Thrombosis and Embolism Flashcards
What is thrombosis
Process leading to the formation of a thrombus
What is a thrombus
Solid mass composed of blood constituents which have aggregated together in flowing blood in the lumen of a blood vessels;
What are the main constituents of a thrombus
Platelets and fibrin
What is thrombosis limited by
Fibrinolysis
When does thrombosis become a pathological process
When it isn’t controlled by fibrinolysis
How Is a thrombus formed
- VEssel wall is breached
- Circulating platelets aggregate to plug the gap
- Platelets release factors which trigger coagulation cascade
- Coagulation cascade converts fibrinogen to large molecules of insoluble fibrin
- Long fibrin molecules bind together platelets and entrapped red and white cells
What controls the size of the thrombus
Fibrinolysis
What holds the thrombus together
FIbrin
What is the active enzyme which fragments fibrin
Plasmin
What is a measure of thrombosis
D-Dimer test
What inactive proenzyme does plasma contain
Plasminogen
What does plasminogen become
Plasmin
What is plasminogen converted to plasmin by
Plasminogen activators
-particularly tissue plasminogen activator (secreted by endothelial cells)
What happens in fibrinolysis
When fibrin is formed, plasminogen and tissue plasminogen activator bind to it. The tissue plasminogen activator converts nearby plasminogen to plasmin which degrades the fibrin
What are D-dimers and when’re they elevated
Breakdown product of a fibrin mesh
-Increased blood levels in thrombosis
What factors contribute to the formation of a thrombus
- Damage to vessel wall
- Slow or turbulent blood flow
- Change in character of blood
How does the character of blood change for there to be an increase in the chance of a thrombus
- Increased platelets
- Increased red cell numbers
- Increased viscosity
Main cause of thrombus formation in arteries
Vessel wall damage
MAin cause of thrombus formation in veins
Stasis of blood
Main cause of thrombus formation in ventricles
Chamber wlall damage
Main cause of thrombus formation in atrium
Stasis of blood
Main cause of thrombus in heart valves
Valve surface damage
What does a thrombus in the artery leading to the heart lead to
Angina
What does a thrombus in a coronary artery lead to
Heart attack
What does a thrombus in an artery leading to the brain lead to
Stroke
In a vein, what does an occlusion prevent and so what does this lead to
Prevents drainage of tissues. So blood pools and cannot escape. This leads to congestion and infarction
What is organised thrombus
- New vessels grow into the thrombus
- VAscular granulation tissue develops
- Fibroblasts invade and deposit collagen
- Fibrovascular granulation tissue develops
What is recanalisation
When vessels link up inside the thrombus
What is embolism
Transference of abnormal material by the blood stream with eventual impaction of the material in a vessel distal to its site of origin
What are the most important materials to embolism
Thrombus and cancer cells
What does a thrombus in an artery or the left side of the heart embolism into
systemic arterial system
Where may a thrombus in an artery or the left hand side of the heart go to
Brain Lower limbs Mesentric arteries Renal arteries Splenic artery
Where would a thrombus in a systemic vein eventually embolise
To a pulmonary artery branch
What would a pulmonary artery branch thrombus be called
Pulmonary embolus
What would a small embolus in a pulmonary artery lead to
small peripheral lung infarct
What would a large embolus in a pulmonary artery branch lead to
Sudden death
To measure tissue heat, what can you measure
Level of lactate
What are some other materials which would embolise
- Fat and marrow
- Air
- Nitrogen
- Amniotic fluid
How does nitrogen embolism occur
When you go deep underwater, the solubility of your blood to nitrogen increases so more nitrogen dissolves in bloodstream.
IF you go up from the deep water too quickly, the nitrogen becomes ‘bubbly’ and you get bubbles in blood
How does an amniotic embolism occur
Placenta peels off and the amniotic fluid ends up in the blood
squamous cells (petal skin cells) which are present in the amniotic fluid can block the blood vessels
Difference between infarction and necrosis
Infarction is tissue death (necrosis) due to inadequate supply of oxygen
Signs of a previous myocardial infarction
Scarring (white)
