Bile and the Biliary System Flashcards
4 methods of biliary regulation
Vagus
-weak GB contraction
Bile acids in blood
-lead to parenchymal secretions
Secretin from S cells
- Liver bile secretion
- HCO3 secretion from pancreas
CCK from I cells
- GB contraction
- MDP relaxation
Describe the relationship between bile flow and liver blood flow
Bile secretion is active
As blood flow increases => increased O2 delivery => increased bile flow up to a point
Describe the relationship between biliary pressure and blood pressure
Bile secretion not dependent of hydrostatic pressure gradient
External stimuli => secretion irrespective of pressure grad
Composition of bile
- ions
- others
Na K Ca Cl HCO3
Bile acids FA Bilirubin Cholesterol PL
How is bile acid concentrated
How does this affect the pH
GB side
NaH antiporter
HCO3Cl antiporter
ISS side
NaKATPase
Movement of Na out followed by water => concentrated bile acid
7.5 => 6
Pathway of bile from the liver to the GB
Hepatocytes
Canaliculi
Ductules
Common hepatic duct
Describe the pathway of bilirubin from the liver => circulation
Normal plasma conc
Bilirubin conjugate formed in liver => canaliculi
Conjugate => urobilinogen conjugate by gut flora
Reabsorbed into circulation in terminal ileum
3-10mg/ml
What is jaundice
What are the biliary and non biliary causes
What are the plasma levels of bilirubin in jaundice
Biliary causes
-bile duct blockage (gall stone, cancer)
Non biliary causes
- Increased bilirubin prod (blood related)
- Decreased bilirubin clearance
Plasma levels 18mg/ml
Absorption of lipids and bile salts
Bile emulsifies lipids => increases SA for pancreatic lipase
Bile + FA + glycerol => micelle
Micelle encounters acidic brush border of jejunum => FA + G diffuses into epithelium
Bile salts reabsorbed passively/AT in terminal ileum
Some lost in faeces
Reesterification of lipid
Micelle contents converted to TAG, PL, CE in SER
Apo synthesized in RER => enters SER and associates with TAGs
Chylomicrons formed from Golgi leave epithelium via exocytosis => lacteal
Chylomicron enters circulation via LSC
Causes of gallstone formation
Too much water absorption from bile
Too much bile acid absorption from bile
Too much cholesterol in bile
Epithelial inflammation
