10 - Atherosclerosis Flashcards
What is the definition of atherosclerosis?
- Accumulation of intracellular and extracellular lipid in the intima and media of large and medium sized arteries
- Leads to necrotic atheroma in middle and plaque can calcify
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What part of the aorta is atherosclerosis most likely to occur in?
Abdominal rather than thoracic
What is arteriosclerosis?
Thickening and hardening of the arteries as a consequence of atherosclerosis
What is arteriolosclerosis?
Hardening and thickening of the arterioles, mainly affects the kidey. Little or no connection with atherosclerosis, linked to diabetes or sever hypertension
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What is Monckeburg’s disease?
Uncommon disease where there is calcification of the media of the large arteries
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What is an atheroma and what does it consist of?
Necrotic core of atherosclerotic plaque, consists of dead cells, debris and cholesterol crystals
What is an atherosclerotic plaque?
- Lesion of atherosclerosis containing:
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What are the proccesses involved in plaque formation?
1. Chronic endothelial insult
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- Lipid droplets, mainly from LDL’s, cross from damaged endothelium and accumulate in intima. Monocytes attracted
- Lipids oxidised and macrophages ingest them to become foam cells
- Crowds of foam cells cause endothelium to bulge and smooth muscle cells migrate into lesion from media and start to proliferate = fatty streak
- Plaque continues to grow as foam and smooth muscle cells proliferate. Muscle cells take up some lipid and foam secrete cytokines
- Smooth muscle cells lay on top of plaque beneath endothelium and reenforced by collagen and elastin to form fibrous cap
- As endothelium stretches over plaque gaps appear between cells and platelets adhere to gaps
- Cells in centre of plaque undergo necrosis and released cholesterol so cholesterol crystals
- Small blood vessels grow into plaque from adventitia and plaque can undergo calcification
What can cause chronic endothelial insult?
- Hyperlipidaemia
- Smoking
- Hypertension
- Haemodynamic factors
What are the macroscopic appearances of atherosclerosis?
1. Fatty streak: flat and no disturbance to blood. yellow and form in childhoold
2. Simple plaque: white/yellow and impinge on lumen
3. Complicated plaque: Thrombosis and haemorraghe into plaque
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What does atherosclerosis look like microscopically?
- Fatty streak: foam cells, extracellular lipid, smooth muscle cells (flat and yellow)
- Plaque: Fibrosis, necrosis, cholesterol clefts, distruption of elastic lamina, extension into media and ingrowth of vessels from adventitia, inflammatory cells (raised)
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Where are the most common sites of athersclerosis?
- Effects mainly seen in heart, brain, kidneys, legs or bowel
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How can plaques become complicated?
- Ulceration: fibrous cap eroded and plaque exposed to blood so thrombogenic
- Thrombosis on plaque: may occlude lumen
- Spasm at site of plaque: vasoconstrictors released from thrombi
- Embolisation
- Calcification: stiffening artery
- Haemmoraghe: break plaque open or occlude
- Aneurysm formation
- Rupture of atherosclerotic artery: weakend media mainly in cerebral arteries with hypertension
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Why might a atherosclerotic plaque lead to an aneurysm?
- Local dilatations due to elastic tissue destroyed by plaque which weakens walls
- May rupture or thrombus occur within them that embolises
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What conditions can plaques lead to ?
- Heart: MI, chronic ischemic heart disease, arrythmias, cardiac failure, sudden cardiac death
- Brain: TIA, cerebral infarction (stroke), multiinfarct dementia
- Kidneys: hypertension, renal failure
- Legs: peripheral vascular disease, gangrene
- Bowel: ischemic colitis, malabsorption, bowel infarction
ALL DUE TO NARROWING OF VESSELS OR EMBOLISMS FROM PLAQUE
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