Step 1: Understanding the Problem:
The endocrine cells of the gastrointestinal tract secrete several peptide hormones (like Gastrin, Secretin, CCK, and GIP) that regulate the complex processes of digestion.
Step 2: Approach and Formula:
Identify the specific target organ and the resulting primary secretions stimulated by the gastrointestinal hormone Gastrin.
Step 3: Detailed Explanation:
- Gastrin: Acts primarily on the gastric glands located in the stomach wall. It strongly stimulates the secretion of gastric juice, which is largely composed of Hydrochloric acid (HCl) and the proenzyme pepsinogen.
- Secretin: Acts on the exocrine pancreas, stimulating the secretion of water and bicarbonate ions.
- Cholecystokinin (CCK): Acts on both the pancreas and gall bladder, stimulating the release of pancreatic enzymes and bile juice, respectively.
Based on these distinct functions, Gastrin is responsible for HCl and pepsinogen.
Step 4: Final Answer:
Gastrin stimulates the secretion of Hydrochloric acid and pepsinogen.