How does portal hypertension occur in cirrhosis?

Portal hypertension occurs in cirrhosis primarily due to impeded blood flow from the liver. In cirrhosis, the liver becomes scarred and fibrotic, which obstructs normal blood flow through the portal vein. The portal vein is responsible for carrying blood from the gastrointestinal tract and spleen to the liver. When this blood flow is impeded due to structural changes in the liver tissue caused by cirrhosis, the pressure in the portal venous system increases. This elevated pressure results in various complications, such as varices, ascites, and splenomegaly.

The other options do not accurately describe the mechanism of portal hypertension in cirrhosis. For instance, increased blood flow to the liver does not occur; rather, blood flow is reduced due to the obstruction. Excess bile production is unrelated to the development of portal hypertension and instead pertains to bile management within the liver. Lastly, high blood pressure in the arteries refers to systemic arterial hypertension, not specifically to the portal venous system, and does not directly relate to the changes seen in cirrhosis. Thus, the correct understanding of how portal hypertension develops in this context focuses on the impediment of blood flow due to liver damage and scarring.