Secretion in the pancreas and intestines

Question 1

Describe some of the functions of the pancreas

Answer 1

Produces enzymes for digestion of nutrients
Achieving optimum pH in small intestine
Regulates fed and fasted states

Question 2

What is the pancreas divided into?

Answer 2

Lobules

Question 3

Describe the network of ducts in the pancreas

Answer 3

Lobules drain into intralobular ducts, into interlobular ducts and into a main duct

Question 4

What does the pancreatic duct merge with?

Answer 4

The bile duct

Question 5

Where do the pancreatic products enter the duodenum?

Answer 5

Duodenal papilla

Question 6

What controls secretion into the duodenum?

Answer 6

The sphincter of Oddi

Question 7

What is the functional secretory unit of the pancreas?

Answer 7

An acinus
(and a small intercalated duct)

Question 8

What makes up an acinus?

Answer 8

A cluster of acinar cells

Question 9

What do acinar cells secrete?

Answer 9

Zymogens
Digestive enzymes
Isotonic plasma-like fluid

Question 10

How are acinar cells specialised for their role?

Answer 10

Large number of RER and secretory vesicles

Question 11

What is a centroacinar cell?

Answer 11

The cells at the junction of the duct cells and acinar cells

Question 12

What do goblet cells do?

Answer 12

Produce mucus

Question 13

What is the purpose of mucus?

Answer 13

Lubrication
Hydration
Mechanical protection
Immunological role

Question 14

How are acinar cells stimulated?

Answer 14

Through CCK and muscarinic acetylcholine receptors

Located on the basolateral cell membrane

Question 15

What pathway leads to secretion from an acinar cell?

Answer 15

Phospholipase C (PLC/PKC)/Ca2+ signal-transduction pathway

Question 16

What is the second method of activating an acinar cell?

Answer 16

VIP and secretin activate adenylyl cyclase, leading to the production of cAMP and the activation of PKA

Question 17

What is the primary function of the pancreatic duct cell?

Answer 17

Secrete HCO3- that alkalinises and hydrates the enzymes secreted by the acinar cells

Question 18

What stimulates pancreatic duct cells?

Answer 18

Secretin (mainly)

Ach (a little)

Question 19

By what method is HCO3- secreted?

Answer 19

A HCO3-/Cl- exchanger

Question 20

Which anion channel allows Cl- to diffuse into the lumen?

Answer 20

The cystic fibrosis transmembrane conductance regulator (CFTR)

Question 21

What produces secretin?

Answer 21

S cells

Question 22

What is secretin produced in response to?

Answer 22

Duodenal acidification

Question 23

What problems may someone with cystic fibrosis encounter in the pancreas?

Answer 23

Faulty CFTR channels
Decreased secretion of HCO3- and water by the pancreas
Ductal obstruction and pancreatic tissue destruction

Question 24

What role does CCK play in pancreatic secretion?

Answer 24

CCK stimulates acinar cells to increase protein secretion

It is produced by duodenal I cells in response to fatty food

Question 25

What inhibits pancreatic secretion?

Answer 25

Somatostatin

Question 26

How does somatostatin inhibit pancreatic secretion?

Answer 26

Inhibits the release of CCK and secretin

Question 27

Name the phases of pancreatic secretion

Answer 27

Cephalic phase Gastric phase Intestinal phase

Question 28

Describe the cephalic phase of pancreatic secretion

Answer 28

Accounts for 25% | Mediated by Ach

Question 29

Describe the gastric phase of pancreatic secretion

Answer 29

Accounts for 10-20% Gastrin mediated (gastrin is a weak CCK agonist) Neural pathways via gastric distension

Question 30

Describe the intestinal phase of pancreatic secretion

Answer 30

Accounts for 50-80% Chyme enters the duodenum Gastric acid triggers secretin to be produced Lipids stimulate CCK production

Question 31

How does the pancreas prevent autodigestion?

Answer 31

Zymogens only become activated after coming in contact with the small bowel enzyme enterokinase Secretory granule membrane is impermeable to proteins Enzyme inhibitors are also present in the secretory granules pH and ionic conditions limit activity

Question 32

What may cause acute pancreatitis?

Answer 32

``` Gallstones Ethanol Trauma Steroids Mumps Autoimmune Scorpion sting Hypercalcaemia ERCP Drugs ```

Question 33

What symptoms are characteristic of acute pancreatitis?

Answer 33

Abdominal pain (epigastrium and radiates to the back) Serum amylase and/or lipase >3 times the upper limit of normal CT scan

Question 34

How many stages of acute pancreatitis are there?

Answer 34

3

Question 35

Describe phase 1 of acute pancreatitis

Answer 35

Premature activation of trypsin within pancreatic acinar cells

Question 36

Describe phase 2 of acute pancreatitis

Answer 36

Intra-pancreatic inflammation

Question 37

Describe phase 3 of acute pancreatitis

Answer 37

Extra-pancreatic inflammation Systemic sepsis Multiple organ failure

Question 38

How is acute pancreatitis treated?

Answer 38

Resting the pancreas with IV fluids Pain relief Therapeutic Endoscopic Retrograde Cholangiopancreatography

Question 39

What is chronic pancreatitis?

Answer 39

Chronic pancreatitis is inflammation of the pancreas that does not heal or improve

Question 40

What is the most common cause of chronic pancreatitis?

Answer 40

Chronic alcohol abuse