Introduction to Liver Diseases Flashcards
What forms the parenchymal cells of the liver and how?
Endodermal foregut gives rise to liver bud (hepatic diverticulum) around 4 weeks.
Endoderm of diverticulum grows into the mesoderm-derived mesenchyme of the septum transversum
Endoderm forms the biliary tree as well as the parenchymal cells of the liver
What will the mesenchyme of the septum transversum become?
Forms the connective tissue of the liver -> fibroblasts and stellate cells, as well as Kupffer cells and **hematopoietic stem cells in fetal liver
What forms the endothelial cells of the liver sinusoids?
Remnants of the yolk sac circulation -> vitelline and umbilical vessels
What separates the right from the left lobe of the liver? What does it contain?
The falciform ligament
Contains the round ligament (ligamentum teres) -> remnant of umbilical vein, plays a role in caput medusae
How is the liver suspended off of the diaphragm?
Anterior and posterior coronary ligaments, which have sharp lateral transitions called the triangular ligaments
What visceral lobes are contained in the right anatomical lobe of the liver?
Right visceral lobe, caudate lobe (posterior), quadrate lobe (anterior)
What are the boundaries of the quadrate and caudate lobes?
Caudate - IVC laterally, porta hepatis anteriorly, ligamentum venosum medially
Quadrate - Gall bladder laterally, porta hepatis posteriorly, ligamentum teres medially
How does bile travel in the liver from hepatocytes to GI tract?
From hepatocytes -> bile canaliculi -> canals of Hering (intralobular bile ductules, lining sides) -> bile ducts in portal tracts -> hepatic ducts (from each lobe)-> common hepatic duct -> common bile duct (where it combines with cystic duct from gallbladder) -> duodenum, stopped by ampulla of Vater
What is a lobule vs an acinus as functional units of the liver?
Lobule - hexagon centered around central vein
Acinus - functional triangle with apex centered on central vein, and opposite side formed by hepatic vessels from the portal triad
What are the three zones of hepatocytes in the acinus?
Zone 1 - closest to incoming blood supply (periportal)
Zone 2 - intermediate
Zone 3 - nearest the central vein (centrilobular)
Which zone does the most oxidative metabolism, gluconeogenesis, transamination, protein, cholesterol, and urea synthesis? Why?
Zone 1 - closest to blood inflow, has highest oxygen content and numerous mitochondria
What are zone 3 hepatocytes important for? Where in the cell do these processes occur?
Have lower oxygen content, primarily function in biotransformation - phase 1 and phase 2 reactions
Phase 1 reactions - Smooth ER
Phase 2 - conjugation reactions occur in cytosol
What zone of hepatocytes are most susceptible to drugs / toxins / hypoxia / ischemia?
Hypoxia / Ischemia - zone 3, furthest from blood supply
Drugs / toxins - Zone 3 as well, due to phase 1 reactions (ethanol and acetaminophen toxicity causes centrilobular necrosis)
What zone is most susceptible to hemochromatosis?
Zone 1 - due to it seeing the most blood first -> takes up the most iron
What type of endothelial cells line the sinusoids? Why?
Fenestrated, discontinous endothelium lacking a basement membrane
-> allows for diffusion of materials into the space of Disse (btwn endothelial cells and hepatocytes)
What are stellate cells also called and what is their function?
Cells of Ito - function to store vitamin A, and are important in the pathogenesis of cirrhosis
What determines if the liver can be regenerated with normal anatomy following damage?
Loss or preservation of reticulin (Type III collagen) framework
What is the function of the Kupffer cells?
Phagocytic cells in sinusoids involved in clearance of exogenous (i.e. bacteria) and endogenous (i.e. immune complexes) substances
How does cholestasis cause hepatocellular damage?
Bile builds up -> pressure builds -> break through tight junctions on ductule cells -> bile leaks through and solubilizes cholesterol in cell membranes
-> damage to cell membranes
What is the hallmark of Hepatocellular injury (hepatitis syndromes) and what labs will be elevated? Which is more specific for liver?
Hepatocellular damage and necrosis, with associated inflammation depending on etiology
Labs elevated: ALT and AST
ALT is more specific for liver
Think ALT = AliverT
What is the hallmark of cholestatic disorders and what labs will be elevated? How do you confirm these elevated labs are from the liver?
Abnormalities in bile flow leads to liver damage, and increased conjugated bilirubin in blood
Alkaline phosphatase will be elevated, with gamma-glutamyl transferase (GGT) and 5’-nucleotidase as specific markers which can be ordered showing damage is from liver
What is cirrhosis?
The CHF of liver disease -> endstage of all diseases which can progress to chronic liver failure
Marked by diffuse fibrosis of liver associated with formation of abnormal nodules and vascular alterations
What is the definition of acute liver failure?
Loss of 80-90% of hepatic function within weeks, most commonly caused by fulminant hepatitis
What are the symptoms of acute liver failure and whhy?
Encephalopathy -> increased nitrogen wastes
Hypoglycemia -> decreased glucose homeostasis maintenance by liver
Coagulopathy -> decreased production of coagulation factors
Renal failure -> not well understood