Pancreatic Exocrine Secretions & Its Control

Question 1

What do acinar cells secrete?

Answer 1

Acinar cells secrete digestive enzymes

Question 2

What do acini form, connect to and empty into?

Answer 2

Acini form sacs/lobule → connect to the ductal tree → empty into duodenum

Question 3

What cells are intercalated ducts made up of?

Answer 3

squamous/cuboidal epithelial cells

Question 4

What cells are intralobular ducts made up of?

Answer 4

cuboidal or low columnar epithelial cells

Question 5

What cells are extralobular ducts made up of?

Answer 5

columnar epithelial cells

Question 6

What cells are interlobular ducts made up of?

Answer 6

columnar epithelial/goblet cells

Question 7

How many litres of fluid is secreted per day by the pancreas and what does it contain?

Answer 7

Secretes 1.5L of fluid/day (containing, e.g. sodium and HCO3–rich juice,
albumin, globulin and digestive enzymes)

Question 8

What do acinar cells secrete and what does it breakdown?

Answer 8

Acinar cells secrete digestive enzymes which breakdown carbohydrates,
fats, proteins, and nucleic acids

Question 9

What form are enzymes secreted in and what does it prevent?

Answer 9

Enzymes secreted in inactive form (as zymogens) to prevent auto-digestion
(of pancreas)

Question 10

Where does activation of enzymes secreted from pancreas occur?

Answer 10

Activation of the enzymes occurs in the duodenum

Question 11

What are the anions secreted in the pancreatic juice?

Answer 11

HCO3-, Cl-, SO42-, HPO42-

Question 12

What are the cations secreted in the pancreatic juice?

Answer 12

Na+, K+, Ca2+, Mg2+

Question 13

What does the HCO3- rich juice from the pancreas help to neutralise?

Answer 13

HCO3–rich juice from the pancreas (and gallbladder)
help to neutralise gastric acid (↑pH to 6 or 7)

Question 14

What modifications occur to the pancreatic juice as it travels through the duct?

Answer 14

• Epithelial cells actively exchange Cl-/HCO3-
• H+ is actively eliminated by Na+/H+ exchanger
• H+ exchanged for K+ - driven by Na+/K+ ATPase
• H+ neutralises HCO3- (H2CO3 formed)
• …… CO2 and HCO3- produced in the blood
• ……. CO2 diffuses in and forms H2CO3 with H2O

Question 15

What are the 3 major types of enzymes secreted from the pancreas?

Answer 15

-Proteolytic enzymes
-Amylase
-Lipase

Question 16

What do proteolytic enzymes digest and what does this put the pancreas at risk at?

Answer 16

Digestion of proteins; so the pancreas is at risk of autodigestion

Question 17

Where are enterokinase enzymes found?

Answer 17

In the brush border of duodenum

Question 18

What is enterokinase secreted in response to?

Answer 18

Secreted in response to CCK

Question 19

What does enterokinase do?

Answer 19

Converts trypsinogen to trypsin

Question 20

What are enterokinase inhibitors of?

Answer 20

Inhibitors of autodigestion

Question 21

What does trypsin activate in acute pancreatitis and what does this cause the formation of and from what substrate?

Answer 21

Trypsin activates phospholipase A2 (PLA2) in the
pancreatic duct
Lecithin–>Isolecithin

Question 22

What does isolecithin so to pancreatic tissue?

Answer 22

disruption of pancreatic tissue, membrane damage &
necrosis

Question 23

what is a good diagnostic test for acute pancreatitis?

Answer 23

↑ [pancreatic α-amylase]blood

Question 24

What enzymes cross the basolateral membrane and what does this suggest?

Answer 24

• Chymotrypsinogen and amylase cross the basolateral membrane of
  pancreas
   Suggests bidirectional permeability of the basolateral membrane to
  digestive enzymes

Question 25

What type of signalling controls secretions of the pancreas?

Answer 25

Neuroendocrine signals

Question 26

What does vagal stimulation do to secretions of the pancreas?

Answer 26

enhances rate of secretion of enzymes and aqueous components of pancreatic juice

Question 27

What does sympathetic stimulation of the pancreas do?

Answer 27

inhibits secretion

Question 28

What does secretin and CCK stimulate secretion of in pancreas?

Answer 28

stimulate secretion of pancreatic fluid

Question 29

What is the control of pancreatic secretions in the cephalic phase and what is stimulated and released?

Answer 29

vagal (ACh and VIP) stimulation of gastrin release from antrum → some enzyme-rich pancreatic juice

Question 30

What is the control of pancreatic secretions in the gastric phase and what is secreted and released?

Answer 30

Distension (vago-vagal reflex on fundus or antrum), amino acid- and peptide- (in antrum)-stimulated gastrin secretion → release of enzyme-rich pancreatic juice

Question 31

What does the vago-vagal reflex release in the gastric phase?

Answer 31

Vago-vagal reflex also causes ACh release

Question 32

What does a vagotomy reduce the response to?

Answer 32

Vagotomy → 50%↓ in response to acidic chyme

Question 33

What is the control of pancreatic secretions during the intestinal phase and what is secreted and released?

Answer 33

secretin and CCK; enteropancreatic reflexes - Acidic chyme in duodenum and jejunum induces the secretion of pancreatic juice (HCO3 - and enzymes)

Question 34

What does secretin from duodenal and jejunum induce?

Answer 34

Induces pancreatic duct cells to secrete HCO3- -rich pancreatic juice, but ↓ enzyme content -Secretin also stimulates production of bile

Question 35

What does CCK stimulate from the duodenal and jejunum?

Answer 35

CCK stimulates pancreatic acinar cells to synthesise and release enzyme- rich pancreatic juice; and stimulates the secretion of concentrated bile for fat absorption

Question 36

What does CCK do the gallbladder and what does this release?

Answer 36

CCK contracts the gallbladder and relaxes the sphincter of Oddi → release of bile and some HCO3- into duodenum

Question 37

What does CCK potentiate and why?

Answer 37

CCK potentiates the effects of secretin, which is a weak agonist of acinar cells