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95 Cards in this Set
- Front
- Back
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Liver is made of ___ segments.
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8
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Liver segments ____ make up the left lobe while ____ make up the right lobe. They are divided in a (clockwise, counterclockwise) fashion.
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2-4; 5-8
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What is liver segment 1?
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The caudate lobe.
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What's special about the caudate lobe?
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It drains via the hepatic vein but can also drain directly into the IVC.
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What is the liver's blood supply coming IN?
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Dual blood supply.
About 2/3 comes from portal vein; The other 1/3 comes from the hepatic artery. |
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What supplies nutrients and oxygen to the liver?
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The portal veins supplies nutrients because it directly drains the intestines (oxygen poor). The hepatic artery supplies oxygen, but is nutrient poor.
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What is the liver sinusoid?
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A liver sinusoid is a type of sinusoidal blood vessel (with fenestrated, discontinuous endothelium) that serves as a location for the oxygen-rich blood from the hepatic artery and the nutrient-rich blood from the portal vein.
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Sinusoids can be divided into zones with zone ___ in the periportal region and zone ___ in the central vein region.
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1;3
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The blood travels in the direction of zone __ (from portal vein/hepatic artery) to zone ___ (towards the central vein, eventually out of the hepatic vein)
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1; 3
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sinusoids have ____ that allows nutrients to enter hepatocytes.
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Fenestrated epithelium
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What is the Space of Disse?
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The space between the endothelium of fenestrated sinusoids and the hepatocytes.
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Which of zone 1 or 3 is more:
1) Oxygen rich 2) Nutrient rich 3) High metabolic rate 4) Primarily functions in lipid synthesis |
1) Zone 1
2) Zone 1 3) Zone 1 4) Zone 3 |
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What can happen in the space of Disse if there is stress?
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The stellate cells which normally store vitamin A can become fibroblasts and secrete collagen, thus inducing fibrosis and causing portal hypertension.
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Major protein made by liver
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albumin
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Albumin 1/2 life
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21 days. Good indicator of overall nutrition status
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What makes coagulation factors (except factor VIII)?
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the liver
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The is the most sensitive test of liver function?
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prothrombin time, as greater than 90% of the liver must be damaged for it to be prolonged.
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Lipophilic compounds are carried in the circulation bound to _____
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albumin
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Once lipophilic compounds bound to albumin get into the hepatocyte, what happens?
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Enzymes in the smooth ER convert lipophilic compounds to hydrophilic molecules.
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What are the phases of biotransformation?
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Phase 1 activation
Phase 2 conjugation |
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What happens in Phase 1?
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There is a hydrophilic "handle" (usually -OH) added to the molecule for subsequent conjugation.
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What enzyme class performs Phase 1 activation?
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Cytochrome P450s
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What happens in Phase 2?
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Something is added onto the lipophilic molecule (may or may not be activated via Phase 1 reaction) to make it excretable in bile or urine.
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What happens in the metabolism of acetaminophen?
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1) Majority gets metabolized via conjugation (phase 2) and is excreted via the bile and urine.
2) Some gets metabolized via CYP2E1 to a metabolite (NAPQI) that is toxic to liver cells. 3) Normally the phase 1 product is quickly conjugated with glutathione to a nontoxic metabolite that can be eliminated |
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T/F Phase 2 conjugation is preserved in advanced liver disease
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T
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Bile acids are made from _________
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cholesterol
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What serves as a way to eliminate bilirubin from the liver?
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Bile acids
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yellow breakdown product of normal heme catabolism.
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bilirubin
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What is unconjugated bilirubin?
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Heme is released from breakdown of RBCs. The heme is then turned into unconjugated bilirubin in the reticuloendothelial cells of the spleen. This unconjugated bilirubin is not soluble in water, due to intramolecular hydrogen bonding. It is then bound to albumin and sent to the liver.
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Unconjugated bilirubin is aka ______ while conjugated is _______
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indirect; direct
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What is the conjugated bilirubin conjugated with?
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glucuronic acid
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What conjugates the bilirubin with glucuronic acid? Where?
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Glucuronyltransferase, in the liver
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What does the conjugation of bilirubin due to the molecule?
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Makes it water soluble
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______________ bilirubin is water -insoluble and is attached to albumin to get carried to the liver
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Unconjugated.
