Digestive 1.3: Pancreas

Question 1

Exocrine secretion on blood and lumen side

Answer 1

Côté sanguin: symport Na-K-2Cl
(brings in Cl-)

Cl- sécrété dans lumière via 2 canaux: CFTR et canaux Cl-
CFTR is a symporter that releases HCO3- and Cl-
with chlore release = ALWAYS WATER AND SODIUM RELEASE TO MAINAINT OSMOLARITY

Question 2

Mutations in what secretory canal can cause pancreatic deficency?

Answer 2

Cystic Fibrosis -> CFTR is affected in this disease

Question 3

What is the origin of HCO3- in the pancreas?

Answer 3

HCO3- provient de:
Côté sanguin: symport Na+/2HCO3-
Cytoplasme: via anhydrase carbonique

Question 4

In a patient affected with CFTR deficency, what could you perscribe to help?

Answer 4

A secretin agonist
Stimulation d’activité de CFTR par sécrétine

Question 5

Why would you need HCO3- released in the pancreas?

Answer 5

The presence of HCO3- is key because enzymes pancréatiques actives à pH = 7-8

Si défaut de sécrétion HCO3-: pH trop acide → Maldigestion et malabsorption

Question 6

Mode of action of secretin vs CCK and their effect.

Answer 6

Secretin targets CFTR (only)
As such, secretin will augmente sécrétion HCO3- et diminue Cl-

On the other hand, CCK targets all channels
CCK will result in increased Cl- and HCO3-

Question 7

What are the 3 pancreatic enzymes?

Answer 7

PROTÉASES, AMYLASE et LIPASE

Question 8

What is particular about proteases in the pancreas?

Answer 8

Risque d’autodigestion: MUST BE SECRETED in forme inactive pro-enzyme otherwise they will digest the pancreas

Question 9

Where and how are proteases activated?

Answer 9

get activated at the duodenum (Trypsinogène)

first step involves activation of TRYPSINE

TRYPSINE can auto activate and activate other non-active proteases

Question 10

What is Entérokinase ?

Answer 10

Kinase in the intestins that activates trypsinogene into trypsin

Question 11

What hormone stimulates release of trypsinogene?

Answer 11

CCK stimulates the release of trypsinogène

Question 12

You patient is worried of taking a CCK agonist in the fear that there is no way to stop the accumulation of hormones that it will trigger. What should you explain him?

Answer 12

CCK stimulates trypsinogene which eventually leads to more trypsine
I understand the worry, however,TRYPSINE also has an auto-regulation role so no danger

Question 13

True or False,
In contrast to proteases, amylases (glucose digestion enzymes) can be secreted in their active form beta amylase

Answer 13

FALSE

Yes, amylases are secreted in active form becasue they are not dnagerous but it is
alpha-amylase

Question 14

Enzyme important for the digestion of lipids

Answer 14

Lipase

Question 15

A patient presents with high fat in his blood. The chief doctor tells you that there is no problems with his pancreas but the problem is enzymatic. What is the issue?

Answer 15

1. The enzyme lipase is responsible for breaking down fat
2. Because there are no problems with pancreas -> lipase is being released just fine
3. Lipase requires co-lipase in order to bind micelle and excert function
4. It could be that the patient has low levels of co-lipase
5. Trypsin is what activates co-lipase
6. Because the pancreas is releasing fine, then the issue could be with the duodenum so likely -> entérokinase

Question 16

What are 5 ways the pancreas defends itself from auto-digestion. Which of these is affected in cystic fibrosis?

Answer 16

The enzymes are kept safe inside granules impermeables
Some of the enzymes are created as innactive
activation happens in the duodenum
creation of inhibitors of enzymatic activity (in case there is an activated pro-enzyme)
Constant flow to assure that enzymes do not collect
this is affected by cystic fibrosis