5 Haemostasis, Thrombosis and Embolism Flashcards
What does successful haemostasis depend on? (4)
Vessel wall
Platelets
Coagulation system
Fibrinolytic system
What is haemostasis?
The ability to stop bleeding
How do blood vessels limit blood loss?
Constrict to limit blood flow
Describe the process of platelet aggregation
ATP => ADP
Thromboxane A2 causes platelet aggregation
Aided by 5HT and PF3
How is coagulation regulated? Give an example
By thrombin inhibitors
Antithrombin III
Protein C and S
What is fibrinolysis? How does it occur?
The breakdown of fibrin
Plasminogen is degraded to plasmin by plasminogen activators
Give an example of a plasminogen activator
Prostacyclin
Nitric Oxide
Thrombomodulin
What is ‘thrombosis’?
The formation of a solid mass of blood within the circulatory system.
Why do blood clots form?
Abnormalities of the vessel wall
Abnormalities of blood flow
Abnormalities of blood components
What are the features of an arterial thrombus?
Pale, granular, lines of Zahn, lower cell content
What are the features of a venous thrombus?
Soft, gelatinous, deep red, higher cell content
What occurs in lysis of thrombi?
Fibrinolytic system degrades the thrombus so blood flow is re-established
What is propagation of thrombi?
Progressive spread of thrombosis
Distally in the arteries and proximally in the veins
What is organisation of thrombi?
Ingrowth of fibroblasts and capillaries so lumen remains obstructed
What is ‘recanalisation’?
Bloodflow is re-established but incompletely as channels form through the thrombus
