Liver and biliary system

The liver is the body's largest organ, weighing about 1.5 kgs, or 2.5% of body weight. Major functions involve the uptake of nutrients and other substances from the intestine, processing (metabolising), storing or distributing these to blood and bile. The liver is also important in removing unwanted or harmful chemicals (detoxification) including chemicals produced in the body, unwanted chemicals taken into the body (eg carcinogens), and medications. The liver is the 'powerhouse' of the body.

Functionally, the liver is divided into lobes and segments, each with its own blood supply. It is like a large vascular 'sponge' with an extensive network of blood vessels. Blood entering the liver contains nutrients and other products which are extracted and processed. As a consequence, blood leaving the liver contains less of these substances. Liver cells - hepatocytes - are the liver's main functional units. These produce bile, distribute nutrients from the blood, store fat-soluble vitamins, and play important roles in detoxification. 

The liver and biliary system produce bile and transport it to the small intestine, where it breaks up fats and other components of diet, and aids the digestion and absorption of these nutrients. About a litre of bile is produced daily. This leaves the liver via several ducts leading into the common hepatic duct, which joins the common bile duct (draining the gallbladder) and enters the small intestine. Excess bile is stored in the gallbladder, a green muscular sac approximately 10cm long attached to the lower part of the liver. If the gallbladder has been removed, bile is stored in the bile ducts which expand in size to hold the extra fluid.