Haemostasis and Thrombosis Flashcards
Define haemostasis.
Functions to limit blood loss
Vasocontriction > platelet plug > clot formation
Define Thrombosis.
occlusion/blockage of a blood vessel by a clot or platelet clump
What mechanisms normally suppress blood coagulation and platelet activation?
- non thrombogenic surface of endothelium
- endothelium produces PGI2 and NO which inhibits platelet aggregation
- NO produced also inhibits adhesion of platelets to vascular wall
- presence in plasma of natural anticoagulants- antithrombin III
What is the fibrinolytic system?
the physiological repair system for removing blood clots.
It involves the generation of the enzyme plasmin which digests fibrin.
Describe the fibrinolytic system.
plasminogen binds to fibrin > the tissue plasminogen activator converts that to plasmin > plasmin converts fibrin polymer into soluble degradation products
What is venous thrombosis? and what is its therapy?
Blood clot forms in deep veins, particularly of the legs
Therapy- anticoagulant drugs
What is arterial thrombosis? and what is its therapy?
platelets aggregate at site of ruptured plaque and clot encapsulates it
therapy- dissolve clots by fibrinolytics (immediate) or anti-platelet drugs (long term)
What are blood clotting disorders?
deficiency of a clotting factor can lead to uncontrolled bleeding. The deficiency may arise through reduced production or a mutant version of the clotting factor.
Give examples of blood clotting disorders.
1) Von Willebran disease- deficiency of Von Willebrand factor- binds to and stabilises factor VIII and binds platelets to collagen
2) Haemophilia A- deficiency of factor VIII (8)
3) Haemophilia B- deficiency of factor IX (9)
4) Haemophilia C- deficiency of factor XI (11)
What disorders are restricted to males and why?
Haemophilia A and B are restricted to males as factors VIII and IX are located on the X chromosome.
What is the treatment for blood disorders?
Replacement of deficient factor (derived from plasma or recombinant)
