13._Liver_study_guide

Function of the Hepatobiliary System

I. Structure of the Liver

• Blood Supply

  • Hepatic artery: supplies oxygenated blood to the liver.

  • Portal vein: carries blood rich in nutrients from the gastrointestinal tract.

  • Hepatic vein: drains deoxygenated blood from the liver into the inferior vena cava.

II. Functional Unit of the Liver: The Hepatic Lobule

• Components of the Hepatic Lobule

  1. Hepatocytes:

     • Functional cells of the liver arranged in double rows radiating from a central vein.

  2. Sinusoids:

     • Specialized capillaries surrounding hepatocytes, receive blood from hepatic artery and portal vein, leading to central vein.

     • Kupffer cells:

       • Phagocytes lining sinusoids that filter bacteria and foreign substances from portal circulation.

  3. Bile Canaliculi:

     • Ducts found between rows of hepatocytes, receive bile produced by hepatocytes, eventually emptying into the hepatic duct.

III. Hepatobiliary Tree

• Components

  • Hepatic duct: joins with the cystic duct to form the common bile duct.

  • Common bile duct: joins with the pancreatic duct at the ampulla of Vater, emptying into the duodenum through the sphincter of Oddi, regulating the flow into the duodenum.

Normal Physiology of the Hepatobiliary System

• Functions of the Liver:

  • Bile Synthesis:

    • Bile salts for fat digestion/absorption.

    • Bilirubin is a pigment formed from the destruction of RBCs; converted from free/unconjugated to water-soluble conjugated form for excretion in bile.

  • Metabolism of Nutrients:

    • Carbohydrates (CHO):

      • Stabilizes blood glucose by storing/releasing glucose from glycogen, converts CHO to fat, creates glucose from amino acids (gluconeogenesis).

    • Proteins:

      • Decomposes proteins into amino acids for the synthesis of new proteins, converts ammonia to urea for urine excretion.

    • Fats:

      • Breaks down triglycerides for ATP production, synthesizes lipoproteins, phospholipids, and cholesterol.

  • Vitamin and Mineral Metabolism:

    • Storage and release of vitamins/minerals, assists in fat-soluble vitamins absorption, activates vitamin D.

  • Drug and Hormone Metabolism:

    • Uses enzyme systems in hepatocytes to detoxify chemicals, making them water-soluble for excretion (ex: cytochrome P450 system).

  • Phagocytosis:

    • Destroys bacteria and foreign particles absorbed from the GI tract.

  • Storage of Blood:

    • Blood can be redirected into circulation during hypovolemia or shock.

Pathological Changes & Nursing Considerations

• Common Pathological Changes

  • Inflammation of the liver leading to complications.

• Predisposing Factors (PF):

  • Exposure to toxics/drugs.

  • Hepatoviruses:

    • HAV: Contaminated food, poor hygiene.

    • HBV: IV drug abuse, healthcare workers, high-risk sexual behaviors.

    • HCV: IV drug abuse, blood products.

    • HDV: Requires HBV infection.

    • HEV: Mainly in developing countries.

• Nursing Problems:

  • Example of disorder: Viral Hepatitis

    • Hepatitis A: Fecal-oral route transmission, no chronic state.

    • Hepatitis B: Blood/body secretions, chronic state possible.

    • Hepatitis C: Blood transmission, chronic state.

    • Hepatitis D: Blood transmission, chronic state.

    • Hepatitis E: Fecal-oral route, no chronic state.

Assessment Findings and Phase Breakdown

• Incubation Period and symptom phases:

  • Preicteric/Prodromal Phase: General malaise, fatigue.

  • Icteric Phase: Jaundice; increase in bilirubin levels.

  • Convalescent Phase: Recovery, resolution of symptoms.

Common Liver Function Tests

A. Indications of Liver Inflammation/Injury

1. Increase in:

   • ALT (Alanine Aminotransferase): Enzyme specific to the liver.

   • AST (Aspartate Aminotransferase): Found in other organs too, but elevated indicates liver injury.

B. Indications of Impaired Protein Synthesis

1. Decrease in:

   • Serum protein/Albumin levels.

   • Prolonged Prothrombin time (increased).

C. Indications of Impaired Excretory Function

1. Increase in:

   • Bilirubin levels: Indicates problems with bile excretion.

   • Alkaline Phosphatase (ALP): Elevated in case of obstructed bile flow.