Viral Hepatitis Flashcards
Explain the structure and function of the liver
The liver is made of many hexagon shaped structures called lobules. At the corner of each lobule is a collection of 3 vessels called the portal triad.
What 3 vessels make up the portal triad?
Portal vein, portal artery, and bile duct
What are hepatocytes?
The main cell type in the liver they remove unconjugated bilirubin through several conjugation reactions.
What are stellate cells?
They metabolize and store Vit A and produce connective tissue in the liver. They physically lie between endothelial cells and hepatocytes.
What are kupffer cells?
Macrophages that live in the sinusoids of hepatocytes. They destroy bacteria and remove debris from the blood. They also release inflammatory and fibrogenic cytokines and act as APCs.
Explain the 3 steps in the progression and development of cirrhosis
Stage 1: Steatosis: Build-up of lipids in hepatocytes that cause enlargement of the liver. Reversible
Stage 2: Steatonecrosis: Death of fatty hepatocytes and scarring. Kupffer cells are activated and release TNF-a and IL-1B that results in accumulation of connective tissue producing fibrotic scar. Reversible if caught early enough.
Stage 3: Cirrhosis. Irreversible loss of liver function.
Describe the basic morphology of a virus
The simplest viruses contain only genetic information and protein coat called capsid (non-enveloped virus)
Viruses have different shaped capsids (Helical, icosahedral or complex)
Viruses can be enveloped and/or have lipid membrane coating
May vary in size
List the 5 ways viruses are classified
Whether they contain DNA or RNA, Shape of the capsid, presence or absence of a lipid envelope, mode of replication, preferred cell type for replication (tropism)
What is tropism? What factors determine tropism?
Tropism describes a viruses ability to bind to particular host cell surface proteins determined by:
Expression of host receptors for the virus, presence of cellular transcription factors that recognize enhancer and promoter regions, anatomical barriers, local temperate, pH, host defences
List and describe the 3 mechanisms of cellular injury that occur as a result of viral infection
Direct cytopathic effects: Prevent synthesis of macromolecules, produce digestive enzymes and toxic proteins, or induce apoptosis
Antiviral immune response: Viral proteins presented on the surface of host cells so the immune system can recognize them. CD8 T cells accelerate liver failure by destroying infected hepatocytes.
Transformation of infected cells: Viruses can transform hepatocytes into malignant tumor cells which increases the expression of oncogenes or acting in an anti-apoptotic manner.
Infection with which Hepatitis viruses can lead to cirrhosis?
B and C
Explain the viral genome, viral family, route of transformation, average incubation period and diagnosis for Hepatitis A, B and C
Hepatitis A: ssRNA, hepatovirus family, spread by fecal-oral route (contaminated food or water), 2-4 week incubation period, diagnosis made by detection of serum IgM antibodies
Hepatitis B: dsDNA, hepadnavirus family, spread parenterally, sexually, and perinatally, incubation period 1-4 months, diagnosis made by detection of HBsAg or antibody to HBcAg
Hepatitis C: ssRNA, flaviridae family, spread parenterally and by sexual contact, incubation period 7-8 weeks, diagnosed based on PCR for HCV RNA and 3rd ten ELISA for antibody detection.
Fulminant hepatitis occurs most commonly in patients with which hepatitis infection?
HBV
What is acute asymptomatic infection with recovery?
Often identified by finding elevated liver enzymes and the presence of antiviral antibodies. Patient has no symptoms but may have markers of infection and then they recover.
What are the 4 phases of acute symptomatic hepatitis with recovery
Incubation period, symptomatic preicteric (pre-jaundice), Icterus (jaundice), and convalescence (time spent recovering from illness)
