The primary role of the chief cells in gastric physiology is to secrete what substance?

The primary role of chief cells in gastric physiology is to secrete pepsinogen, which is an inactive precursor of the enzyme pepsin. Pepsinogen itself is a zymogen, meaning that it must be activated to function as an enzyme. Once pepsinogen is secreted into the stomach lumen, it is converted to pepsin in the presence of the acidic environment created by gastric acid (hydrochloric acid) secreted by parietal cells. Pepsin plays a crucial role in the digestion of proteins, facilitating their breakdown into smaller peptides.

While other substances such as insulin, gastrin, and amylase are important in various physiological processes, they are not secreted by chief cells. Insulin is produced by beta cells in the pancreas, gastrin is a hormone secreted by G cells in the gastric mucosa that stimulates acid secretion, and amylase is an enzyme primarily secreted by the salivary glands and pancreas for carbohydrate digestion. Thus, the function of chief cells is specifically associated with the secretion of pepsinogen.