Which organ produces clotting factors?

The liver is the primary organ responsible for producing the majority of clotting factors involved in the coagulation cascade. Most coagulation factors — including fibrinogen (factor I), prothrombin (factor II), and factors V, VII, IX, X, XI, and XII — are synthesized by hepatocytes. Several of these factors, specifically II, VII, IX, and X, are vitamin K–dependent and require vitamin K for their activation through carboxylation. This is why liver disease and vitamin K deficiency both result in coagulopathy and increased bleeding risk. The clinical significance is substantial: patients with cirrhosis or hepatic failure often have prolonged prothrombin times because the liver can no longer produce adequate clotting factors. The pancreas produces digestive enzymes and hormones such as insulin and glucagon but does not manufacture clotting factors. The spleen plays a role in filtering blood and storing platelets, and it can destroy defective red blood cells, but it does not synthesize coagulation proteins. The kidneys regulate blood pressure, fluid balance, and erythropoietin production, but they are not a source of clotting factors. Therefore, the liver's central role in clotting factor synthesis makes it the correct answer.