Lecture 41 - Liver and Bile Acids Flashcards
what are the 3 main functions of the liver
- biotransformation
- storage
- synthesis
what are liver macrophages called
Kupffer cells
what are the additional functions of the liver
- bile production and secretion
- metabolism of protein, lipids, and carbs
- storage of glycogen, triglycerides, iron, copper, vitamins
- detoxification
- conversion of ammonia
- immune filter
- clotting factor production
T/F: the liver has a dual blood supply
TRUE
where does the liver receive blood from
- portal v. (75%)
- hepatic a. (25%)
describe the structure of the liver lobes
- hexagonal shape
- hepatocytes form cords radiating from central vein
- sinusoids lined with Kupffer cells
what composes the portal triad
- hepatic venule
- bile duct
- hepatic arteriole
what is the gall bladder
organ that stores bile
gallbladder contraction is stimulated by
CCK
T/F: horses don’t have gallbladders
TRUE
what is the limiting plate
ring of hepatocytes abutting the portal
Describe a classic hepatic lobule
based on blood flow
central vein and portal tracts at periphery
Describe portal lobules
based on bile flow; opposite to blood flow
organized as “triangle” with Portal tract at center
describe the route of bile through a portal lobule
- bile canaliculi
- canals
- bile ductules
- interlobular bile ducts
- intrahepatic ducts
- right/left ducts
- common hepatic duct
- common bile duct
- duodenum
what zones can the liver be divided into (name innermost to outermost)
- periportal (oxygenated blood)
- midzonal
- centrilobular (deoxygenated central v.)
hepatocytes in the periportal zone do what
- Cholesterol synthesis
- Fatty acid oxidation
- bile acid production
hepatocytes in the centrilobular zone do what
- glycolysis
- lipogenesis
- xenobiotic transformation
acinus
triangle-shaped unit containing a small portal tract (1) at the center and terminal hepatic venules (3) at the periphery
what amino acid is essential to cats
taurine
create a flowchart of the conversion of cholesterol to bile acid
cholesterol –[7a-hydroxylase]–> cholic acid –[taurine/glycine]–> taurocholic acid
T/F: bile acids are synthesized by Kuppfer cells
FALSE - hepatocytes
bile is an excretory route for what
fat-soluble metabolic waste (bilirubin, cholesterol, drugs, etc.)
T/F: the rate-limiting step of bile acid synthesis is 7a hydroxylation
TRUE
what drives bile acid transporation? what locations do they start and end in?
Bile Salt Export Pump (BSEP)
hepatocyte –> canalicular bile
the closure of ________ causes bile to back up into the cystic duct/gallbladder
sphincter of Oddi
what signals for secretion of bile acid in the duodenum
fat in duodenum and CCK
what is the significance of urodexycholic acid
hydrophilic synthetic bile acid administered to dogs/cats to increase the circulating bile acid “pool” to combat biliary disease
when returned to the liver, bile acid will be bound to
albumin
the entire bile acid pool recirculates ___ per meal
twice
bile salts escaping ileal reabsorption pass into the colon where they become
- deoxycholic acid
- lithocolic acid
Summarize the assimilation of fats in 6 steps
- pnacreas makes lipase delivered into lume of GI tract and hydrolyzes FA
- results in hydrophilic head and hydrophobic tail of TG
- Micelle forms
- micelle disassembles
- FA and BG are assembled into TG to make chylomicron
- chylomicron travels through intestinal lymphatics
T/F: milky white lymph and plasma lipemia is normal 1-2 hours after meals
TRUE
enterohepatic circulation
circulation of biliary acids, bilirubin, drugs or other substances from liver through the digestive tract and returning to the liver
Summarize bile salt recycling in enterhepatic circulation in 4 steps
- bile salts pass to ileum
- reabsorbed into circulation
- travel through hepatic protal v. to liver for recycling
- small amount of bile salts continue through GI tract and are eliminated
If liver function isimpaired, serum concentration of bile acid ____ after a meal
increases
what test is more sensitive to detecting bile-related disease
“challenge” test with pre- and post-prandial blood collection
cholecystokinin (CCK)
released in response to intraluminal fat
results in gallbladder contraction
secretin
released in response to intraluminal acid
results in bicarbonate secretion and neutralization of bile acids
what is the source of bilirubin
Breakdown of RBC hemoglobin
unconjugated bilirubin
bound to albumin; insoluble
conjugated bilirubin
unbound; soluble; passes through glomerulus
what converts heme to biliverdin
heme oidase
what converts biliverdin to bilirubin
biliverdin reductase
what enzyme makes bilirubin conjugated
uridine glucuronyl transferase
what makes feces brown
stercobilin
what are the 5 steps to bilirubin metabolism
- production
- hepatic uptake
- conjugation
- bile duct excretion
- intestinal delivery
causes of pre-hepatic icterus
- Rate of bilirubin production exceeds clearance
- RBCs are destroyed rapidly
causes of hepatic icterus
- liver function compromised so clearance cannot occur
- Acute and chronic liver conditions
causes of post-hepatic icterus
- Biliary system is unable to excrete via GI tract
- Biliary obstruction
