What is the role of bicarbonate in pancreatic juice, and which cells secrete it?

• A. Acidifies chyme; secreted by acinar cells.
• B. Neutralizes gastric acid in chyme; secreted by pancreatic ductal cells.
• C. Buffers bile; secreted by hepatocytes.
• D. Acts as a digestive enzyme; secreted by goblet cells.

Answer: (B)

Bicarbonate in pancreatic juice serves to neutralize the acidic chyme as it enters the small intestine, creating an alkaline environment in which the digestive enzymes can work effectively. This bicarbonate is secreted by the pancreatic ductal cells, not the acinar cells. The process is driven by secretin, released by the duodenum in response to stomach acid, which stimulates these ductal cells to pour bicarbonate into the duct lumen. This bicarbonate-rich juice also protects the intestinal lining from irritation by acid and provides the right pH for enzymes like amylase, lipase, and proteases to function. The other options don’t fit: bicarbonate isn’t used to acidify chyme, isn’t produced by hepatocytes, isn’t an enzyme, and isn’t secreted by goblet cells.