| The liver is the largest solid organ in the body and, in adults, weighs about 1500g. It occupies the right upper quadrant of the abdominal cavity, lying below the diaphragm and protected by the rib cage. Approximately 75% of the blood flow to the liver is supplied by the portal vein, which arises from the intestine. Blood leaving the liver enters the venous system through the hepatic vein. The biliary component of the liver comprises the gall bladder and bile ducts.
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| The microscopic structure of the liver facilitates the exchange of metabolites between hepatocytes and plasma
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| Under the microscope, the substance of the liver is composed of a very large number of lobules, each of which is poly-hedral in shape (Fig. 28.2). Blood sinusoids arise from the terminal branches of the portal vein and interconnect and interweave through these sheets of hepatocytes before joining the central lobular vein.
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| Sinusoids are lined by two cell types. The first are vascular endothelial cells, which are loosely connected one with another, leaving numerous gaps, and thus form a net-like lining to the sinusoids. Moreover, there is no basement membrane between the endothelial cells and the hepatocytes. This structural arrangement facilitates the exchange of metabolites between hepatocyte and plasma. The second type of sinusoidal cell, known as Kupffer cells, are mononuclear phagocytes; they are generally found in the gaps between adjacent endothelial cells.
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