GI secretions: liver and pancreas Flashcards
Which hormone stimulates the relaxation of the sphincter of Oddi?
CCK-PZ
What is the Ampulla of Vater?
The little prominence where the common bile duct enters the duodenum. Opened and closed by the sphincter of Oddi.
Where is cholecystokinin produced and what stimulates its production?
Duodenal I cells. Stimulated by fatty acids and amino acids.
What is the first target of cholecystokinin? Is it paracrine or endocrine?
Vagal afferent terminals, gallbladder. Paracrine and endocrine.
Where is secretin produced and what stimulates its production?
Duodenal S cells. Stimulated by acid in SI.
What is the first target of secretin? Is it paracrine or endocrine?
Vagal afferent terminal, pancreatic duct cells, cholangiocytes. Paracrine and endocrine.
Where is motilin produced and how is its production stimulated?
Throughout intestine. Stimulated by fasting and neurally.
What is the function of motilin?
Increase GI motility.
What is the source of vasoactive intestinal peptide?
Nerve terminals.
What are the targets of vasoactive intestinal peptide?
Smooth muscle cells, secretory cells.
What are the main effects of cholecystokinin-pancreozymin (CCK).
Pancreatic secretion and gallbladder emptying.
What stimulates the release of CCK.
Lipids and peptides in the small intestine.
Which cells secrete CCK?
I cells
What stimulates the release of secretin.
Acid in the small intestine. Secreted by S cells.
What are the main effects of secretin?
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.
Which organ synthesises bile?
Liver
What charge does bile carry?
Negative charge - more anions than cations.
From what compound are bile salts synthesised?
Cholesterol
What is a bile salt?
A bile acid conjugated with an amino acid (glycine or taurine).
Describe the secretions of hepatocytes.
Bile acids, phosphatidylcholine, conjugated bilirubin and xenobiotics.
What compounds are added to bile as it passes through the bile duct?
Bicarbonate, salt and water.
What process reduces the risk of Ca2+ precipitation in the gallbladder?
Net proton secretion acidifies the bile, reducing the risk of precipitation of Ca2+ (and other) salts. This reduces the risk of gallstones
Are salt and water reabsorbed from the gallbladder?
Yes - concentrates contents of gallbladder so more secretions can be stored in a smaller space.
Why does the pancreas need trypsin inhibitors?
If trypsin became active in the pancreas it would cause autodigestion.
What stimulates pancreatic duct secretion?
Strongly stimulated by secretin. This is potentiated by CCK (via vagus).
Describe the role of the CFTR protein in the pancreatic duct.
CFTR transports Cl- into the lumen where it is then co-transported (via antiporter) with bicarbonate.
