What are the approximate contributions of the portal vein and hepatic artery to the liver's blood supply, and how does this enable selective arterial delivery of chemotherapy?

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The liver has a dual blood supply: the portal vein carries about three quarters of the blood flow (nutrient-rich, lower oxygen), while the hepatic artery provides the remaining roughly one quarter (oxygen-rich). Normal liver tissue relies largely on portal venous inflow. Tumors, because of their abnormal blood vessel growth, tend to derive most of their blood from the hepatic artery. This difference allows selective arterial delivery of chemotherapy: by infusing the drug into the hepatic artery, you deliver high concentrations directly to the tumor via its main blood supply while the surrounding normal liver tissue—the part fed mainly by the portal vein—receives relatively less arterial perfusate and thus experiences less systemic exposure. This selective arterial approach underpins hepatic artery infusion and related therapies, aiming for maximum tumor exposure with minimized systemic toxicity.