The liver is a vital organ, plays a major role in metabolism with numerous functions in the human body, including regulation of glycogen storage, decomposition of red blood cells, plasma protein synthesis, hormone production, and detoxification. It is an accessory digestive gland and produces bile, an alkaline compound which aids in digestion via the emulsification of lipids.
The liver is a reddish brown wedge-shaped organ with four lobes of unequal size and shape. A human liver normally weighs 1.44–1.66 kg (3.2–3.7 lb). Located in the right upper quadrant of the abdominal cavity, it rests just below the diaphragm, to the right of the stomach and overlies the gallbladder.
The study of microscopic anatomy, shows two major types of liver cell: parenchymal cells and non-parenchymal cells. 70–85% of the liver volume is occupied by parenchymal hepatocytes. Non-parenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume. The liver sinusoids are lined with two types of cell, sinusoidal endothelial cells, and phagocytic Kupffer cells. Hepatic stellate cells are non-parenchymal cells found in the perisinusoidal space, between a sinusoid and a hepatocyte. Additionally, intrahepatic lymphocytes are often present in the sinusoidal lumen.
The central area or hilum, known as the porta hepatis is where the common bile duct, hepatic portal vein, and the hepatic artery proper enter the liver. The duct, vein, and artery divide into left and right branches, and the areas of the liver supplied by these branches constitute the functional left and right lobes.The functional lobes are separated by the imaginary plane, Cantlie’s line, joining the gallbladder fossa to the inferior vena cava. The plane separates the liver into the true right and left lobes. The middle hepatic vein also demarcates the true right and left lobes. The right lobe is further divided into an anterior and posterior segment by the right hepatic vein. The left lobe is divided into the medial and lateral segments by the left hepatic vein.
The liver receives a dual blood supply from the hepatic portal vein and hepatic arteries.