Which part of the digestive system releases pepsin (as pepsinogen) into the lumen?

• A. Gallbladder
• B. Liver
• C. Pancreas
• D. Stomach (gastric glands, chief cells)

Answer: (D)

Verified step by step guidance

1. Understand that pepsin is an enzyme responsible for breaking down proteins in the digestive system, and it is initially secreted in an inactive form called pepsinogen to prevent self-digestion.
2. Identify the location where pepsinogen is secreted: it is released by the chief cells found in the gastric glands of the stomach lining.
3. Recognize that the gallbladder stores bile, the liver produces bile, and the pancreas secretes digestive enzymes into the small intestine, but none of these release pepsinogen.
4. Recall that once pepsinogen is secreted into the stomach lumen, it is activated to pepsin by the acidic environment created by hydrochloric acid from parietal cells.
5. Conclude that the stomach, specifically the gastric glands' chief cells, is the part of the digestive system responsible for releasing pepsinogen into the lumen.