GI - Pancreas, Liver

Question 1

pancreatic secretory structure

Answer 1

digestive enzymes mad ein acinar cells

ductal cells modify filtrate

Question 2

pancreatic acinar cells secrete

Answer 2

proteases (zymogens): trypsinogen, chymotrypsinogen, procarboxypeptiddase, proelastase
pancreatic amylase
lipases: pancreatic lipase, carboxyl ester lipase, colipase, phospholipase A

Question 3

pancreatic protection from autodigestion

Answer 3

secrete zymogens that are activated in intestines by membrane bound enterokinase
also secrete trypsin inhibitor

Question 4

activation of zymogens in SI

Answer 4

enterokinase activates trypsinogen to trypsin

trypsin activates chymotrypsinogen, procarboxypeptidase and trypsinogen

Question 5

how do active enzymes in SI become inactivated

Answer 5

bacteria

Question 6

things that stimulate pancreatic acinar cell secretion

Answer 6

CCK*
ACh
secretin

Question 7

pancreatic potentiation

Answer 7

CCK + ACh = additive

CCK + secretin = potentiation

Question 8

pancreatic potentiation cause

Answer 8

CCK/ACh use Ca as secondary messenger

secretin use cAMP as secondary messenger

Question 9

neuronal stim of pancreatic secetions

Answer 9

thought/chew –> vagal and enteric stim acinar/duct (cephalic)
vagovagal/gastropancreatic
distention –> reflexes stim acinar/duct (gastric)

Question 10

hormonal stim of pancreatic secretions

Answer 10

acid in SI –> secretin stim duct cells
AA/FA in SI –> CCK stim vagovagal reflexes to acinar/duct
distention/hypertonicity –> enteropancreatic reflexes stim acinar/duct

Question 11

Cystic fibrosis transmembrane conductance regulator (CFTR)

Answer 11

shuttles Cl from duct cell into lumen

makes gradient for HCO3 exchange (HCO3 into lumen)

Question 12

most powerful regulator of HCO3 secretion

Answer 12

secretin

Question 13

results of CFTR

Answer 13

liquify protein rich secretion of acinar cells (Cl brings in water)
keep pancreatic proenzymes inactive (alkaline)

Question 14

importance of CFTR

Answer 14

if don’t dilute protein secretion ducts become blocked

destroy pancreatic tissue, replace with fibrotic tissue

Question 15

things that cause pancreatitis

Answer 15

alcohol abuse
hepatotoxic drugs
microorganisms

Question 16

results of pancreatitis

Answer 16

swelling –> compresses panc duct –>. retention of panc secretions –> digestion of panc tissue

Question 17

liver fxns

Answer 17

intermediary metabolism (for other organs)
metabolize drugs
synthesize plasma proteins
store glycogen, fat, Fe, Cu, vit A, D, B12
activation of vit D
excretion of CHL/bilirubin
fat digestion

Question 18

hepatic portal vein carries

Answer 18

carry venous blood draining the digestive tract

Question 19

hepatic portal vein fxn

Answer 19

processes/stores newly absorbed nutrients

Question 20

hepatic portal vein structure

Answer 20

branches repeatedly, forming smaller venules –> sinusoids

Question 21

hepatic artery carries

Answer 21

arterial blood

Question 22

hepatic artery fxn

Answer 22

provide liver O2 supply and metabolites for hepatic processing (25%)

Question 23

hepatic artery structure

Answer 23

branches –> arterioles –> capillaries –> sinusoids

Question 24

liver lobule structure

Answer 24

hexagonal arrangements of tissue around central vein
3 vessels @ periphery (hepatic artery, portal vein, bile duct)
sinusoids empty into central vein –> hepatic vein

Question 25

hepatocytes

Answer 25

60% of cell production

responsible for most synthetic/metabolic fxns of liver

Question 26

hepatocyte structure

Answer 26

arranged inplates 1 cell thick (increase SA)

polarized: basolateral (sinusoidal) and apical (canalicular) domains

Question 27

stellate (Ito) cells

Answer 27

fat-storing cells
contain vitamin A
transformed to myofibroblasts following injury (can secrete collagen into the sinusoids)

Question 28

bile composition

Answer 28

excretory: bilirubin, drug metabolites, CHL
secretory: bile, HCO3

Question 29

making bile

Answer 29

primary bile acids (synthesized from CHL)
conjugated w/ glycine/taurine, secreted as a Na salt –> more soluble
secondary bile acid made by bacteria in SI by dehydroxylation

Question 30

bile fxn

Answer 30

emulsify fat droplets
increase SA for digestive enzymes
eliminate excess CHL (solubilize)
facilitate absorption of fat-soluble vitamins

Question 31

how bile works

Answer 31

bile particle has a hydrophobic and hydrophilic part
hydrophobic inserts in fat, hydrophilic stays outside
form tiny balls that repel each other

Question 32

gall stones

Answer 32

gallbladder stores bile - if CHL isn’t soluble enough it precipitates –> gall stones

Question 33

sphincter of Oddi

Answer 33

@ common bile duct/SI jxn

open @ meal time

Question 34

CCK and gallbladder

Answer 34

stim gallbladder to contract

relax sphincter of Oddi

Question 35

secretin and gallbladder

Answer 35

stimulate secretion of HCO3

Question 36

how does liver know its meal time

Answer 36

recovered bile (2/3 of total) return to liver in portal circulation

Question 37

de novo bile salt synthesis

Answer 37

when bile is returned, liver knows its meal time (@ meal time use only recycled bile salts)
when no bile returned, liver knows its no longer meal time (then use all de novo)

Question 38

bile salts – liver feedback

Answer 38

positive feedback: bile salts in portal blood stimulates rate of secretion by liver
negative feedback: bile salts in portal blood inhibits the synthesis of new bile acids by liver

Question 39

age changes in liver

Answer 39

repair of damaged cells is slower
ability to withstand stress goes down
down blood flow
down drug metabolism (up half life, side effects)
down production/flow of bile

Question 40

age changes to pancreas

Answer 40

pancreatic ductal hyperplasia, fibrosis
down enzyme secretion
down bile salt synthesis (liver)
down potential for fat digestion