Thrombosis And Embolism Flashcards
What is thrombosis
Process leading to formation of thrombus
What is a thrombus
Blood clot
Solid mass made of blood constituents which have aggregated together in flowing blood of the lumen of a blood vessel
What are the main constituents of a thrombus
Platelets and fibrin
What types of thrombosis are there?
Physiological and pathological
When is thrombosis a normal mechanism?
Preventing bleeding when a vessel wall is breached
When does thrombosis become pathological
When it is not controlled by fibrinolysis
Describe normal thrombosis
Vessel wall breached
Circulating platelets aggregate to plug gap
Platelets release factors which trigger cascade
Cascade converts fibrinogen to fibrin
Fibrin bind together platelets and entrap WBCs and RBCs
What is fibrinolysis
Breaking down of fibrin so the thrombus dissolves
Plasmin is the enzyme
Broken down products are the fibrin degradation products
What occurs to control the side of the thrombus
Plasminogen converted to plasmin by plasminogen activator (tissue plasminogen activator)
Plasminogen and t-PA bund to fibrin
t-PA converts nearby plasminogen to plasmin which begins to degrade the fibrin
Describe pathological thrombosis
Occurs when thrombus enlarges beyond vessel healing requirements and continues to grow
Beyond certain thrombus size and rate of development, intrinsic fibrinolytic system is incapable of controlling size of thrombus
How does the thrombus grow in pathological thrombus?
Accretion of layer upon layer
If it continues unrestrained, reddish-brown mass is produced in vessel
What are D-dimers?
Breakdown product of a fibrin mesh, stabilised by factor XIII
What factors predispose thrombus formation?
- Damage to vessel wall (endothelium)
- Stasis (slow or turbulent)
- Change in character of blood (increased platelets, RBCs)
Where does pathological thrombosis occur?
Arteries
Veins
Heart
Most prominent predisposition factor of arteries?
Vessel wall damage
Most prominent predisposition factor of veins?
Stasis