What is the difference between thromboplasin and factor Xa? I have in my notes that they both convert prothrombin to thrombin.

Thromboplastin and factor Xa are both involved in the process of blood clotting, but they have different roles.

Thromboplastin, also known as tissue factor, is a protein found on the surfaces of damaged cells, specifically in tissues outside of blood vessels. When injury occurs, thromboplastin is released, initiating the clotting cascade. Thromboplastin activates factor VII, which leads to the formation of a complex called the prothrombinase complex.

Factor Xa, on the other hand, is a key enzyme in the clotting cascade that converts prothrombin to thrombin. Prothrombin is a protein precursor to thrombin, which is the active enzyme responsible for converting fibrinogen to fibrin. Factor Xa is formed by the prothrombinase complex after activation of factor X through the intrinsic or extrinsic pathway.

To summarize, thromboplastin initiates the clotting process by activating factor VII, while factor Xa, formed by the prothrombinase complex, converts prothrombin to thrombin.

To find this information, you can refer to reliable sources such as textbooks or medical websites that explain the steps of blood clotting in detail. Additionally, understanding the definitions and functions of each component will help clarify the differences between thromboplastin and factor Xa.