The Liver

The liver has several funtions to support digestion and homeostasis. Beside the detoxification of a variety of metabolites, the liver also synthesizes proteins and produces biochemicals for digestion and growth. Further functions in metabolism are the decomposition of red blood cells, the production of hormones and the regulation of glycogen. According to the highly specialized functions of the liver, its tissue is similarly specialized and mainly consists of hepatocytes which are specialized to sythesize and breakdown small and complex molecules.

Around 400 genes are specifically expressed in the liver, of which around 150 are highly specific for the liver tissue and a large proportion being expressed primarily in hepatocytes. Proteins translated in the liver mainly represent plasma proteins which are secreted into the blood, others constitute liver enzymes such as HAO1 and RDH16, proteins involved in bile synthesis or transporter proteins involved in the metabolism of drugs. Some of the most commonly studied examples are e.g. apolipoprotein A II, coagulation factors F2 and F9, complement factor related proteins, and the fibrinogen beta chain protein.

Viral infection with e.g. Hepatitis A, B, C, D, and E are a common cause for liver inflammation and chronic infections are the main cause for the develeopment of liver cancer. Other liver disorders, for example alcoholic liver diseases like alcoholic hepatitis, fatty liver, or cirrhosis can be caused by excessive alcohol consumption. There are also many pediatric liver diseases, such as alpha-1 antitrypsin deficiency,  Langerhans cell histiocytosis and hepatic hemangioma. However, the liver usually only produces symptoms after massive damage since the organ has a great regenertaion capacity.