G-cells are the cells that produce gastrin.
Gastrin is a peptide hormone primarily responsible for stimulating the secretion of hydrochloric acid (HCl) by the parietal cells in the stomach. It also stimulates gastric motility. G-cells are neuroendocrine cells, meaning they receive nervous signals and release hormones into the bloodstream.
Location of G-Cells:
- Pyloric Antrum: The majority of G-cells reside in the pyloric antrum of the stomach.
- Duodenum: A smaller number of G-cells can be found in the duodenum (the first part of the small intestine).
- Pancreas: Gastrin-producing cells have also been identified in the pancreas, although their role here is less well-understood.
Regulation of Gastrin Secretion:
G-cells release gastrin in response to several stimuli:
- Vagal Stimulation: Direct stimulation by vagal efferent neurons.
- Gastrin-Releasing Peptide (GRP): Stimulation by GRP neurons.
- Presence of peptides and amino acids in the stomach: Particularly phenylalanine and tryptophan.
- Stomach distension: Physical stretching of the stomach.
- Decreased gastric acidity: Reduced levels of acid in the stomach.
Gastrin secretion is inhibited by:
- Somatostatin: Released by D-cells.
- Increased gastric acidity: High levels of acid in the stomach (negative feedback).
- Secretin: Released by S-cells in the duodenum in response to acidic chyme.
In summary, G-cells, primarily located in the pyloric antrum of the stomach, are responsible for producing and secreting gastrin, a crucial hormone in gastric acid secretion and digestion.
