Question

As food is moved through the digestive tract the pancreas and small intestine release digestive enzymes according to signals based on contents of the duodenum. Briefly describe the stimuli that trigger secretion of enzymes from exocrine cells of the pancreas and small intestinal mucosa. You should briefly describe how they are similar, and how they differ.

Answer 1

As the food moves through the gastrointestinal tract, and when it reaches the duodenum via the stomach, the food or the paste, that is, chyme becomes acidic because of the presence of acid in the stomach. When this acidic chyme moves towards the first section of the duodenum, it results in the discharging of cholecystokinin and secretin from the duodenal mucosa, which further instigates the pancreas to discharge alkaline pancreatic juice that comprises pancreatic enzymes and bicarbonate ions.

Now the bicarbonate ions will turn the chyme alkaline and is now known as chyle. It is made alkaline as the pancreatic enzyme needs alkaline pH to function on food. The intestinal juice is also secreted due to the discharging of similar hormones as mentioned above. However, the difference is that both the mechanical stimulus and nervous stimulus results in the discharging of intestinal juice, though it is not true for pancreatic juice.