What is the extrinsic pathway of hemostasis?
The extrinsic pathway is the shorter pathway of secondary hemostasis. Once the damage to the vessel is done, the endothelial cells release tissue factor which goes on to activate factor VII to factor VIIa. Factor VIIa goes on to activate factor X into factor Xa.
How is the extrinsic pathway activated?
The extrinsic pathway begins when there is injury to the endothelial tissue (i.e., skin tissue), exposing tissue factor (factor III) to the blood. Tissue factor then becomes bound with calcium and factor VIIa to activate factor X. Factor VII is present in the blood and requires vitamin K to be activated.
Why is it called extrinsic pathway?
Tissue factor is found in many of the cells of the body but is particularly abundant in those of the brain, lungs, and placenta. The pathway of blood coagulation activated by tissue factor, a protein extrinsic to blood, is known as the extrinsic pathway (Figure 1).
What is the necessity of extrinsic pathway?
Understanding how the extrinsic pathway of blood coagulation contributes to hemostasis and thrombosis may lead to the development of safe and effective hemostatic agents and antithrombotic drugs. The extrinsic pathway of blood coagulation is required for thrombosis.
What factors are involved in the extrinsic pathway?
Clotting factors involved in the extrinsic pathway include factors VII, and III. The common pathway includes clotting factors X, V, II, I, and XIII. Clotting factors can also be referred to outside of their Roman numeral designations.
What is the difference between primary and secondary hemostasis?
Primary hemostasis is a procoagulation clot forming process associated with the initiation and formation of the platelet plug. Secondary hemostasis also a procoagulation clot forming process and it is associated with the propagation of the clotting process via the intrinsic and extrinsic coagulation cascades.
What is secondary hemostasis?
Secondary hemostasis refers to the cascade of enzymatic reactions that ultimately results in the conversion of fibrinogen to fibrin monomers. Fibrin monomers are then cross-linked into insoluble strands that serve to stabilize the loose platelet clot formed in primary hemostasis.
What are components of secondary hemostasis?
Secondary hemostasis consists of the cascade of coagulation serine proteases that culminates in cleavage of soluble fibrinogen by thrombin (Figure 2). Thrombin cleavage generates insoluble fibrin that forms a crosslinked fibrin mesh at the site of an injury.