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
What is end arterial supply?
An organ that only receives blood supply from one artery.
-problematic when a thrombus forms bc the whole blood supply to that organ is cut off -> infarction
Give 3 organs which have multiple arterial supplies
1) Lungs - supplied by pulmonary arteries & bronchial arteries
2) Liver - supplied by portal vein & hepatic artery
3) Parts of the brain - supplied by circle of Willis
What is atherosclerosis?
-degeneration of the walls of arteries
-caused by accumulated fatty deposits & scar tissue
-leading to restriction of the circulation & risk of thrombosis
What is atheroma?
The fatty material which forms deposits in the arteries
What is the most common cause of embolus?
Thrombus
Where would a thrombus in the LAD coronary artery cause infarction?
Anterior wall of L ventricle
