L35: Hepatic physiology Flashcards
what organ has the greatest regenerative capacity
liver; it is able to regenerate
what are the 2 blood sources of the liver
- hepatic artery from the aorta (provides O2)
- hepatic portal vein from the GI tract (provides nutrients)
where does the hepatic portal vein collect blood from
stomach, SI and part of LI
takes nutrients and delivers it to the liver
most of the liver blood is ____ blood
venous
increases after a meal
through what vein does blood leave the liver
heaptic vein
what are the functional units of the liver
lobules = hexagonal tissue surrounding a central vein
what is the role of Kupffer cells
destroy old RBCs and bacteria
get exposed to large volumes of blood
Vitamin A is stored as ____ in ?
retinol
hepatocytes or stellate cells
what is the space of disse
space b/w hepatocytes and sinusoids
fills w/ collagen = fibrosis
what is the portal triad
the 3 vessels in a lobule that drain into a central vein
- bile duct
- hepatic artery
- portal vein
blood enters the sinusoids from the _____ vein and the ____ artery
portal vein and hepatic artery
what are the different zones in the lobule
periportal hepatocytes (zone I)
centrilobular (pericentral, zone II)
hepatocytes (zone III)
what is responsible for the variability in activity of each zone of the lobule
heterogeneity of O2 supply
what zone of the lobule is highest in O2
zone I
* has many mitochondria
* oxidative metabolism
* bile acid secretion
* glycogen and other nutrient storage
what lobule zone is responsible for bile acid secretion
zone I
what lobule zone is concerned w/ oxidative metabolism (FA oxidation, gluconeogenesis, urea genesis)
zone I
what zone is the transition zone
zone II
What lobule zone is lowest in O2 and therefore anaerobic metabolism occurs here
zone II
in what zone of the lobule does biotransformation of drugs/chemicals/toxins occur
zone III
what zone is most sensitive to damage caused by ischemia
zone III - least O2 supply
most susceptible to centrilobular necrosis, hypoxia, congestion
what is centrilobular necrosis and what zone does it usually occur
necrosis around the central vein
zone III
what are the 2 capillary beds blood runs through before it returns to the heart
- mesenteric
- portal
what drives blood through the portal capillary bed
- pressure in portal vein being higher than in the hepatic sinusoids (precapillary resistance in portal inflow is low)
- central vein of liver is large so resistance is low
- venous outflow of the liver goes into thoracic vena cava
what is the consequence of right sided heart failure on the liver?
it increases vena cava pressure which leads to reduced blood flow from the intestine
excess interstitial fluid leaks into edematous tossie and accumulates in the peritoneal cavity (ascites)
what can cause necrosis of zone 1 (periportal)
- phosphorous poisoning (rat poison, fertilizer, fireworks)
- eclampsia (sudden pregnancy/postpartum seizures)
what can cause necrosis of zone 3 (centrilobular zone)
- ischemic injury
- toxic effects
- carbon tetrachloride exposure
- chloroform ingestion
what liver enzymes are most likely elevated when there is an increase in cell membrane permeability or death
- alanine transaminase (ALT)
- asparate transaminase (AST)
- alkaline phosphatase (ALP)
- gamma glutamyl transpeptidase (GGT)
elevated liver enzymes may indicate?
inflammed or damaged liver cells b/c they leak higher than normal amounts of enzymes into the bloodstream which can result in elevated liver enzymes in a blood test
why does a decreased uptake and conversion of ammonia into urea cause high ammonia concentrations
high ammonia concentration in urine are followed by low urea nitrogen concentration and PU/PD
b/c urine concentrating ability depends on medullary interstitial tonicity which is generated by urea and NaCl
what is the function of bile
- excretory route for solutes that aren’t excreted by the kidney
- bile salts and acids are needed for lipid digestion and absorption
what is the composition of bile
- bile salts (50%)
- phospholipids (40%)
- bilirubin, electrolytes, water
bile is continuously secreted by ____ into _____
hepatocytes into canaliculi
where are bile caniculi located
b/w adjacent hepatocytes, they drain into bile ducts at the periphery of lobules
what are the 2 primary bile acids
- cholic acid
- chenodeoxycholic acid
what does the liver conjugate bile acids w/
Taurine and glycine
what are the 2 secondary bile acids and how are they formed
deoxycholic and lithocholic acid
primary bile acids that get dehydroxylated by bacteria into secondary bile acids
bile salts are derivates of ?
cholesterol
what happens to bile salts after they are used in fat digestion and absorption
they get reabsorbed into the blood through an active transport mechanism in the distal ileum and by passive absorption throughout the intestine
what are the sites at which bile salts get reabsorbed
- distal ileum (via active transport)
- throughout the intestines (passive abs)
after being reabsorbed how do bile salts get back to the liver
hepatic portal system
= enterophepatic circulation
is bilirubin involved in digestion
no but excreted in bile
