The hepatic artery carries blood from the aorta and supplies oxygenated blood to the liver, pancreas and duodenum. The main function of the left and the right hepatic artery is to supply blood (oxygen and nutrients) to the liver.
The portal vein is not a true vein as it does not supply blood directly into the heart. The main function of the hepatic portal vein is to supply metabolic substrates to the liver. The portal venous blood brings the nutrients absorbed by the mucosa of the small intestine to the liver.