertebrates[2]). It is both exocrine (secreting pancreatic juice containing digestive enzymes) and endocrine (producing several important hormones, including insulin, glucagon, and somatostatin). ... Secretin is a peptide hormone produced in the S cells of the duodenum. ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... S cells are cells which release secretin, found in the jejunum and duodenum. ... Diagram of the Human Intestine In anatomy of the digestive system, the jejunum is the central of the three divisions of the small intestine and lies between the duodenum and the ileum. ...

HCl + NaHCO₃ → NaCl + H₂CO₃

The carbonic acid instantly dissociates into carbon dioxide and water, then gets eliminated through urine. Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... This article describes water from a scientific and technical perspective. ... This article or section is in need of attention from an expert on the subject. ...

Safety mechanisms

There are several safety mechanisms that prevent the damage of gastric epithelium. Nonetheless, when due to different reasons these fail (e.g. because of excess acid production), this can lead to heartburn or peptic ulcers. A benign gastric ulcer (from the antrum) of a gastrectomy specimen. ...

Role in disease

In hypochlorhydria and achlorhydria, the parietal cells are unable to produce the required amount of gastric acid in the stomach, potentially leading to gastroenteritis. Also the disinfectant properties of the gastric milieu are decreased, leading to an increased risk of infections of the digestive tract (such as the foodborne infection with Vibrio vulnificus). Achlorhydria or hypochlorhydria is decreased production of gastric acid by the stomach. ... Achlorhydria or hypochlorhydria is decreased production of gastric acid by the stomach. ... Gastroenteritis involves diarrhea or vomiting, with noninflammatory infection of the upper small bowel, or inflammatory infection of the colon, both part of the gastrointestinal tract. ... Disinfection of a floor using a mop Disinfectants are antimicrobial agents that are applied to non-living objects to destroy microorganisms, the process of which is known as disinfection. ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... This article does not cite its references or sources. ...

In Zollinger-Ellison syndrome and hypercalcemia, there are increased gastrin levels, leading to excess gastric acid production, which can cause gastric ulcers. Zollinger-Ellison syndrome is a disorder where increased levels of the hormone gastrin are produced, causing the stomach to produce excess hydrochloric acid. ... Hypercalcaemia is an elevated calcium level in the blood. ... In humans, gastrin is a hormone that stimulates secretion of gastric acid by the stomach. ...

In diseases featuring excess vomiting, patients develop hypochloremic metabolic alkalosis (decreased blood acidity by H⁺ and chlorine depletion). General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Metabolic alkalosis results from altered metabolism. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Standard atomic weight 35. ...

Pharmacology

The proton pump enzyme is the target of proton pump inhibitors, used to increase gastric pH in diseases which feature excess acid. H2 antagonists indirectly decrease gastric acid production. Antacids neutralize existing acid. Proton pump inhibitors (or PPIs) are a group of drugs whose main action is pronounced and long-lasting reduction of gastric acid production. ... A bottle of antacid tablets An antacid is any substance, generally a base, which counteracts stomach acidity. ...

External links

See also

• Stomach
• Digestion