The liver, an organ located in the upper right abdomen, plays a central role in health. It performs numerous functions, including processing nutrients, detoxifying harmful substances, and producing proteins. The liver’s ability to carry out these tasks relies heavily on its extensive blood supply. This anatomy ensures the liver receives resources and substances it must process.
Key Blood Vessels of the Liver
The liver receives blood from two primary sources, a dual blood supply. The first source is the hepatic artery, which delivers oxygenated blood to the liver. This arterial supply accounts for approximately 25% to 30% of liver blood flow. The hepatic artery provides oxygen for liver cell function.
The second and larger blood supply comes from the hepatic portal vein. This vessel carries deoxygenated blood rich in absorbed nutrients, medications, and toxins from the gastrointestinal tract, spleen, and pancreas. The hepatic portal vein contributes 70% to 75% of liver blood flow. This ensures absorbed substances are processed by the liver before entering general circulation.
Once blood has been processed by the liver, it exits through the hepatic veins. Typically, three large hepatic veins—the right, middle, and left—collect blood from various liver segments. These veins then drain into the inferior vena cava, a large vein carrying deoxygenated blood back to the heart.
The Liver’s Specialized Circulation
Blood entering the liver through the hepatic artery and hepatic portal vein does not mix in typical capillaries. Instead, these vessels branch into smaller arterioles and venules emptying into specialized vascular channels called hepatic sinusoids. These sinusoids are wider than capillaries and are lined with endothelial cells that have numerous pores or fenestrations. This discontinuous lining allows for close contact and efficient exchange of substances between the blood and liver cells (hepatocytes).
Within the sinusoids, oxygen-rich blood from the hepatic artery mixes with nutrient-rich, deoxygenated blood from the hepatic portal vein. This mixing ensures that hepatocytes receive oxygen and absorbed substances for metabolic activities. As blood flows through these sinusoids, it gradually moves towards the center of each liver lobule.
Within each lobule, the sinusoids converge into a central vein. Blood from these central veins then collects into progressively larger sublobular veins, merging to form the main hepatic veins. These veins carry processed blood out of the liver into the inferior vena cava, completing the circulatory pathway.
The Importance of Liver Blood Flow
The liver’s dual blood supply is important to its ability to perform its functions. The hepatic artery ensures a consistent supply of oxygenated blood, which is important for the liver’s active metabolic processes.
Meanwhile, the hepatic portal vein delivers nutrients and other absorbed compounds from the digestive system, allowing immediate processing. This direct route facilitates the liver’s role in nutrient metabolism, such as converting glucose into glycogen for storage and processing fats.
The structure of the hepatic sinusoids, with their fenestrated walls, enables extensive interaction between blood and hepatocytes. This contact is important for the liver’s detoxification capabilities, as it allows liver cells to efficiently filter and neutralize harmful substances (e.g., medications, environmental toxins), preventing them from reaching the rest of the body. The slow flow of blood through these wide sinusoids provides ample time for these biochemical reactions to occur. This specialized circulation also supports the liver’s production of bile (aids fat digestion) and various plasma proteins (e.g., blood clotting factors).