Arterial & Venous Thrombosis Flashcards
What prevents the formation of blood clots in a normal body?
Laminar flow - cells travel in the centre of arterial vessels & don’t touch the sides
Endothelial cells - line vessels, not ‘sticky’ when healthy
What is thrombosis?
The solidification of blood contents that forms within the vascular system during life
How does a thrombus form?
-damage to endothelial cells in the vessel causes some of the cells to lift away from the vessel wall
-collagen is exposed
-platelets stick to exposed collagen
-platelets release chemicals which cause platelet aggregation
-platelt aggregation starts coff cascade of clotting proteins in the blood
-erythrocytes trapped within aggregating platelets
-clotting factors join erythrocytes & platelets
-clotting cascade forms fibrin (large protein molecule) which forms the clot
-+ve feedback loop -> can end up forming a thrombus (thrombosis) -> thrombus can block artery
What are the 3 things which can cause thrombosis?
-change in vessel wall
-change in blood flow
-change in blood constistuents
How does cigarette smoking cause thrombosis?
-endothelial cell injury
-change in vessel wall
-change in blood flow over injured/absent cells
What can be used to reduce the risk of thrombosis?
-aspirin (low dose)
-anticoagulants, eg. heparin (low dose subcutaneous heparin), warfarin
-early mobilisation after surgery
How does aspirin reduce the risk of thrombosis?
Inhibits platelet aggregation
What is an embolism?
The process of a solid mass in the blood being carried through the circulation to a place where it gets stuck & blocks the vessel
What is an embolus?
Mass of material in the vascular system able to become lodged within a vessel & block it
What is the common cause of an embolus?
-usually caused by a part of a thrombus that has broken off & circulates in the bloodstream
-only small vessels can become blocked
What are the less common causes of an embolus?
-air - pressurised systems of intravenous fluids/bloods - especially in infants/children
-cholesterol crystals from atheromatous plaques
-tumour
-amniotic fluid (rare in pregnant women with precipitate labour)
-fat (severe trauma with fractures)
What happens if an embolus enters the venous system?
-it will travel to the vena cava
-lodge in the pulmonary arteries
-the lungs act as a filter for venous emboli - bc the blood vessels split down to capillary size - too small for the embolus to travel through - therefore the venous emboli cannot enter the arterial circulation
What happens if an embolus enters the arterial system?
-the embolus can travel anywhere downstream of its entry point
What is ischaemia?
Reduction of blood flow to a tissue without any other implications
What is infarction?
Reduction of blood flow to a tissue that is so reduced that it cannot even support mere maintenance of the cells in that tissue so they die