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Most sensitive liver function test, dept on liver's ability to make clotting factors
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PT/INR (Prothrombin time)
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What is urobilinogen? How is it made?
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It is formed in the intestines by bacteria. Then some is reabsorbed back into the blood and excreted into the urine.
It's responsible for the yellow color of urine. |
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What does the presence of urobilinogen in the urine in jaundice mean?
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It means there is an incomplete block of the bile ducts, because SOME of the bile is getting into the intestine because the bacteria in the intestine for urobilinogen.
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What is stercobilinogen?
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In the intestine, bilirubin is converted by bacteria to stercobilinogen. Stercobilinogen is absorbed and excreted by either the liver or the kidney. Stercobilinogen is oxidized to stercobilin, which is responsible for the pigmentation of feces.
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What is delta bilirubin?
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Conjugated bilirubin bound to albumin (usually we only think of unconjugated bilirubin as bound to albumin)
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What are 3 abnormalities that can happen with unconjugated bilirubin?
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Over production (hemolysis)
Displacement from albumin (drugs) Conjugation by UDP transferase |
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What is Gilbert's syndrome?
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Reduced activity of glucuronyltransferase (conjugates bilirubin to glucuronic acid to make it soluble).
As a result there is an increase in unconjugated/indirect bilirubin, causing jaundice. |
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most common hereditary cause of jaundice (5-10% of population)
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Gilbert's syndrome
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What is Crigler-Najjar syndrome Type 1?
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Complete absence of glucuronyltransferase causing severe jaundice.
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What is Crigler-Najjar syndrome, type II?
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partial deficiency of glucuronyltransferase
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What are 3 abnormalities in conjugated Bilirubin Metabolism?
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1) Problems with secretion into the canaliculus (rate limiting step)
2) Obstruction of bile flow 3) Hereditary d/os, such as Dubin Johnson Syndrome and Rubin Syndrome |
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What is the rate-limiting step of bilirubin transformation and metabolism?
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secretion into the canaliculus
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What type of bilirubin will be increased (and thus cause jaundice) in excess hemolysis?
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Unconjugated
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What type of bilirubin will be increased (and thus cause jaundice) in Gilbert's syndrome?
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unconjugated
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What type of bilirubin will be increased (and thus cause jaundice) in hepatitis/cirrhosis?
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conjugated, urobilinogen
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What type of bilirubin will be increased (and thus cause jaundice) in Gallstones/tumors blocking biliary tract?
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conjugated, urobilinogen
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Most common form of jaundice is due to an increased in _______ bilirubin.
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Conjugated
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why is albumin a poor choice for a liver function marker?
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Long half life, also dependent on nutritional factors
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What other things might cause an elongated PT than liver injury?
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Vitamin K deficiency. must make sure patient doesn't have this.
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What are two markers for hepatocellular (not cholestatic) inflammation?
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AST, ALT
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Where is AST primarily located?
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Primarily in mitochondria. Not liver-specific.
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Where is ALT primarily located?
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Primarily cytosol. Liver-specific.
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Which of ALT or AST is more important marker of liver dysfunction?
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ALT
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Where is Alkaline phosphatase located?
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Bile duct epithelium
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If there is a cholestatic injury (eg., inflammation from stone), which liver enzymes will be elevated?
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Alkaline phosphatase more than ALT/AST
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What is the timing of acute vs subacute vs chronic liver injury?
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Acute: <6 months
Subacute: 3-6 months Chronic: >6 months |
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What are the 4 essential functions of hepatocytes?
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1) Intermediary metabolism
2) Protein synthesis 3) Solubilization of lipophilic compounds (biotransformation) 4) Excretion of bile |
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4 Functional Compartments of the Liver
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Vascular System
Sinusoidal Lining Cells Hepatic Parenchyma Biliary (Excretory) System |
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What are the sinusoids?
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Terminal branches of the portal vein and hepatic artery that anastomose form the sinusoids.
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Special features of sinusoids
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Very porous, allowing everything but formed elements of blood to pass from lumen of sinusoid into Space of Disse
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The sinusoids empty into the _____ veins which drain into ____ veins and then to IVC.
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Central; Hepatic
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What is the Kupffer cell?
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specialized macrophages located in the liver lining the walls of the sinusoids that form part of the reticuloendothelial system (RES) (also called mononuclear phagocyte system).
