Liver architecture in healthy liver and fibrosis. (A) In normal liver, hepatocytes are arranged in rows radiating outwards from the central vein, toward the edge of the lobule. The gaps between the hepatocyte rows are known as sinusoids which are lined with endothelial cells, and contain Kupffer cells, hepatic stellate cells, and contain extracellular material such as the non fibrogenic type IV collagen. Hepatic portal vein, hepatic artery and biliary tree are the three major vessels feeding into the sinusoids and the exchange of blood gases, nutrients and other signaling molecules occurs in the sinusoids. (B) Injury to hepatocytes due to any of several causes such as alcohol, drug, genetic predisposition, etc., activates the wound healing fibrogenic response. Chronic injury to the hepatocytes and chronic activation of the fibrogenic pathway in the liver leads to synthesis of fibrogenic type I collagen by the Hepatic stellate cells and its deposition within the sinusoids. Deposition around the central vein and around the portal vein leads to increase in vascular resistance and portal hypertension. Compensatory mechanisms such as esophageal varices and ascites