Hepatobiliary 1 Flashcards
Where is the liver located and what surrounds it?
Upper right abdominal quadrant; tough fibroelastic capsule
Functional unit of the liver is the:
lobule (all hepatocytes that drain into single central branch of the hepatic vein)
What is at the center of each lobule? The corner?
Center = Hepatic vein
Corner = Triad (bile duct, hepatic artery, portal vein)
Hepatocytes form an epithelium that separates 2 fluid spaces; one is for __________ and the other one called the ___________ which receives blood from what structures?
bile
sinusoid; hepatic artery and portal vein
What do microvilli on BOTH sides of hepatocytes do?
Increase SA
Where are Kuppfer cells found and what do they do?
found in sinusoid, macrophages that consume RBC’s, bacteria, etc.
Where are the endothelial cells found and what do they do?
found in sinusoid; form porous structure that allows plasma and solutes to move through freely
Where are stellate cells found and what do they do?
in the perisinusoidal space; fat-storing cells involved in storage of vitamin A.
They can transform into myofibroblasts and help regenerate liver
Function of hepatocytes differ, it all depends on:
Oxygen supply
Which hepatocytes are highly oxygenated and involved in amino acid metabolism, gluconeogenesis, ureagenesis, cholesterol synthesis, and bile formation?
Cells in Zone I (farthest from central vein)
Which hepatocytes get the least amount of oxygen and are involved in glycolysis, glycogen synthesis, lipogenesis, ketogenesis, and drug metabolism?
Cells in Zone III (closest to central vein)
The valveless hepatic portal vein drains the stomach, splee, pancreas, and small/large intestine and supplies the liver with how much of its OWN oxygen need?
60-70% (even though venous!) with fast flow
What does the hepatic vein do?
Carries venous outflow from liver to inferior vena cava
Liver can do biotransformation via phase I and phase II reactions? What is biotransformation and what are the phases?
Biotransformation is: substances taken from blood are either returned to circulation or excreted in bile
Phase 1: oxidation-reduction using CYP450
Phase 2: makes metabolites more polar/water soluble in blood or bile for excretion
What are the four major functions of the liver?
- ) biotransformation
- ) filtration
- ) hormone conversion and activation
- ) nutrient metabolism
What cells perform filtration within the kidney?
Kuppfer cells
What two hormones does the liver deal with?
- hydroxylation of vitamin D (initial site)
- deiondination of T4 into T3
Carb metabolism:
- ) Liver stores glucose as glycogen which it can breakdown to maintain blood sugar (7-20% weight)
- ) during fasting the liver can use gluconeogenesis to synthesize glucose from AA and lactic acid
- ) converts carbs into triglycerides for storage in adipose
Lipid metabolism:
1.) fat is split into glycerol and fatty acids
Almost all synthesis of fats from carbs and protein occurs in the liver. This fat can be transported as triglycerides in lipoproteins to be stored in:
Adipose tissue
What does fatty acids oxidize into and what happens to it?
Acetyl-CoA;
- can enter krebs cycle to generate ATP
- synthesize cholesterol
- converted to keynotes during glucose deficiency
Dietary cholesterol is packaged into _________ which can travel to adipose tissue or muscle
chylomicrons
The liver can synthesize cholesterol “de novo”, this means:
Does not need a direct precursor to synthesize
Liver takes up cholesterol in the form of LDL and can export it in 2 forms to:
- Synthesize bile acids directly
- Enter the blood in the form of VLDL to be transported to other cells for manufacture of cellular components (steroid hormones)
Protein metabolism produces circulating plasma proteins like albumin, which:
Maintains plasma oncotic pressure and binds/transports substances in blood like hormones, drugs, etc.
Transamination:
Transfer of AA group to an acceptor (ketoacid), which allows the AA to participate in gluconeogenesis or lipid synthesis
Deamination:
conversion of AA to ketoacids and ammonia
Ammonia is a byproduct of deamination, what does it convert to and what happens?
Urea, excreted by the kidneys or some diffused into intestines
Some of the ammonia that enters the intestines (either from unabsorbed protein or bacterial deamination) is absorbed into portal circulation then converted to urea in liver. What happens with severe liver disease?
Urea synthesis is impaired and ammonia can accumulate into blood
What is bilirubin?
A pigment that gives bile its color, product of RBC breakdown
List the steps of how hemoglobin becomes conjugated bilirubin:
- ) hemoglobin is broken down into biliverdin
- ) this rapidly converts to free bilirubin which binds to albumin in the blood (still “free”)
- ) When it gets to the liver, it is converted into conjugated bilirubin and glucuronic acid is added to it
- ) exported into bile where it is now soluble!
Bilirubin can be converted into uribilinogen by intestinal flora. What can urobilinogen do?
- ) excreted in feces
2. ) return to liver via portal circulation to be re-excreted into bile (small amount to kidneys)
Free bilirubin is also called (direct/indirect)
indirect
Conjugated bilirubin is also called (direct/indirect)
direct
What causes jaundice?
Elevated plasma bilirubin conc. (>1.5-3mg/dl)
- excessive RBC lysis
- decreased hepatic flow
- limited conjugation of bilirubin
- obstruction of canaliculi or bile ducts
What does bile allow that the kidney cannot do?
Excretion of bilirubin, cholesterol, and other substances not excreted by the kidneys
What is bile made up of?
Bile salts, bile acids, bilirubin, cholesterol, and lecithin
Bile acids and bile salts promote digestion and absorption of lipids from intestines, how do they do this?
Aid in formation of micelles which emulsify lipids to be absorbed
Which are neutral and not very water soluble: (bile acids or bile salts)?
Bile acids (they are de-protonated from bile salts in the duodenum and absorbed PASSIVELY)
Which is more concentrated: (hepatic bile/gallbladder bile)?
Gallbladder bile (water is removed)
Many bile acids are reabsorbed in the GI tract and brought where?
the liver (can recirculate 5 times during meal)
The ALT and AST are liver function tests that increase in proportion with:
Breakdown of hepatocytes (liver damage)
Serum albumin (PTT) tells us the livers ability to:
make necessary proteins (limits of blood flow?)
Alkaline phosphatase measures:
hepatic excretory function
