Chapter 31_1 flashcards
(16 cards)
Liver: Major Functions
Digestion (bile production), Metabolism (fats, proteins, carbs), Bilirubin conjugation, Detoxification, Storage (vitamins, iron), Synthesis (albumin, coagulation factors).
Dual Blood Supply of the Liver
The liver receives blood from two sources: the Hepatic Artery (provides 25% of blood flow, oxygen-rich) and the Portal Vein (provides 75% of blood flow, drains GI tract, nutrient-rich).
Portal Vein: Significance
Drains all venous blood from the GI system (intestine, spleen, pancreas, stomach) and brings it to the liver for detoxification and processing before it enters the main circulation.
Key Liver Cells: Hepatocytes & Kupffer Cells
Hepatocytes are the functional cells of the liver, capable of regeneration, which perform most of the liver’s metabolic tasks. Kupffer cells are macrophages that line the liver’s sinusoids and detoxify the blood by phagocytosing foreign matter and old RBCs.
Bilirubin Metabolism: Basic Process
Aged RBCs break down into heme, which becomes unconjugated bilirubin (not water-soluble). The liver performs conjugation to make bilirubin water-soluble so it can be excreted in bile.
Jaundice (Icterus): Definition & Cause
The yellowing of the skin and sclera caused by hyperbilirubinemia (a high amount of bilirubin in the bloodstream).
Three Types of Jaundice: Prehepatic, Intrahepatic, Posthepatic
Prehepatic: Caused by excessive RBC hemolysis (e.g., in newborns), overwhelming the liver’s ability to conjugate bilirubin. Intrahepatic: Caused by hepatocellular injury, where the liver itself cannot conjugate bilirubin properly (e.g., hepatitis). Posthepatic: Caused by bile duct obstruction, which prevents already-conjugated bilirubin from being excreted.
Portal Hypertension: Definition & Cause
Abnormally high pressure within the portal vein, most often caused by cirrhosis of the liver, where fibrotic tissue creates resistance to blood flow.
Portal Hypertension: Major Complications
Causes backup of venous pressure, leading to: Esophageal varices, Caput medusa (distended abdominal veins), Splenomegaly (enlarged spleen), Ascites (fluid in the abdomen), and Hemorrhoids.
Esophageal Varices: Pathophysiology
Portal hypertension causes blood to back up and form dilated, fragile veins in the lower esophagus. These are prone to rupture, causing life-threatening hematemesis (vomiting of blood).
Hepatic Encephalopathy: Pathophysiology & Key Sign
An alteration of mental status due to liver failure. The failing liver cannot detoxify the blood, leading to an accumulation of nitrogenous wastes like ammonia (NH3) that are toxic to the brain. A key sign is asterixis (a flapping tremor of the hands).
Cirrhosis: Definition & Pathophysiology
The final, irreversible stage of liver injury where the liver becomes scarred and fibrotic. Stellate cells, stimulated by chronic injury, produce excessive collagenous fibrous tissue that replaces functional hepatocytes.
Steatosis: Definition
Fatty liver; the accumulation of fat within hepatocytes. It is the initial cellular change in alcohol-related liver disease and the hallmark of NAFLD.
Assessment of Liver Disease: Common Symptoms
RUQ tenderness, jaundice, ascites (abdominal swelling), dark urine (from bilirubin), steatorrhea (light-colored, fatty stools from lack of bile), pruritus (itching from bile salts).
Diagnosis of Liver Disease: Key Lab Tests
Liver Function Tests (LFTs): ALT and AST (elevated in hepatocellular injury). Bilirubin (elevated). Albumin (decreased in chronic disease). Prothrombin Time (PT) (prolonged due to lack of coagulation factors).
Diagnosis of Liver Disease: Gold Standard
A liver biopsy is the gold standard for diagnosing the stage and severity of liver disease.
