HC1 secretion in gastric phase is increase by
**Core Concept**
The gastric phase of gastric acid secretion is primarily controlled by the release of gastrin, a peptide hormone secreted by G cells in the antrum of the stomach. The increase in gastrin levels stimulates the parietal cells in the gastric glands to secrete more hydrochloric acid (HCl).
**Why the Correct Answer is Right**
During the gastric phase, the antrum of the stomach is distended by the presence of food, which stimulates the release of gastrin. Gastrin then binds to its receptors on the parietal cells, leading to an increase in the production of HCl. This process is mediated by the activation of the G-protein coupled receptor, which increases the activity of the enzyme H+/K+ ATPase, also known as the proton pump, on the surface of the parietal cells. This results in an increase in HCl secretion into the stomach lumen.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because HCl secretion in the gastric phase is not primarily increased by the hormone secretin, which is actually involved in the intestinal phase of gastric secretion.
**Option B:** Incorrect because the hormone somatostatin, which is released by D cells in the pancreas and gastrointestinal tract, actually inhibits gastric acid secretion, not increases it.
**Option C:** Incorrect because the hormone cholecystokinin (CCK), which is released by the duodenum in response to fat and protein, primarily stimulates the release of pancreatic enzymes and bile, but not gastric acid secretion.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the gastric phase of gastric acid secretion is primarily controlled by the release of gastrin, and that the antrum of the stomach plays a crucial role in regulating this process.
**Correct Answer:** D. Gastrin