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Liver, structure and function

Detailed lecture on how the structure and function of the liver are related. The liver is the largest solid organ in the body with only the skin having a greater total mass. In men it normally weighs 1.4-1.8 kg and 1.2-1.4 kg in women. The liver is involved in many of the biochemical processes which are necessary within the body. This is why the liver is sometimes referred to as the ‘chemical factory’ of the body. It is accurate to classify the liver as an exocrine gland as it produces approximately 500 mls of bile per day. This bile is secreted from the liver via the right and left hepatic ducts which merge to form the common hepatic duct. The cystic duct transports bile from the common hepatic duct into the gallbladder where it is stored and concentrated. The same cystic duct carries bile out of the gallbladder into the common bile duct. The pancreatic duct merges with the common bile duct before it communicates with the duodenum. This arrangement means that bile and pancreatic juices both enter the duodenum together via the hepatopancreatic sphincter (of Oddi) and major duodenal papilla. The major duodenal papilla is an elevation on the internal wall of the duodenum. Within the lobes of the liver are numerous lobules, separated from each other by connective tissue. Lobules are usually 5 or 6 sided and are cylindrical. At the corners of the lobules are branches of the HPV, hepatic artery and bile ducts. Collectively, these 3 vessels are referred to as a triad. A normal liver contains between 50,000 to 100,000 lobule units which vary in diameter from 0.8 to 2 mm. Lobules are the functional units of the liver. Individual liver cells are called hepatocytes. In an individual lobule, hepatocytes are arranged around a central vein, like spokes around a hub in a wheel. It is a radial arrangement of cells. Typically the hepatocytes are arranged in a row, two cells thick. These two rows of cells are described as a hepatic cellular plate.