Pancreas

Question 1

How many parts of the pancreas are there?

Answer 1

5. Tail, body, neck, head, uncinate process

Question 2

The majority of the pancreas is?

Answer 2

Exocrine acini (secreting digestive enzymes)

Question 3

What do duct cells of the pancreas secrete?

Answer 3

Watery bicarbonate fluid

Question 4

Describe the commonality of the various types of cells in the pancreas

Answer 4

1. Insulin secreting B cells (70%)
2. Glucagon secreting a cells (20%)
3. Somatostatin secreting Delta cells (10%)

Question 5

At what end of the duct are acinar cells located?

Answer 5

At the terminal end.

They secrete low volume, viscous enzymes

Question 6

What is special about centroacinar cells?

Answer 6

They have the properties of acinar cells and duct cells

Question 7

What are the functions of the duct cells?

Answer 7

Modify enzymes released by acinar cells (mobilise/neutralise acid chyme).

Question 8

What connects Duct cells?

Answer 8

Tight junctions

Question 9

Explain the mechanism of duct secretion

Answer 9

1. HCO3- production through carbonic anhydrase. Na moves down gradient via paracellular junction. H20 follows.
2. HCO3- secretion into duct. Cl/HCO3- exchanger. There is a Na/H+ pump at the basolateral membrane to bloodstream.
3. Na management. Na gradient into cell managed by Na/K ATPase pump.

Question 10

Contrast the blood leaving the stomach vs blood leaving pancreas

Answer 10

Stomach = alkaline

Pancreas blood = acidic

Question 11

What enzyme converts trypsinogen into trypsin?

Answer 11

Enterokinase, which is a duodenal brush border enzyme.

Question 12

What does trypsin do?

Answer 12

1. Activates protease zymogens
2. Converts prolipase to lipase.
3. Autocatalyses trypsinogen to trypsin

Question 13

What do proteases (e.g. carboxypeptidase, chymotrypsin) and trypsin do?

Answer 13

Convert longer peptides into shorter peptides

Question 14

How do fats become fatty acids and monoglycerides?

Answer 14

Bile converts fats to triglycerides. Colipase and lipase convert triglycerides into fatty acids and monoglycerides.

Question 15

What can pancreatic autodigestion cause?

Answer 15

Acute pancreatitis

Question 16

Explain hormonal control of bicarbonate secretion.

Answer 16

Decrease in duodenal pH, stimulates secretin from S cells, secretin travels via blood to pancreas, binds to receptors on duct cells, cAMP 2nd messenger increases, Cl channels activated in apical membrane, Cl efflux, increased activity of anion exchanger, HCO3- efflux.

Question 17

Explain how enzyme secretion from acinar cells is controlled.

Answer 17

1. Hormonal. Fats/peptides in duodenum - triggers CCK release (I cells) - CCK travels in blood to pancreas - binds to CCK1 receptors on Acinar cells - PLC/IP3 2nd messenger - increased cytosolic Ca - Zymogen/inhibitor/enzyme granule exocytosed
2. Neural. Vagus nerve releases ACh - binds to muscarinic receptors on Acinar cells - activation of PLC/IP3 2nd messenger, etc

Question 18

What are the 3 phases of pancreatic secretion?

Answer 18

1. Cephalic phase (vagus nerve)
2. Gastric phase - distension of stomach (vagus nerve)
3. Intestinal phase - acid/nutrient detection in duodenum. S cells and I cells.

Question 19

Intestinal phase is mainly mediated by?

Answer 19

HORMONES. Negative feedback loop also present.

Question 20

Majority of secretion is in which phase?

Answer 20

Intestinal phase

Question 21

Acinar cells are activated in all 3 phases of pancreatic secretion. In the intestinal phase, another cell is also activated, which is?

Answer 21

Acinar cells and duct cells

Question 22

CCK and secretin both are the most powerful increasers of HCO3- secretion.

Answer 22

T

Question 23

CCK affects duct cells, but does secretin affect acinar cells?

Answer 23

NO