Physiology: pancreatic secretions

Question 1

Differentiate exocrine and endocrine tissue
Does the pancreas have both exocrine and endocrine functions?
What does each secrete

Answer 1

Exocrine: secretions via ducts; endocrine: ductless secretion, directly into vasculature
Yes
Exocrine: secretes pancreatic fluid
Endocrine: secretes insulin and glucagon

Question 2

What are the 2 components of pancreatic secretions?

Answer 2

Pancreatic juice
Pancreatic enzymes

Question 3

Pancreatic juice:
- What cell type of the exocrine pancreas ducts secrete it?
- What is the main chemical component of pancreatic juice? What is its implications on pH, and thus GI function?

Answer 3

Made by ductal cells
NaHCO3-. Gives slightly alkaline pH of ~8
- Helps neutralise acidic chyme entering the duodenum
- Provides optimal environment for intestinal and pacnreatic enzymes

Question 4

Pancreatic enzymes
- What cell type secretes them?
- What are their two main types (based on activity?)

Answer 4

Acinar cels - specifically, within zymogen granules
Inactive proteolytic enzymes
Active enzymes

Question 5

Inactive proteolytic enzymes:
- Why are they initially inactive?
- Where are they activated?
- 4 examples?

Answer 5

To prevent autodigestion
Small intestine
Trypsinogen, chymotrypsinogen, procarboxypolypeptidase, elastase

Question 6

Active enzymes
- What addition substances are needed for them to function optimally? Where are these found?
- 5 examples?

Answer 6

Bile/ions in the duodenum
Lipase, cholesterol esterase, phospholipase (fats), amylase (carbohydrates), (deoxy)ribonuclease (nucleic acids)

Question 7

Describe how trypsinogen is activated, and its effect on other enzymes

Answer 7

Question 8

What 2 hormones control pancreatic secretions?

Answer 8

Secretin
Cholecystokinin

Question 9

Secretin
- What triggers its release?
- How does it travel?
- What is its target site?
- What is its effect?

Answer 9

When the stomach empties acidic chyme into the duodenum, the mucosa releases inactive secretin - which is activated by the acidic environment

Secretin is absorbed in the blood, and reaches the pancreas to stimulate pancreatic juice production –> NaHCO3- neutralises HCl in chyme

Question 10

Cholecystokinin
- What triggers its release?
- How does it travel?
- What is its target site?
- What is its effect?

Answer 10

Food in the upper GI tract causes the release of CCK from enteroendocrine cells in the duodenum

CCK is absorbed in the blood, causes release of pancreatic enzymes

Question 11

What is the role of the vagus nerve (PNS nerves) in pancreatic secretions?

Answer 11

Increases pancreatic secretions