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Shunts between the portal and systemic vascular systems become functional in cirrhosis due to high sinusoidal pressure causing resistance to flow. What are the 2 types of shunts?
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1) Intrahepatic: between branches of hepatic artery and portal venous systems
2) Extrahepatic: between esophageal venous system and portal venous system |
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What are esophageal varices?
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Extrahepatic shunts between the esophageal (systemic) venous system and portal venous system. They can hemorrhage and be fatal.
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Increased pressure in the hepatic sinusoids, such as seen in cirrhosis and venous outflow obstruction, may contribute to the formation of _______
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ascites.
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ascities: defn
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accumulation of fluid in the peritoneal cavity
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What do the Kupffer cells do?
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Phagocytic functions, including metabolism of bilirubin, killing microbes, storing iron, storage of products of inborn errors of metabolism, digestion of effete hepatocytes.
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Cells that line sinusoids and normally involved in vitamin A metabolism.
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Stellate cells
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What is the classic hepatic lobule?
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Anatomically defined unit of hepatic parenchyma.
The apices contain the portal tracts (with hepatic arteriole, portal venule, and bile ductule). These anastomose to form sinusoids that transport blood from the portal tracts to veins in the center of the lobule. (central veins) |
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Anoxia or congestion most severely damages what zone?
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The zone around the central vein. This is because the oxygen-rich hepatic a. supply is furthest from it.
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What is Rappaport's acinus?
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That portion of hepatic parenchyma which receives its blood supply from one terminal portal venule and its accompanying hepatic arteriole.
Aka the microcirculatory unit of liver. |
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Which hepatocytes are most vulnerable to anoxia or toxic injury and why?
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Those in zone 3, further away from the oxygenated blood.
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(Centrilobular, Periportal) hepatocytes are less vulnerable to toxic and ischemic injury.
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Periportal
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How is bile excreted?
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It's excreted into the canaliculus, a small canal formed by plasma membranes of two adjacent hepatocytes.
It flows thru the canaliculus into the intrahepatic ducts and then into the extrahepatic biliary system. |
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Impaired excreted of bile
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cholestasis
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Clinical manifestation of most cholestatic disorders
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jaundice (increased [bilirubin] in blood and lymph)
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advantages of using ultrasound to evaluate liver
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1) no ionizing radiation
2) no need for IV contrast material 3) liver is ideally positioned anatomically for ultrasound eval. |
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T/F Ultrasound usefulness is highly dependent on skill and experience of operator of the US equipment.
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T
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Radionuclide Scan: What happens in liver evaluation?
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Radionuclide agent is injected IV.
Liver takes up the agent. Liver slowly excretes the agent through the biliary tree. This process can be visualized to see if there's any areas of abnormalities. |
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Normal appearance of liver via ultrasound
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Homogenous array of fine echoes.
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Anechoic: defn
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cystic structures that contain fluid and produce no echoes.
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How do cysts appear on ultrasound.
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Well circumscribed, anechoic areas
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How does diffuse liver disease appear on ultrasound?
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Increase in general echogenic pattern of liver. Heterogeneity.
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What is the best way to assess acute cholecystitis?
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Evaluation of the gallbladder with ultrasound
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How do gallstones look on ultrasound?
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Highly echogenic foci that move freely within the gallbladder and cause an acoustic shadow
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What are advantages of CT?
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High resolution images
Rapid evaluation Characterize focal lesions Cyst, hemangioma, tumor More detailed information about lesions c/w US Characterize diffuse liver disease –associated findings |
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What are potential problems with the iodinated contrast used in CT imaging of liver?
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can cause allergic rxns.
contraindicated in renal insufficiency. |
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What are advantages of MRI?
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Image in any plane with equal resolution
No ionizing radiation No iodinated IV contrast Gadolinium – rare allergic reactions, does not damage kidneys Even better characterization of focal lesions Evolving techniques |
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What are disadvantages of MRI?
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expensive, not as readily available, requires longer time period (not good for emergency)
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represents a non invasive way to see the intra and extrahepatic bile ducts through MR
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MR Cholangiopancreatography
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What is percutanous transhepatic cholangiography? (PTC)
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Injection of iodinate contrast materal. bile ducts are usually seen quickly if they're enlarged
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