Liver Histology

Overview

Introduction

• Blood supply to the liver    
  • liver receives majority of blood supply (75%) from the hepatic portal vein that carries venous blood that is largely depleted of oxygen
  • liver receives a lesser amount of blood supply (25%) from the hepatic artery, a branch of the celiac trunk, that carries oxygenated blood
  • in the liver, branches of the hepatic portal vein and hepatic artery supply sinusoids that bathe hepatocytes and provide for exchange of substances between the blood and liver cells
    • apical surfaces of hepatocytes face bile canaliculi
    • basolateral surfaces of hepatocytes face sinusoids
  • sinusoids empty into central veins, which empty into sublobular veins
    • sublobular veins converge to form larger hepatic veins 
    • blood leaves liver by the hepatic veins that empty into the inferior vena cava (IVC)
  • “irregular capillaries”
    • sinusoids are lined by Kupffer cells and fenestrated endothelial cells (pores 100-200 nm in diameter)
      • Kupffer cells are mononuclear phagocytic cells
    • no basement membrane between endothelium and underlying hepatocytes
    • these 2 structural modifications facilitates exchange of material in liver in perisinusoidal space (space of Disse)
      • space of Disse lies between basal surfaces of hepatocytes and basal surfaces of endothelial cells and Kupffer cells that line sinusoids
        • site of exchange of materials between blood and liver cells
• Liver acinus 
  • represents functional unit of hepatic parenchyma
  • hepatocytes in each liver acinus are described as being arranged in 3 concentric elliptical zones
    • zone I
      • periportal zone
      • cells in zone I are the first to receive oxygen, nutrients, and toxins from sinusoidal blood
      • cells are the first liver cells affected by viral hepatitis
    • zone II
      • intermediate zone
    • zone III
      • centrilobular zone
      • contains P450 system
      • cells are the first liver cells affected by ischemia and alcoholic hepatitis, and are most sensitive to toxic injury