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Structural Units, Functional Models & Zonation, Zone 1 (Periportal),…

- - - - Drain local parenchyma lymph into major trunks
    - - Unmyelinated autonomic fibers (vascular tone & biliary secretion)
    - - Interlobular Bile Duct
      - Portal Venular branch
      - Hepatic Arteriolar branch
  - - - Sinusoidal (Basolateral) Pole
        
        Covered with abundant microvilli projecting into the Space of Disse to optimize exchange with blood plasma
      - Biliary (Apical) Pole
        
        Forms the wall of the bile canaliculi, sealed tightly by zonula occludens (tight junctions) to prevent bile leakage into sinusoids
      - Lateral Pole
        
        Contacts adjacent hepatocytes via desmosomes (structural support) and gap junctions (intercellular signal transduction)
    - - Kupffer Cells
        
        Resident phagocytic macrophages anchored inside sinusoids
      - Space of Disse (Perisinusoidal Space)
        
        Narrow interval between endothelial cells and hepatocyte microvilli housing Ito cells (Hepatic Stellate Cells), which store Vitamin A/lipids and synthesize reticulin fibers (and collagen in fibrosis)
      - Fenestrated Endothelium
        
        Discontinuous capillary lining without a continuous basal lamina, allowing plasma to flow freely into the perisinusoidal space
    - - Radiating cords of hepatocytes lined up between the portal triads and the central vein
- - - - Center: Central Vein
        
        Shape: Hexagon
  - - - Center: Portal Space
        
        Shape: Triangle
  - - - Center: Interlobular vascular axis
        
        Shape: Diamond / Rhomboid
- - - - Transitional / Adaptive during active digestive phases
        
        Lipogenesis
        
        CYP450 Detoxification
        
        Glycolysis
  - - - Intermediate
        
        Most vulnerable to Ischemia/Hypoxia, Alcoholic injury, & Acetaminophen toxicity
  - - - Intermediate
        
        Lowest Supply
  - - - Moderately susceptible
        
        Centrilobular Necrosis (first to undergo ischemic death)
  - - - Mid-way gradient
        
        Distal (Surrounds Central Vein)