11. Atheroma, Thrombosis and Embolism Flashcards
what is atherosclerosis
degeneration of arterial walls characterised by fibrosis, lipid deposition and inflammation, which limits blood circulation and predisposes to thrombosis, i.e. accumulation of fat on the vessel wall, attracts thrombosis
vessels which are vulnerable to atherosclerosis
aorta coronary vessels popliteal arteries neck vessels circle of willis sites of bifurcation
why are areas of bifurcation at a higher risk of atherosclerosis?
thi is because they are sites of turbulent flow. Blood tends to come in contact with vessel walls here. linear flow ensures blood flows in the centre of the vessel
what are the risk factors for atherosclerosis?
old age men women after menopause family history hyperlipidaemia (especially LDL) hypertension smoking type II diabetes rare causes - homocysteine, stress, CRP
what is the pathophysiology of atherosclerosis?
- endothelial injury - makes the vessel wall more permeable to inflammatory agents and lipids
- fatty streak - lipid accumulates in the intimate of the vessel. prior injury also causes vessel wall to attract inflammatory cells, which will ingest the fat. won’t be able to handle too much fat in them, will form foam cells
- formation of the atherosclerotic plaque - foam cells secrete chemokines, attract more inflammatory cells and creat more permeability. also attract lymphocytes and cause smooth muscle proliferation and fibrosis at the site of accumulation
what is the atherosclerotic plaque made up of?
fat + extracellular material + leukocytes + smooth muscle
has a fibrous cap, shoulder, and a dead, central core
what are the consequences of atherosclerosis?
- occlusion of blood supply
- weakens vessel wall, could lead to aneurysms
- erosion by turbulence of blood flow or leakage from shoulder leading to formation of thrombosis
what is thrombosis?
solidification of blood contents formed IN the vessel DURING life
what are the differences between a clot and a thrombus?
clot - stagnant blood clotting cascase elastic, adopts vessel shape could occur after death thrombus platelet dependent firm within the body during life
what are platelets?
fragments of megakaryocytic, don’t contain a nucleus
what are the main active components of platelets?
alpha granules - contain substances required for the production of fibrin
dense granules - contain chemotactic chemicals, to attract other platelets
how are platelets activated?
exposure to sub endothelial collagen. this only happens when the endothelium is damaged. platelets bind to this collagen, produce fibrin and trap RBCs.
what are the 3 factors in virchow’s triad?
- change in the intimal surface of the vessel
- change in the patter of blood flow
- change in blood constituents
why are thrombi usually formed downstream from atheroma?
atherosclerosis causes turbulent blood flow once blood has passed by it, making it more likely to form a thrombus
examples of changes in constituents of blood
infection
malignancy
inherited thrombogenic factors
high levels of oestrogen (OCP, pregnancy)
