The basic functional unit of the liver is called the lobule. This hexagonal structure, which measures one to two millimeters in diameter, is composed of hepatocytes, the liver cells organised around a central vein. The central vein plays a crucial role in draining blood from the liver. Each corner of the hexagonal lobule houses a portal triad, a key feature in the liver's intricate structure.

The portal triad consists of three main components. The first is a portal venule, which supplies blood and nutrients from the portal system, transporting substances absorbed from the gastrointestinal tract. The second component is a hepatic arteriole, which provides oxygenated blood from the arterial system, essential for the metabolic activities of hepatocytes. The third component is a bile canaliculus, a small duct that drains bile produced by hepatocytes into the bile duct, eventually leading to the gallbladder and intestine for digestion.

This organisation allows for efficient processing of blood and production of bile. Blood flows from the portal venule and hepatic arteriole through sinusoids, which are channels that run between hepatocytes. During this passage, hepatocytes extract nutrients, detoxify substances, and secrete bile. The processed blood then drains into the central vein and exits the liver via the hepatic veins, while bile flows through the bile canaliculi into the bile ducts. This intricate system ensures the liver can perform its vital functions effectively.