| The liver has a central role in metabolism, because of both its anatomical placement and its many biochemical functions. It receives venous blood from the intestine, and thus all the products of digestion, in addition to ingested drugs and other xenobiotics, perfuse the liver before entering the systemic circulation. The hepatic parenchymal cells, the hepatocytes, have an immensely broad range of synthetic and catabolic functions, which are summarized in Table 28.1. The liver has important roles in the regulation of carbohydrate and lipid metabolism, in amino acid metabolism, in the synthesis and breakdown of plasma proteins, and in the storage of vitamins and metals; it also has the ability to metabolize, and so detoxify, an infinitely wide range of xenobiotics. The liver also has an excretory function, in which metabolic waste products are secreted into a branching system of ducts known as the biliary tree, which in turn drains into the small intestine; the biliary constituents are then excreted in feces.
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| The liver has a substantial reserve metabolic capacity; mild liver disease may cause no symptoms, and be detected only as biochemical changes in the blood. However, the patient with severe liver disease has a yellow pigmentation of the skin (jaundice), bruises readily, may bleed profusely, has an abdomen distended with fluid (ascites), and may be confused or unconscious (hepatic encephalopathy) (Fig. 28.1). This chapter will describe the specialized metabolic functions of the liver and the abnormalities that occur in liver disease.
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