What are the secretions of parietal and chief cells?
The two main types of exocrine secretory cells of the stomach are parietal cells and chief cells. Parietal cells secrete hydrochloric acid and chief cells secrete digestive enzymes such as pepsin.
Parietal cells (also known as oxyntic or delomorphous cells), are the epithelial cells that secrete hydrochloric acid (HCl) and intrinsic factor. These cells are located in the gastric glands found in the lining of the fundus and in the cardia of the stomach.
- Parietal cells produce gastric acid (hydrochloric acid) in response to histamine (via H2 receptors), acetylcholine (M3 receptors) and gastrin (gastrin receptors). Parietal cells contain an extensive secretory network (called canaliculi) from which the HCl is secreted by active transport into the stomach.
- The secretions of the exocrine gastric glands - composed of the mucous, parietal, and chief cells - make up the gastric juice. The products of the endocrine cells are secreted directly into the bloodstream and are not a part of the gastric juice.
- Pepsin is an endopeptidase that breaks down proteins into smaller peptides (that is, a protease). It is produced in the stomach and is one of the main digestive enzymes in the digestive systems of humans and many other animals, where it helps digest the proteins in food.
Chief cells (B or arrow) are located, in cluster, at the base of the glands. They synthesize and secret hydrolytic enzymes, which are activated at acid pH. These enzymes include gastric lipase, rennin and pepsin, which is secreted as pepsinogen and activated in the lumen. Pepsin hydrolyzes proteins.
- Alpha cells (A cells) secrete the hormone glucagon. Beta cells (B cells) produce insulin and are the most abundant of the islet cells. Delta cells (D cells) secrete the hormone somatostatin, which is also produced by a number of other endocrine cells in the body.
- Parathyroid chief cells (also called parathyroid principal cells or simply parathyroid cells) are one of the two cell types of the parathyroid glands, along with oxyphil cells. The chief cells are much more prevalent in the parathyroid gland than the oxyphil cells.
- Small pores called gastric pits contain many exocrine cells that secrete digestive enzymes and hydrochloric acid into the lumen, or hollow region, of the stomach. Mucous cells found throughout the stomach lining and gastric pits secrete mucus to protect the stomach from its own digestive secretions.
In anatomy, the G cell (or γ-cell) is a type of cell in the stomach and duodenum that secretes gastrin. It works in conjunction with gastric chief cells and parietal cells. G cells are found deep within the pyloric glands of the stomach antrum, and occasionally in the pancreas and duodenum.
- Delta cells (δ-cells or D cells) are somatostatin-producing cells. They can be found in the stomach, intestine and the pancreatic islets. Ghrelin can also strongly stimulate somatostatin secretion, thus indirectly inhibiting insulin release.
- THE STOMACH does not digest itself because it is lined with epithial cells, which produce mucus. This forms a barrier between the lining of the stomach and the contents. Enzymes, which make up part of the digestive juices are also secreted by the stomach wall, from glands with no mucus barrier.
- Intrinsic factor is a glycoprotein secreted by parietal (humans) or chief (rodents) cells of the gastric mucosa. In humans, it has an important role in the absorption of vitamin B12 (cobalamin) in the intestine, and failure to produce or utilize intrinsic factor results in the condition pernicious anemia.
Updated: 3rd October 2019