The liver receives the oxygen and nutrients it needs in blood that comes from two large blood vessels:
Portal vein
Hepatic artery
The portal vein provides about two thirds of the blood. This blood contains oxygen and many nutrients brought to the liver from the intestines for processing. The hepatic artery provides the remaining one third of blood. This oxygen-rich blood comes from the heart and provides the liver with about half of its oxygen supply. Receiving blood from two blood vessels helps protect the liver: If one of these blood vessels is damaged, the liver can often continue to function because it receives oxygen and nutrients from the other blood supply.
Blood Supply of the Liver
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Blood leaves the liver through the hepatic veins. This blood is a mixture of blood from the hepatic artery and from the portal vein. The hepatic veins carry blood to the inferior vena cava—the largest vein in the body—which then carries blood from the abdomen and lower parts of the body to the right side of the heart.
Blood vessel (vascular) disorders of the liver usually result from inadequate blood flow—whether into or out of the liver. If the problem is blood flow out of the liver, blood backs up in the liver, causing congestion which can result in an enlarged liver Congestive Hepatopathy Congestive hepatopathy is a backup of blood in the liver, resulting from heart failure. (See also Overview of Blood Vessel Disorders of the Liver.) Severe heart failure causes blood to back... read more . In either case, liver cells do not receive enough blood (called ischemia) and thus are deprived of oxygen and nutrients. In ischemic cholangiopathy Ischemic Cholangiopathy Ischemic cholangiopathy is damage to one or more bile ducts caused by inadequate blood flow. (See also Overview of Blood Vessel Disorders of the Liver.) Bile ducts (such as the hepatic ducts... read more , it is the bile ducts that do not receive enough blood.
Inadequate blood flow—into or out of the liver—may result from heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more 
or disorders that make blood more likely to clot (clotting disorders). In clotting disorders, a clot may block the portal vein or a hepatic vein, slowing or blocking blood flow. Disorders with blockages in blood flow include
Budd-Chiari syndrome Budd-Chiari Syndrome Budd-Chiari syndrome is caused by blood clots that completely or partially block blood flow from the liver. The blockage may occur anywhere from the small and large veins that carry blood from... read more , which results when blood clots block blood flow from the liver
Portal vein thrombosis Portal Vein Thrombosis Portal vein thrombosis is blockage or narrowing of the portal vein (the blood vessel that brings blood to the liver from the intestines) by a blood clot. Most people have no symptoms, but in... read more , which is a blockage or narrowing of the portal vein (the blood vessel that brings blood to the liver from the intestines) by a blood clot
Sinusoidal obstruction syndrome Sinusoidal Obstruction Syndrome of the Liver Sinusoidal obstruction syndrome of the liver is blockage of the very small (microscopic) veins in the liver. Fluid tends to accumulate in the abdomen, the spleen may enlarge, and severe bleeding... read more (previously called veno-occlusive disease), which arises when very small blood vessels within the liver are blocked
