Anatomy and Basic Functions of the Liver and Bilirubin Metabolism

The liver is the largest solid organ in the body and anatomically is divided into four lobes:• Right lobe: largest lobe• Left lobe• Quadrate lobe: lies between the gallbladder and round ligament of liver.• Caudate lobe: lies between the inferior vena cava (IVC), ligamentum venosum, and porta hepatis. Surgically the liver is divided into right and left halves. The quadrate and caudate anatomical lobes are often considered part of the left half, although some place a portion of the caudate lobe with the right lobe. Surgeons often divide the liver further into eight independent vascular segments based on its vasculature, with each segment receiving a major branch of the hepatic artery, portal vein, hepatic vein (drains the liver’s blood into the IVC), and biliary drainage. The external demarcation of the two liver halves runs in an imaginary sagittal plane passing through the gallbladder and IVC.The liver is important as it receives the venous drainage from the GI tract, its accessory organs, and the spleen via the portal vein. The liver serves the following important functions:• Storage of energy sources (glycogen, fat, protein, and vitamins)• Production of cellular fuels (glucose, fatty acids, and keto acids)• Production of plasma proteins and clotting factors• Metabolism of toxins and drugs• Modification of many hormones• Production of bile acid• Excretion of substances (bilirubin)• Storage of iron and many vitamins• Phagocytosis of foreign materials that enter the portal circulation from the bowel The liver is a derivative of the foregut and receives its arterial supply from branches of the celiac trunk. Its right and left hepatic arteries arise from the hepatic artery proper, a branch of the common hepatic from the celiac trunk. The hepatic artery proper lies in the hepatoduodenal ligament with the common bile duct and portal vein.