Pancreatic Exocrine Secretions and its Control

Question 1

Steatorrhoea is characterised by the voiding of oily, smelly faeces. The defective secretion of which pancreatic enzyme can cause steatorrhoea?

Answer 1

pancreatic lipase

Question 2

The acinus is a basic unit of the pancreas that has tubuloacinar glands which secrete digestive enzymes. Name 2 digestive enzymes of the pancreas

Recall the table with the names of pancreatic enzymes and the substrates they act on

Answer 2

Trypsin
Pancreatic lipase
Elastase
Chymotrypsin
Colipase
Carboxypeptidases

Question 3

Which of the following is important for the secretion of digestive enzymes from the pancreas?

Answer 3

CCK

Question 4

Secretin acts on the pancreas to promote the secretion of pancreatic juice. Name one of the exocrine secretions of the pancreas whose secretion is increased by secretin

Answer 4

The main answer here is HCO3-. There are others (Na+ - quite a bit of this in the bulk of the secretions; Cl- - not much at all, if anything it goes down actually especially when the pancreas is stimulated to increase its exocrine secretions upon secretin dosing; some K+ and albumin), but they are not as significant. So these should not form part of any serious answer.

You will know this to be true if you try to recall the graph on the effects of secretin on pancreatic secretions. See quiz

Question 5

The cephalic, gastric and intestinal phases are the three main triggers for the control of pancreatic secretions. For each trigger, briefly describe their regulatory effects on the secretion of pancreatic juices.

Answer 5

Cephalic phase- vagal innervation stimulates gastrin release from antrum and this is known to stimulate the secretion of protein-rich pancreatic juice. ACh and VIP are important mediators here –they bring about coordinated contractions and relaxations of gut, respectively.

Gastric phase – distension of stomach (vagal innervation) and contents of the chyme (amino acids, peptides) stimulate gastrin-mediated acid secretion and with it pancreatic juice

Intestinal phase – quantitatively the most important as far as secretion of pancreatic juices are concerned. Two key players: 1) secretin – stimulates ↑ HCO3-rich pancreatic secretions, with less enzyme content; 2) CCK (secreted due to presence of peptides, amino acids, fatty acids in the duodenum and jejunum. CCK is a potent stimulator of the acinar cells to secrete enzyme-rich pancreatic secretions; CCK also pharmacoenhances the effects of secretin on the acinar cells in terms enzyme secretions- secretin is a less potent stimulator of the acinar cells.

Also note that both secretin and CCK have stimulatory effects on the secretion of bile into the duodenum.

Question 6

What is the effect of sympathetic stimulation on the exocrine secretions of the pancreas?

Answer 6

Sympathetic stimulation inhibits the exocrine secretions of the pancreas. Recall that the sympathetic nervous system inhibits digestion

Question 7

Which of the following exocrine secretions of the pancreatic reaches the small intestine at higher levels?

Answer 7

Amylase