Answer :
Final answer:
A drop in pH below 4.5 in the duodenum stimulates the secretion of pancreatic juice, facilitated by the hormones secretin and cholecystokinin (CCK).
Explanation:
A drop in pH below 4.5 in the duodenum stimulates the secretion of pancreatic juice. This is due to the hormone secretin, which is released when the acidic chyme from the stomach enters the duodenum. Secretin prompts the pancreas to produce a bicarbonate-rich alkaline solution to neutralize the acidity.
Another hormone involved is cholecystokinin (CCK), which stimulates the pancreas to secrete enzyme-rich pancreatic juice and also prompts the gallbladder to release bile into the duodenum, aiding in digestion.