Expansion
Zone 1 is periportal and best oxygenated; zone 3 is centrilobular and most vulnerable
Expansion
Blood flows from the portal triad at the corner of the lobule, through the sinusoids, to the central vein:
- Zone 1 (periportal) - closest to the triad, best oxygenated. Site of gluconeogenesis and oxidative metabolism. First affected by viral hepatitis and by ingested toxins
- Zone 2 - intermediate
- Zone 3 (centrilobular) - furthest from the supply, least oxygenated. Site of cytochrome P450 activity, glycolysis and lipogenesis. First affected by ischaemia and by drugs requiring metabolic activation
That last point explains two classic patterns. Paracetamol toxicity produces centrilobular (zone 3) necrosis, because P450 there converts it to the toxic metabolite NAPQI. And in cardiac failure, hepatic congestion produces centrilobular necrosis, giving the “nutmeg liver” appearance.
The portal triad itself contains a portal venule, a hepatic arteriole and a bile ductule, bile flowing in the opposite direction to blood.