Exocrine Pancreas B&B

Question 1

what 2 cell types are found in the exocrine pancreas?

Answer 1

1. acinar cells: secrete enzymes + electrolytes (Na+, Cl-)
2. ductal cells: secrete bicarbonate and water to modify fluid

[bicarb needed to neutralize acidic fluid coming from stomach!]

Question 2

how does flow rate alter the content of pancreatic fluid?

Answer 2

low flow (fasting): high Cl-, low bicarb

high flow (post-prandial): low Cl-, high bicarb

however, pancreatic fluid is always isotonic!! (Na+ and K+ always equal to plasma)

Question 3

_____ is the main stimulus from bicarb secretion from the pancreas

Answer 3

secretin: released by S cells of duodenum in response to H+ content

Question 4

_____ is the major hormonal stimulus for release of pancreatic enzymes from acinar cells

Answer 4

cholecystokinin (CCK)

[can also be stimulated via vagovagal reflex]

Question 5

what are the 2 polymers that make up starch? what pancreatic enzyme breaks down starch?

Answer 5

1. amylose
2. amylopectin

alpha-amylase hydrolyzes alpha1-4 linkages

[note, digestion is not complete until brush border via oligosaccharide hydrolases]

Question 6

describe digestion of carbohydrates through the GI tract

Answer 6

mouth: salivary/lingual amylase - inactivated by acidic pH of stomach

small intestine: pancreatic alpha-amylase - breaks down alpha1-4 linkages of starches (amylose, amylopectin)

brush border: oligosaccharide hydrolases - breaks carbs down to monomers, rate-limiting step of carb digestion

Question 7

describe the action of pancreatic lipase

Answer 7

hydrolyzes triglycerides to give mono-glyceride (glycerol + 1 fatty acid) + fatty acids

pancreatic lipase is assisted by colipase

Question 8

what is needed to activate phospholipase A2?

Answer 8

phospholipase A2: hydrolyzes phospholipids, secreted as inactive proenzyme (zymogen)

activated by trypsin

Question 9

what is needed to active trypsinogen to trypsin?

Answer 9

trypsin: digests proteins and also activates ALL other protein enzymes + phospholipase A2

activated by brush border enzyme enterokinase

Question 10

explain “auto-digestion” of acute pancreatitis

Answer 10

blocked secretion of enzymes while synthesis is ongoing = large amounts of trypsin being produced/activated

trypsin can activate other digestive enzymes and also more trypsin, but they’re not being secreted so they start to “auto-digest” the pancreas

Question 11

what labs are used to dx acute pancreatitis?

Answer 11

blocked secretion of enzymes while synthesis is ongoing = elevated serum pancreatic enzyme levels

specifically, elevated amylase and lipase

[lipase is more specific]