GI secretions: liver and pancreas

Question 1

Which hormone stimulates the relaxation of the sphincter of Oddi?

Answer 1

CCK-PZ

Question 2

What is the Ampulla of Vater?

Answer 2

The little prominence where the common bile duct enters the duodenum. Opened and closed by the sphincter of Oddi.

Question 3

Where is cholecystokinin produced and what stimulates its production?

Answer 3

Duodenal I cells. Stimulated by fatty acids and amino acids.

Question 4

What is the first target of cholecystokinin? Is it paracrine or endocrine?

Answer 4

Vagal afferent terminals, gallbladder. Paracrine and endocrine.

Question 5

Where is secretin produced and what stimulates its production?

Answer 5

Duodenal S cells. Stimulated by acid in SI.

Question 6

What is the first target of secretin? Is it paracrine or endocrine?

Answer 6

Vagal afferent terminal, pancreatic duct cells, cholangiocytes. Paracrine and endocrine.

Question 7

Where is motilin produced and how is its production stimulated?

Answer 7

Throughout intestine. Stimulated by fasting and neurally.

Question 8

What is the function of motilin?

Answer 8

Increase GI motility.

Question 9

What is the source of vasoactive intestinal peptide?

Answer 9

Nerve terminals.

Question 10

What are the targets of vasoactive intestinal peptide?

Answer 10

Smooth muscle cells, secretory cells.

Question 11

What are the main effects of cholecystokinin-pancreozymin (CCK).

Answer 11

Pancreatic secretion and gallbladder emptying.

Question 12

What stimulates the release of CCK.

Answer 12

Lipids and peptides in the small intestine.

Question 13

Which cells secrete CCK?

Answer 13

I cells

Question 14

What stimulates the release of secretin.

Answer 14

Acid in the small intestine. Secreted by S cells.

Question 15

What are the main effects of secretin?

Answer 15

Main effect is to stimulate bicarbonate secretion by ductal cells in the pancreas and liver. Trophic effect on the pancreas. Modest inhibition on gastric acid production.

Question 16

Which organ synthesises bile?

Answer 16

Liver

Question 17

What charge does bile carry?

Answer 17

Negative charge - more anions than cations.

Question 18

From what compound are bile salts synthesised?

Answer 18

Cholesterol

Question 19

What is a bile salt?

Answer 19

A bile acid conjugated with an amino acid (glycine or taurine).

Question 20

Describe the secretions of hepatocytes.

Answer 20

Bile acids, phosphatidylcholine, conjugated bilirubin and xenobiotics.

Question 21

What compounds are added to bile as it passes through the bile duct?

Answer 21

Bicarbonate, salt and water.

Question 22

What process reduces the risk of Ca²⁺ precipitation in the gallbladder?

Answer 22

Net proton secretion acidifies the bile, reducing the risk of precipitation of Ca²⁺ (and other) salts. This reduces the risk of gallstones

Question 23

Are salt and water reabsorbed from the gallbladder?

Answer 23

Yes - concentrates contents of gallbladder so more secretions can be stored in a smaller space.

Question 24

Why does the pancreas need trypsin inhibitors?

Answer 24

If trypsin became active in the pancreas it would cause autodigestion.

Question 25

What stimulates pancreatic duct secretion?

Answer 25

Strongly stimulated by secretin. This is potentiated by CCK (via vagus).

Question 26

Describe the role of the CFTR protein in the pancreatic duct.

Answer 26

CFTR transports Cl^- into the lumen where it is then co-transported (via antiporter) with bicarbonate.