atheroma Flashcards
what is atheroma
accumulation of material in wall of large and medium arteries
changes that occur in hypertensive arteriosclerosis
Hypertrophy of media
Fibroelastic thickening of intima
Elastic lamina reduplication
Changes that occur in hypertensive arteriolosclerosis
Replacement of wall structures by amorphous hyaline material
Consequences of hypertensive vascular changes
Reduction of vessel lumen -> reduced flow ->
ischaemia in supplied tissue
Increased rigidy of vessel wall -> loss of elasticity and contractility -> unresponsive to normal vessel control agents eg vasodilators
Four stages of atheroma formation
Fatty streak
Lipid plaque
FIbrolipif plaque
Complicated atheroma
First step of atheroma formation
Blood lipids enter intima through damaged endothelium
Lipids are phagocytosed by macrophages in intima to make raised ‘fatty streak’
Second stage of atheroma formation
Some lipid is released by macrophages which forms lipid plaque
Macrophages secrete cytokines which stimulate my-fibroblasts to secrete collagen
Early damage to elastic lamina and media
third stage of atheroma formation
Collagen covers plaque surface (‘fibrolipid plaque’)
Media thins, with replacement of muscle fibres by collagen
Fourth stage of atheroma formation
Lipids in intimate become calcified. Surface of fibre-lipid plaque ulcerates
Thinning of media leads to weakness and inelasticity (complicated atheroma)
How do atheroma lead to plaque fissure formation
Blood seeps into atheromatous plaque and expands It OR
blood seeps into plaque and undergoes thrombosis
How can an atheroma lead to an aneurysm
Damage to media
because:
-Enlarging intimal atheroma plaque leads to atrophy of media
-Muscle and elastic fibres in media replaced by collagen
-Collagen strong but neither contractile nor capable of elastic recoil
-WIth each systolic pulse, wall of artery stretches and thins, particularly when BP is high
-Most common in abdo aorta
