Gastric glands

The oxyntic gland and the pyloric gland are two types of glands in the stomach. The oxyntic gland, which is found in 80% of the stomach and is sometimes referred to simply as the gastric gland, is the most common form of gastric gland. The parietal cells that create hydrochloric acid and intrinsic factors are found in the oxyntic gland, which is an exocrine gland. Vitamin B12 absorption is dependent on intrinsic factors.

The pyloric gland, which is located in the pyloric region and occupies the remaining 20% of the stomach, is the other type of gland in the stomach. Gastrin is secreted by the G cells of the pyloric gland. Pyloric glands resemble oxyntic glands in form, however they are endocrine glands with few parietal cells.

Types of gland

Gastric glands are primarily exocrine glands that are found under the gastric pits within the gastric mucosa, which is the stomach’s mucous membrane. The mucosa of the stomach is pitted with numerous gastric pits, each containing 3-5 gastric glands. Foveolar (mucus), main cells, and parietal cells are exocrine gland cells. The pyloric gland, which is an endocrine gland that secretes the hormone gastrin generated by its G cells, is the other type of gastric gland.

The cardiac glands are found in the stomach’s cardia, which is the region closest to the heart and encloses the entrance where the oesophagus meets the stomach. Only cardiac glands are found here, and their primary function is mucus secretion. They are smaller and more shallowly positioned in the mucosa than the other gastric glands. Simple tubular with short ducts or compound racemose resembling the duodenal Brunner’s glands are the two types.

The fundic glands (also known as oxyntic glands) are located in the stomach’s fundus and body. They’re basic, practically straight tubes that connect to form a single duct when two or more are joined together. They release hydrochloric acid (HCl) and intrinsic factors, making them oxyntic.

The antrum of the pylorus houses the pyloric glands. Their G cells create gastrin, which they secrete.

Types of cell

The stomach mucosa contains millions of gastric pits, the narrowness of which defines the tubular shape of the gastric gland. More than one tube allows for multiple cell types to be accommodated. Each stomach gland has a similar shape, with a neck region closest to the pit entrance and basal regions on the lower portions of the tubes.] The epithelium from the gastric mucosa penetrates into the pit, where it transforms into short columnar granular cells near the neck. The remaining lumen is used as a very fine channel, and the cells almost completely fill the tube.

Foveolar cells, chief cells, parietal cells, G cells, enterochromaffin-like cells (ECLs), and other cells can be found in the stomach glands. Foveolar cells in the neck region, also known as mucous neck cells, are the earliest cells of all glands and create mucus. The mucus produced by the gastrointestinal mucosa is regarded to be distinct.

Another two cell types present in fundic glands in the fundus and throughout the body are gastric chief cells and parietal cells (oxyntic cells).

• Surface mucous cell (foveolar cell) – These mucous-producing cells line the lining of the stomach, shielding it from gastric acid’s corrosive effects. These cells line the mucosa of the stomach.
• Mucous neck cell – Mucous neck cells are distributed between parietal cells in gastric glands. These are shorter than their surface counterparts, and their apical surface contains less mucin granules.
• Chief cells (Zymogen cells/peptic cells) are present in the gland’s basal regions and produce proenzymes or zymogens such as pepsinogen (a precursor to pepsin) and prorennin (precursor to rennin or chymosin).
• In young mammals, pro renin is secreted (childhood stage). Adult mammals do not produce it. Adult mammals do not produce it. Gastric lipase is also produced in modest levels by chief cells. Gastric lipase plays a minor role in fat digestion.
• Parietal cells, also known as oxyntic cells, are most abundant on the side walls of the gastric glands (“parietal” meaning “related to a wall”). Hydrochloric acid, the major component of stomach acid, is secreted by the parietal cells. This must be readily available in a copious supply for the stomach, so that their secretory networks of fine channels called canaliculi can project and ingress into all regions of the gastric-pit lumen from their places in the walls. Castle’s intrinsic factor is another significant secretion of the parietal cells. Intrinsic factor is a glycoprotein that is required for vitamin B12 absorption. In reaction to histamine release from neighbouring ECLs, parietal cells make and release bicarbonate ions, and so play an important part in the pH buffering system.
• Enteroendocrine cells, also known as argentaffin cells, are found in the basal regions of the stomach glands and are divided into three types: D-cells, Enterochromaffin like cells (ECL-cells), and G-cells.
  • Serotonin and histamine are released by enterochromaffin like cells (ECL cells). When the pH of the stomach becomes too high, these cells accumulate and release histamine. The secretion of gastrin by the G cells stimulates the release of histamine. Histamine encourages the formation of HCL in the parietal cells and the release of protons into the stomach lumen. The ECLs stop producing histamine when the stomach pH drops (becomes more acidic).
  • Gastrin hormone is secreted by G cells. Gastrin induces the secretion of gastric juice by stimulating the gastric glands. These cells are usually located in the antrum of the pylorus’s pyloric glands, although some are also found in the duodenum and other organs. These glands’ gastric pits are much deeper than the others’, and gastrin is released into the circulation rather than the lumen.
  • Somatostatin is secreted by D cells. The hormone somatostatin inhibits the release of hormones from the gastrointestinal tract.

Clinical significance

Fundic gland polyposis is a medical condition in which the fundus and stomach body produce many fundic gland polyps.

Damaged parietal cells fail to create the intrinsic factor required for vitamin B12 absorption, resulting in pernicious anemia. Vitamin B12 insufficiency is most commonly caused by this.

Conclusion

The gastric glands are the tube-like, branched structures found on the stomach’s inner lining. These glands are the digestive system’s basic secretory unit, and they’re made up of a variety of cell components that each perform a unique role. The gastric pits, which are located on the stomach’s gastric mucosa, are the source of these glands.