Homework SourseC7 Ciepkx Peellanerhutti SolutionAnswer The figure shows in
Solution
Answer:
The figure shows intrinsic and extrinsic pathway of blood clotting mechanism.
Extrinsic pathway steps:
Factor Xa is the common factor involved in both intrinsic and extrinsic pathways. Extrinsic pathway involves the factors: VII, X, tissue factor and calcium ions.
1. Activation occurs at the site of injury where tissue factor is present. Tissue factor helps in the conversion of factor VII to VIIa.
2. Factor VII is associated with prothrombin which is present in the blood plasma.
3. Factor VIIa cleaves arg-ile bond of factor X.
4. Factor VII, a Gla containing glycoprotein is a zymogen and activated by prothrombin and factor Xa.
5. Factor X activation is the link between extrinsic and intrinsic pathway.
6. Another link is the complex of factor VIIa and tissue factor in extrinsic pathway. They also activate factor X to Xa.
Intrinsic pathway:
It includes factors XII, XI, IX, VIII and X. In addition, it includes prekellikerin, kininogen, calcium ions and platelet phospholipids.
1. Components of the contact phase assemble on the activation surface, factor XII gets activated to XIIa due to proteolysis by kellikerin.
2. Factor XIIa attacks pre-kellikerin setting up reciprocal reaction activation.
3. Activated XIIa activates factor XI to XIa and also releases bradykinin from high molecular weight kininogen.
Additional steps:
1. Factor XIa activates factor IX to IXa (serine protease) in presence of calcium ions.
2. Activated factor IXa cleaves Arg-Ile bond of factor X to form Xa, a serine protease.
(Factor VIII is is a glycoprotein and not a protease precursor. It acts as a receptor for factor IXa and X on the platelet surface)
Final common pathway:
1. Factor Xa activates prothrombin to thrombin which then convert fibrinogen to fibrin.
2. The thrombin formed converts factor XIII to XIIIa which helps in cross linking of fiber polymers.
(The provided image was not clear. So, the detailed pathways have been discussed)
