1. Which of the following primarily stimulates the secretion of hydrochloric acid (HCl) in the stomach?

• A. Cholecystokinin (CCK)
• B. Secretin
• C. Gastrin
• D. Pepsinogen

Answer: (C)

Verified step by step guidance

1. Understand the role of hydrochloric acid (HCl) in the stomach: HCl is secreted by parietal cells in the gastric lining and plays a critical role in digestion by denaturing proteins and activating pepsinogen into pepsin.
2. Review the function of gastrin: Gastrin is a hormone secreted by G cells in the stomach lining. It primarily stimulates parietal cells to secrete HCl and promotes gastric motility.
3. Compare the roles of other options: Cholecystokinin (CCK) primarily stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder, while secretin regulates the secretion of bicarbonate from the pancreas to neutralize stomach acid. Pepsinogen is an inactive precursor to pepsin and is activated by HCl, but it does not stimulate HCl secretion.
4. Identify the correct answer: Gastrin is the primary hormone responsible for stimulating HCl secretion in the stomach, as it directly acts on parietal cells.
5. Conclude the reasoning: Based on the physiological roles of the options provided, gastrin is the correct answer because it directly stimulates the secretion of hydrochloric acid in the stomach.