Liver

The liver is an organ in vertebrates, including humans. It plays a major role in metabolism and has a number of functions in the body including detoxification, glycogen storage and plasma protein synthesis. It also produces bile, which is important for digestion. Medical terms related to the liver often start in hepato- or hepatic from the Greek word for liver, hepar.

Physiology

The various functions of the liver are carried out by the liver cells or hepatocytes.

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• The liver produces and excretes bile required for food digestion. Some of the bile drains directly into the duodenum, and some is stored in the gallbladder.
• The liver performs several roles in carbohydrate metabolism:
• Gluconeogenesis (the formation of glucose from certain amino acids, lactate or glycerol)
• Glycogenolysis (the formation of glucose from glycogen)
• Glycogenesis (the formation of glycogen from glucose)
• The breakdown of insulin and other hormones
• The liver also performs several roles in lipid metabolism:
• Cholesterol synthesis
• The production of triglycerides (fats).
• The liver produces coagulation factors I (fibrinogen), II (prothrombin), V, VII, IX, and XI, as well as protein C, protein S and antithrombin.
• The liver breaks down hemoglobin (bile pigments are its metabolites), toxic substances and most medicinal products. This sometimes results in toxication, when the metabolite is more toxic than its precursor.
• The liver converts ammonia to urea.
• The liver stores a multitude of substances, including glucose in the form of glycogen, vitamin B12, iron, and copper.
• In the first trimester fetus, the liver is the main site of red blood cell production. By the 42nd week of gestation, the bone marrow has almost completely taken over that task.

Producing an artificial organ or device capable of emulating all functions of the liver is outside the reach of science in the foreseeable future. Some functions can be emulated by liver dialysis, an experimental treatment for liver failure.

Related Topics:
Liver dialysis - Liver failure

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