What is the difference between intrinsic and extrinsic pathway

The intrinsic pathway is activated by the binding of factor XII to a negatively-charged foreign surface that is exposed to blood.

Thrombin converts fibrinogen to fibrin. Platelets are trapped inside a fibrin mesh, forming a blood clot. Extrinsic pathway refers tomultiple cascades of protein interactions activated by damaged external surfaces. Factor III and thromboplastin are involved in the extrinsic pathway. The extrinsic pathway is shorter than the intrinsic pathway, and it is quicker than the intrinsic pathway.

The process of blood clotting is shown in figure 2. Thromboplastin is a tissue factor TF that is not exposed to the blood under normal conditions. But under vascular or endothelial cell injury, the exposure of thromboplastin activates factor VIIa and phospholipids to be converted into factor IX.

Finally, factor X is activated by the factor Xa from the extrinsic pathway. Intrinsic Pathway: Intrinsic pathway refers to multiple cascades of protein interactions activated by a trauma inside blood vessels. Extrinsic Pathway: Extrinsic pathway refers to multiple cascades of protein interactions activated by damaged external surfaces. Intrinsic Pathway: Intrinsic pathway is activated by internal trauma. When prothrombin activator is activated, it facilitates the conversion of prothrombin into thrombin.

Thrombin catalyzes the polymerization of fibrinogen into fibrin, which is the basic component of the blood clot. Intrinsic pathway of blood clotting is a slow process which completes within several minutes. But it is an important process in organisms. Extrinsic pathway is another way of blood coagulation. This system is activated by vascular tissue trauma or surrounding extra-vascular tissue trauma.

These external factors release a complex of several factors which is collectively known as tissue factor or tissue thromboplastin or factor III. Tissue factor is a protein found in many tissues of the body, including brain, lungs, and placenta. Tissue factor is the main component which activates the extrinsic pathway of blood clotting.

Under normal conditions, blood is not contacted or exposed to these tissue factors. Factor IXa activates factor X into factor Xa. Factor Xa is the prothrombin activator which is responsible for the conversion of prothrombin into thrombin. Once prothrombin activator is formed, the common pathway starts and blood coagulation proceeds.

Extrinsic pathway is quicker than intrinsic pathway. Within about 15 seconds, it completes blood coagulation. Blood coagulation refers to the process of forming a clot to stop bleeding. A blood clot is mainly formed from fibrin and platelets. Formation of fibrin is catalyzed by the enzyme called thrombin. Thrombin formation is facilitated by prothrombin activator made from two pathways named intrinsic and extrinsic pathways. Both intrinsic and extrinsic pathways activate prothrombin activator to catalyze the conversion of prothrombin into thrombin.

The difference between intrinsic and extrinsic pathways in blood clotting depends on their initiation factors; extrinsic pathway is initiated after the release of a tissue factor to the blood due to a trauma to the vascular wall or surrounding tissues while intrinsic pathway is initiated when collagen contacts with the blood due to blood trauma.

You can download PDF version of this article and use it for offline purposes as per citation notes. Furie, Bruce. Available here. Thank You so much Dr. Thank you very much. Thank you very much Professor. Is it that, while testing the extrinsic pathway by PT-INR, a small amount of fibrin is formed and the test comes to a finish before the extrinsic arm is inhibited by thrombin and before the intrinsic pathway takes over? Your email address will not be published. Notify me of follow-up comments by email.

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Share this: Twitter Facebook. More pathology! Perfect answer to the question. You broke it down to the basics. Thanks Dr Krafts. Janarthan Rama Murti on July 29, at am. Jack Simmons on August 3, at pm. Now it is starting to make sense.

Kristine on August 3, at pm. Good analogy, Ehsam. You made this seem so simple! Joyce on September 23, at pm. Kristine on September 27, at am. Kristine on December 24, at pm. Ana Palmeiro on December 30, at pm. I loved reading this, you make it sound so fun!

Keep it up! Genevieve Blais on December 30, at pm. Mahesh on February 15, at am. Kristine Really awesome. Wills on March 1, at pm. Chikaodiri on April 30, at pm.

Wow so simplistic. Thank you Dr. Kristine on April 30, at pm. So glad you liked it!