Zones
From a metabolic perspective, the functional unit is the hepatic acinus (terminal acinus), each of which is centered on the line connecting two portal triads and extends outwards to the two adjacent central veins. The periportal zone I is nearest to the entering vascular supply and receives the most oxygenated blood. Conversely, the centrilobular zone III has the poorest oxygenation and is relatively more sensitive to ischemic injury.
Functionally, zone I hepatocytes are specialized for oxidative liver functions such as gluconeogenesis, β-oxidation of fatty acids and cholesterol synthesis, while zone III cells are more important for glycolysis, lipogenesis and cytochrome P-450-based drug detoxification. This specialization is reflected histologically; the detoxifying zone III cells have the highest concentration of CYP2E1 and thus are most sensitive to NAPQI production in acetaminophen toxicity. Other zonal injury patterns include zone I deposition of hemosiderin in hemochromatosis and zone II necrosis in yellow fever.
Read more about this topic: Lobules Of Liver
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