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Parietal cells (also known as oxyntic cells) are epithelial cells in the stomach that secrete hydrochloric acid (HCl) and intrinsic factor. These cells are located in the gastric glands found in the lining of the fundus and body regions of the stomach. [ 1 ]
Gastric acid or stomach acid is the acidic component – hydrochloric acid of gastric juice, produced by parietal cells in the gastric glands of the stomach lining. In humans, the pH is between one and three, much lower than most other animals, but is very similar to that of carrion eating carnivores , needing protection from ingesting pathogens .
This is the major stimulus for acid secretion by parietal cells. [10] Along with the above-mentioned function, gastrin has been shown to have additional functions as well: Stimulates parietal cell maturation and fundal growth. Causes chief cells to secrete pepsinogen, the zymogen (inactive) form of the digestive enzyme pepsin.
A fourth phase of acid secretion is known as the basal state which occurs in the times between meals (interdigestive phase). The level of acid secretion during these times is regulated by body weight, individual, number of parietal cells, and time of day. Acid secretion is lowest in the morning before awakening and highest at night. [2]
The parietal cells secrete hydrochloric acid (gastric acid). This needs to be readily available for the stomach in a plentiful supply, and so from their positions in the walls, their secretory networks of fine channels called canaliculi can project and ingress into all the regions of the gastric-pit lumen.
The hydrogen potassium ATPase is activated indirectly by gastrin that causes ECL cells to release histamine. [11] The histamine binds to H2 receptors on the parietal cell, activating a cAMP-dependent pathway which causes the enzyme to move from the cytoplasmic tubular membranes to deeply folded canaliculi of the stimulated parietal cell. [2]
Enterochromaffin-like cells or ECL cells are a type of neuroendocrine cell found in the gastric glands of the gastric mucosa beneath the epithelium, in particular in the vicinity of parietal cells, that aid in the production of gastric acid via the release of histamine. They are also considered a type of enteroendocrine cell. [1]
Several types of endocrine cells are found in the gastric glands. The pyloric glands contain gastrin-producing cells ; this hormone stimulates acid production from the parietal cells. Enterochromaffin-like cells (ECLs), found in the oxyntic glands release histamine, which also is a powerful stimulant of the acid secretion.