Final answer:
The hepatic portal vein delivers the greatest amount of oxygenated flow to the liver by carrying partially deoxygenated blood that is still rich in oxygen, along with nutrients from the GI tract, surpassing even the oxygen-rich hepatic artery due to the volume of blood it transports.
Step-by-step explanation:
The vessel that provides the greatest amount of oxygenated blood flow to the liver is the hepatic portal vein (PV). While the hepatic artery supplies oxygen-rich blood to the liver, it is the hepatic portal vein that delivers not only nutrients absorbed from the gastrointestinal tract but also a significant amount of oxygen. This oxygen comes from the partially deoxygenated blood that still contains a substantial amount of oxygen. Hence, even though the hepatic artery carries oxygen-rich blood from the aorta, the hepatic portal vein is the major source of oxygen due to the larger volume of blood it carries to the liver. Other vessels mentioned, such as the Hepatic vein, Gastroduodenal Artery (GDA), and Superior Mesenteric Artery (SMA), do not provide the primary oxygenated blood to the liver as directly as the hepatic artery and hepatic portal vein do.