Question

What are the factors that influence blood clot formation, control, and dissolution?

• Describe or illustrate the intrinsic and extrinsic pathway for clot formation
• Describe or illustrate the positive and negative feedbacks
• Indicate the role of WBC in the management of clotting

Answer 1

Factors influencing blood clot formation are called clotting factors. Clotting factors in good fibrinogen, prothrombin, tissue thromboplastin, calcium ions, proaccelerin, proconvertin, antihemophilic factors A,B,C; hageman factor, fibrin stabilizing factor, high molecular weight kirinogen, Pre-kallikrein, Kallikrein, Platelet phospholipid etc.

The factor influencing intrinsic pathway of clotting is factor 12 which is hageman factor by exposing to collagen and extrinsic pathway is initiated by release of tissue thromboplastin from the damaged tissue.

The factors that control the blood clot formation are protein C, protein S, protein Z, which act by inactivating clotting factors. Thrombomodulin please the clotting factor and control clotting and antithrombin-III inhibits the clotting factors.

Tissue factor pathway inhibitor and protein Z dependent protease inhibitor also control clotting. Anticoagulant are the substances used for the treatment of thrombosis thus dissolve the clots.

Oral anticoagulants are warfarin, dicoumarol, heparin sulfate and intravenous anticoagulants include heparin and low molecular weight heparins.

Positive Feedback:

Activation of one clotting factor which acts as an enzyme to activate next clotting factor in the coagulation cascade thus resulting in the formation of the clot.

Negative Feedback:

Negative feedback in coagulation cascade is brought about by thrombin which is the major mediator that initiate the process of anti clotting mechanism by fibrinolysis and controls the of the clot.

Role of WBC in management of clotting:

• WBC regulate the events leading to thrombin formation.
• Monocytes in the blood interact with the wide variety of cells in the blood and the vascular endothelium thus regulating the clot formation.
• Leukocytes like monocytes and neutrophils are involved in fibrinolysis and clot resolution and regulate the clearance of platelets and other clotting factors.