Final answer:
Gastrin stimulates enteroendocrine G cells to secrete histamine, which in turn prompts parietal cells to produce HCl. This acid is crucial for the digestive process in the stomach, converting pepsinogen to pepsin for protein digestion.
Step-by-step explanation:
Gastrin stimulates enteroendocrine cells to secrete histamine, and histamine stimulates parietal cells to secrete HCl (hydrochloric acid).
These processes play a critical role in the digestive function of the stomach. Gastrin, which is released mainly by enteroendocrine G cells, prompts the parietal cells to increase production of HCl, essential for converting pepsinogen to pepsin and for protein digestion. The increased secretion of gastric juice facilitated by acetylcholine, gastrin, and histamine helps in creating an acidic environment that is necessary for proper digestion.
Chief cells, located in the gastric glands, are responsible for secreting pepsinogen. This inactive proenzyme is converted into active pepsin by the HCl produced by the parietal cells.
Moreover, the release of gastrin also triggers smooth muscle contractions, contributing to the stomach's mechanical digestion. The secretion of additional hormones like motilin and secretin further manages various aspects of gastrointestinal activity, including gastric emptying, intestinal peristalsis, and bicarbonate secretion.