L21: The Exocrine Pancreas

Question 1

the pancreas consists of what 2 types of glandular tissue

Answer 1

• islets within parenchyma of glands (endocrine fxn)
• exocrine glands (digestive enzymes)

Question 2

pancreatic juice is rich in _____ and ______ and is secreted into the lumen of acini and modified on its way through the ducts

Answer 2

digestive enzymes and bicarbonate

Question 3

pancreatic fluids drain where

Answer 3

into SI

Question 4

what are the functions of pancreatic juice

Answer 4

• neutralize acids from stomach when food enters duodenum pH changes dramatically
• provide enzymes for the digestion of food (amylases, lipases, proteases)

Question 5

what enzymes break down glucose polymers

Answer 5

amylases

Question 6

what enzymes digest triglycerides, phospholipids and cholesterols

Answer 6

lipases

Question 7

what enzymes break down proteins into amino acids, di/tri and oligopeptides

Answer 7

proteases

Question 8

what is ecbolic secretion

Answer 8

protein secretion by acinar cells

Question 9

what cells secrete the aqeous portion of pancreatic juice (electrolytes, bicarbonate, water)

Answer 9

centroacinar and ductal cells
= hydroelatic secretion

Question 10

hydroelatic secretion

Answer 10

alkaline and watery secretion by duct cells

Question 11

what is pancreatic bicarbonte secretion into the SI necessary for

Answer 11

neutralization of gastric acid emptied into SI

Question 12

Bicarbonate is released via a chloride bicarbonate exchanger that is driven by…

Answer 12

the gradient for bicarbonate

Question 13

the composition of pancreatic juice depends on ?

Answer 13

rate of secretion (flow rate)
at low flow - Cl- is main anion
at high flow, HCO3 concentration increases

Question 14

elevated levels of _____ stimulate flow rate of pancreatic juice, causing a change in the composition of the fluid

Answer 14

secretin

Question 15

what things regulate pancreatic secretion

Answer 15

• CCK and gastrinstimulate acinar cells to secrete proenzymes
• Secretin stimulates duct cells to secrete water and bicarbonate
• vagal input stimulates acinar and duct cells

Question 16

2 ____ and one _____ control mechanisms stimulate pancreatic secretion

Answer 16

hormonal
neural

Question 17

vagal input (Ach) stimulates what cells

Answer 17

acinar and duct cells

Question 18

CCK and gastrin stimulate what cells

Answer 18

acinar, to secrete proenzymes

Question 19

secretin stimulates what cells

Answer 19

duct cells, to secrete water and bicarbonate

Question 20

pancreatic secretion occurs in what 3 phases

Answer 20

• cephalic
• gastric
• intestinal

Question 21

what is the most important phase of pancreatic secretion and why

Answer 21

intestinal phase; it controls 80% of pancreatic secretion

Question 22

during the intestinal phase of pancreatic secretion, _____ is released from ___ cells in response to fats and amino acids in the duodenum

Answer 22

CCK, I-cells
CCK enters circulation and stimulates acinar cells

Question 23

during the intestinal phase of pancreatic secretion, _____ is released from ____cells in response to peptides and AA in stomach

Answer 23

gastrin

Question 24

during the intestinal phase of pancreatic secretion, in response to a low pH in the duodenum, ______ is released from ____ cells and stimulates duct cell secretion

Answer 24

secretin
S cells

Question 25

peptide hormone synthesized and relased by entero-endocrine I cells

Answer 25

CCK

Question 25

where are I cells present

Answer 25

dudoenum, jejunum, ileum

Question 26

what are the stimulators for I-cells (CCK) ; what do I cells target

Answer 26

released when fatty acids and amino acids enter duodenum target: acinar cells

Question 27

what organs does CCK act on

Answer 27

* gallbladder --> contractions * pancreas --> acinar secretion * stomach --> reduced emptying * sphincter of bile/pancreatic duct --> relaxation

Question 28

peptide hormone synthesized & released by entero-endocrine 'S cells'

Answer 28

secretin

Question 29

where can S cells be found

Answer 29

duodenum

Question 30

what is the stimulator for S cells and what do S cells target

Answer 30

low pH (<4.5) in the duodenum target: Duct cells

Question 31

what phases of pancreatic secretion share regulation by the vagal pathway

Answer 31

cephalic and gastric

Question 32

pancreatitis occurs when...

Answer 32

digestive enzymes are activated upon release into the pancreatic duct system which causes autophagy and inflammation

Question 33

an **inflammation of the pancreas** with histological presence of **edema, neutrophilic infiltrate and necrosis**

Answer 33

pancreatitis

Question 34

what can cause pancreatitis

Answer 34

* obstruction causing impaired flow in pancreatic ducts - zymogen granules and proenzymes get trapped in ducts and prematurally activate * spontaneous trypsinogen cleavage overwhelming the trypsin inhibitor causing premature activation of trypsin

Question 35

why does pancreatitis cause malabsorption and maldigestion causing anorexia, lethargy, exercise intolerance/weakness, V/D+, abdominal pain, dehydration, fever, arrythmia (caused by electrolyte imbalance)

Answer 35

due to a lack of enzymatic activity

Question 36

what is the key factor in initiating pancreatic inflammation

Answer 36

activation of trypsin within the acinar cells

Question 37

pancreatic lipases ______ lipids (triglycerides) which are used for long term energy storage

Answer 37

hydrolyze

Question 38

triglycerides are apolar and have to be converted into _____ in order to be transported

Answer 38

glycerol, monoglycerides, diglycerides, fatty acids

Question 39

what cells produce pancratic lipases

Answer 39

pancreatic acinar cells

Question 40

what proteins maintain the bicarbonate gradient

Answer 40

* Na HCO3 cotransporter * intracellular carboanhydrase (CA) * Na-K ATPase * Na-H exchanger * proton pump * chloride channel + exchanger

Question 41

digestive enzymes are activated and work best in an ______ environment

Answer 41

alkaline

Question 42

what are the 4 types of pancreatic digestive enzymes

Answer 42

proteases amylolytic enzyme lipases nucleases

Question 43

where are digestive enzymes activated

Answer 43

in the **intestinal lumen of the duodenum**

Question 44

what enzyme converts inactive trypsinogen into active trypsin which is then able to activate other proenzymes

Answer 44

enterokinase

Question 45

what is the function of protease inhibitors in the zymogen granule

Answer 45

blocks the action of prematurely activated enzymes

Question 46

what is the function of nondigestive proteases

Answer 46

they degrade active enzymes