Pancreas (exocrine)

Question 1

what 2 things must happen once the chyme enters the duodenum

Answer 1

1. acid must quickly and efficiently be neutralized to prevent damage
2. macromolecular nutrients must be broken down further

Question 2

duct progression from pancreas

Answer 2

major pancreatic –> common bile –> common excretory duct

empty exocrine secretions into duodenum via the sphincter of Oddi

Question 3

insufficient exocrine supply from pancreas –> leads to what

Answer 3

starvation….regardless of food consumption

Question 4

how much does pancreas secrete

Answer 4

1 L and 6-20 g of protein

Question 5

islet of langerhans

Answer 5

cluster of pancreatic ENDOCRINE cells

Question 6

acini

Answer 6

clusters of exocrine cells in pancreas

Question 7

release of digestive enzymes from acinar cells in pancreas

Answer 7

ACh and CCK bind to receptors on cell surface

• -> (+) IP3 and diacyl glycerol –> (+) Ca2++ in cell –> PKC
• -> exocytosis of enzymes (zygomen granules)

Question 8

path from acinar cell onward of exocrine secretions

Answer 8

acinus cell –> intercalated ducts –> larger and larger intralobular ducts –> interlobular ducts

Question 9

the lumen of the acinus communicates directly with ….

Answer 9

the intralobular ducts…which coalesce into interlobular ducts….and then the major pancreatic duct

epithelial cells of the intralobular ducts project ‘back’ into the lumen of the acinus (centroacinar cells)

Question 10

eventually every interlobular ducts coalesce into 2 pancreatic ducts called…

Answer 10

santorini and wirsung

Question 11

secretion of NaCl and water from pancreatic Acinar celsl

Answer 11

ACh and CCK –> (+) Ca2++ in cell –> activates Cl- channel in apical side

uses Na+ gradient to take up Na, K, 2Cl across basolateral membrane

Na+ and water cross via leaky tight junctions between acinar cells

Na/K pump in basolateral maintains Na+ gradient

Question 12

secretin affect on epithelial pancreatic duct cells

Answer 12

directly stimulates them to secrete HCO3- ions into lumen of pancreatic duct,

with water following via the paracellular route to maintian osmotic equilibrium

increases cAMP in cell –> opens CFTR Cl- channel

Question 13

Cl - channel role in HCO3- secretion by duct cells in pancreas

Answer 13

when these are open –> stimulates adjacent antiporter that exchanges the Cl- ions for HCO3-

Question 14

where is HCO3- secreted in pancreas derived from?

Answer 14

1. taken up across basolateral membrane of the duct cells via the NBC- symporter (Na+/HCO3- cotransporter)
   * *recall that increasing gastric acid secretion results in more HCO3- circulating in blood
2. generated in cell via CA

Question 15

contribution of pancreas secretion by acinar cells

Answer 15

1. digestive enzymes
2. cofactors
   - trypsin inhibitor protein, Co-lipase
3. other proteins

Question 16

contribution of pancreas secretion by duct cells

Answer 16

1. HCO3-

2. water

Question 17

effect of flow rate on HCO3- and Cl- concentration

Answer 17

HCO3- increased

Cl- decreased

so pH increases with flow rate

shifting from high protein fluid –> high volume secretion in which enzymes are present in lower concentrations but higher absolute amounts

Question 18

trypsin and chymotrypsin

Answer 18

pancreatic proteases

secreted inactive

vesicles also have trypsin inhibitor as a safeguard

Question 19

pancreatic lipase

Answer 19

TG –> 2-monoglyceride + 2 fFAs

needs bile salts to efficiently do shit

target for obesity medication (Orlistat, Xenical)

Question 20

amylase

Answer 20

starch –> maltose (a Glu-Glu disaccharide)

Question 21

other pancreatic enzymes

Answer 21

ribonuclease
deoxyribonuclease
gelatinase
elastase

Question 22

enterokinase

Answer 22

activates trypsinogen –> trypsin

embedded in the intestinal mucosa

trypsin then activates chymotrypsinogen

Question 23

carboxypeptidase

Answer 23

can digest proteins down to a single amino acid unlike the pancreatic proteases

Question 24

fatty acids, amino acids in chyme –>

Answer 24

(+) I cells –> CCK –> acinar cells (ACh potentiates) –> enzymes

Question 25

H+ in duodenum –>

Answer 25

(+) S cells –> secretin –> ductal cells (ACh, CCK potentiate) –> HCO3- secretion

Question 26

gastrin and acinar cells

Answer 26

(+) secretion of digestive enzymes

Question 27

phases of pancreatic secretion

Answer 27

1. cephalic
2. gastric
3. intestinal

Question 28

cephalic phase of pancreatic secretion

Answer 28

1. increase in vagal (ACh) activity
   2a. + acinar cells –> increase secretion
   2b. + ductal cells –> increase secretion

very short lived in humans

stimulus = smell, taste, sight

Question 29

gastric phase of pancreatic secretion

Answer 29

1. food in stomach
2. (+) vagus –> (+) gastrin
   3a. M3 activated on acinar cells
   3b. CCK-B activated on acinar cells
3. increase in enzymes

Question 30

intestinal phase of pancreatic secretion (most important phase)

Answer 30

Digestive Products:

1a. vagovagal reflex
1b. I cells stimulated in duodenum

2a. increase ACh
2b. CCK

3a. acinar and duct cells stimulated –> enzymes + HCO3-
3b. acinar cells stimulated –> enzymes

H+ in lumen

1. S cells stimulated in duodenum
2. secretin
3. ductal cells stimulated
4. HCO3- secretion