Functions of the Liver“A healthy liver is a sign of a healthy body”Kareem AustinGroup 1April 11th 2010
What is the Liver? Dark/Reddish Brown, vital organ. Both metabolic and excretory. Largest internal organ and largest gland. Described as having a double blood supply Lies on the right side of the abdominal cavity beneath the diaphragm. In males it weighs from 1.4 to 1.6 kilograms, in females from 1.2 to 1.4 kilograms The Liver is extremely resilient.
Liver Structure Macroscopic/Gross structure At the macroscopic level, the liver is divided by fossae (fissures) on its surface into two major lobes, (left and right) and two smaller lobes (quadrate and caudate). It is connected to the diaphragm and abdominal walls by five ligaments: the membranous falciform (also separates the right and left lobes), coronary, right and left triangular ligaments, and the fibrous round ligament (derived from the embryonic umbilical vein).
Liver Structure cont’d Microscopic structure At the microscopic level, the liver consists of hexagonal shaped functional units called hepatic lobules. These consist mostly of hepatocytes (the most common type of liver cell) arranged in thin layers that radiate from the central canal (central vein) to the periphery of the lobule. Between the radiating rows of hepatocytes are small blood vessels called sinusoids. These receive oxygen-rich blood from the hepatic artery and nutrients from the intestines via the portal vein. The oxygen and nutrients diffuse through the capillary walls into the liver cells. Within the sinusoids are specialized macrophages called Kupffer cells that figure prominently in the recycling of old red blood cells. At the corners of each lobule is a complex, called the portal area, composed of branches of the hepatic portal vein, hepatic artery, bile duct and nerve. Bile drains from the hepatocytes by the many small bile ducts that unite to form the main bile duct of the liver, the hepatic duct. This joins the cystic duct, which leads from the gallbladder, to form the common bile duct, which drains into the duodenum. The central canal is a blood vessel in the middle of each lobule which receives blood from the hepatic portal vein and hepatic artery via the sinusoids and drains the blood into the hepatic vein.
Functional Units of Liver Lobules which are made up of hepatocytes Hepatocytes make up 70-80% of the liver’s mass Surrounded be interlobular veins (branches of hepatic vein that empty into the vena cava) Interlobular arterial branches (proper hepatic artery) Bile ductus- series of ducts form the common hepatic duct Bile canaliculi Canals of Hering Interlobular bile ducts Intrahepatic bile ducts left and right hepatic ducts
Functions of the Liver Metabolic Storage Excretory/Secretory Protective Circulatory Coagulation
Metabolic Functions Carbohydrate metabolism Gluconeogenesis (the synthesis of glucose from certain amino acids, lactate or glycerol ) Glycogenolysis and glycogenesis (breakdown of glycogen to glucose/ formation of glycogen from glucose) Hormone metabolism Synthesis of fatty acids, lipoproteins,cholesterol Ketogenesis (breakdown of keytones to fats) Protein Metabolism Synthesis of plasma proteins (albumin, globulin, fibrinogen) Urea synthesis (ammonia to urea) Red blood cell production (In the first trimester of the fetus)
Storage Functions Glycogen Vitamins A, D, E, K (fat soluable) B12 (water soluable) Iron Copper
Excretory/Secretory Bile – Water – Cholesterol – Bile pigments (Bilirubin and Biliverdin) – Anions of the Bile acids – Phospholipids (mainly lecithin) – Bicarbonate and other ions Insulin-like Growth Factor 1(IGF-1) Most blood proteins (save antibodies) are synthesis and therefore secreted by the liver Cholesterol, fatty acids (via lipoproteins)
Protective Function Purification, Transformation, and Clearance - The liver removes harmful substances (such as ammonia and toxins) from the blood and then breaks them down or transforms them into less harmful compounds. In addition, the liver metabolizes most hormones and ingested drugs to either more or less active products. Kupffer cells - ingest bacteria or other foreign material from the blood
Circulatory Function While the liver is technically part of the gastrointestinal system, it also plays an important role in blood circulation. The liver has been called the "antechamber of the heart" because it collects and processes all of the gastrointestinal blood through the portal vein and delivers it to the right side of the heart. The liver receives blood through two vascular systems, the portal vein and hepatic artery.
Coagulator Functions Production and secretion of coagulation factors fibrinogen I prothrombin II Factors (V, VII, IX, X, XI) protein C protein S antithrombin.
Liver Enzymes cont’d Liver enzymes are proteins that help to speed up a chemical reaction in the liver. Liver function tests are blood tests that are used to evaluate various functions of the liver – for example, metabolism, storage, filtration and excretion, which are often performed by liver enzymes. However, not all liver function tests are measures of enzyme function
Pathology A common sign of a damaged liver is jaundice, a yellowness of the eyes and skin. This happens when bilirubin, a yellow breakdown product of red blood cells, builds up in the blood. Among the many diseases of the liver are: Hepatitis (inflammation of the liver), caused mainly by various viruses but also by some poisons, autoimmunity, or hereditary conditions. Cirrhosis is the formation of fibrous tissue in the liver, replacing dead liver cells. The death of the liver cells can for example be caused by viral hepatitis, alcoholism or contact with other liver-toxic chemicals. Hemochromatosis, a hereditary disease causing the accumulation of iron in the body, eventually leading to liver damage.
Pathology cont’d Cancer of the liver (primary hepatocellular carcinoma or cholangiocarcinoma and metastatic cancers, usually from other parts of the gastrointestinal tract). Wilsons disease, a hereditary disease which causes the body to retain copper. Primary sclerosing cholangitis, an inflammatory disease of the bile duct, autoimmune in nature. Primary biliary cirrhosis, autoimmune disease of small bile ducts Budd-Chiari syndrome, obstruction of the hepatic vein. Gilberts syndrome, a genetic disorder of bilirubin metabolism, found in about 5% of the population
Summary The liver is the largest internal organ in the human body The liver is extremely vital for our survival providing numerous functions. – Metabolising and detoxifying toxic material – Storage of vitamins, minerals and sugars – Synthesis and secretion of essential proteins and lipids – Production and secretion of bile A healthy liver is a sign of a healthy organism.