Final answer:
The liver, gallbladder, and pancreas secrete chemicals into the pancreatic duct for the digestion process in the duodenum, with secretin and cholecystokinin hormones regulating the secretion of bicarbonate and digestive enzymes.
Step-by-step explanation:
The organs that secrete chemicals into the pancreatic duct to act on the duodenum are the liver, the gallbladder, and the pancreas itself. When acidic chyme enters the duodenum, it triggers the pancreas to produce an alkaline bicarbonate solution, which is crucial for neutralizing the stomach acid.
This response is stimulated by a hormone called secretin. Alongside secretin, the presence of proteins and fats in the duodenum prompts the secretion of another hormone called cholecystokinin (CCK), which encourages the pancreas to release enzyme-rich pancreatic juices and stimulates the gallbladder to release bile. The liver produces bile which is then delivered to the duodenum directly or stored in the gallbladder before being released. Together, these enzymes and bile facilitate the digestive process by breaking down carbohydrates, proteins, lipids, and nucleic acids.