Atherosclerosis

[biomedicool]

Accumulation of fatty material in the artery walls resulting in a narrowing or blocking

• Affects mainly medium-large arteries
  
• Only occurs in arteries with high pressure
• Does not occur in veins unless exposed to systemic arterial pressures

Atheroma Formation 

• disease of the tunica intima but can impact on the tunica media
• accumulation of lipid rich material to for plaques

ONE

• Endothelial damage occurs allowing entry to LDLs (low-density lipoproteins) into the tunica intima
  

TWO

• Lipid taken up by macrophages in the intima
  
• Accumulates to form a visible white bulge - fatty streak
  

THREE

• Continued accumulation of lipids
  
• cytokines from macrophages stimulate proliferation of intima cells with features of myofibroblasts
  
• these secrete collagen - plaque starts to become fibrotic
  
• lesions are more raised and yellower
• as the lesion develops there is a pressure atrophy of the tunica media and the elastic lamina is disrupted

Four

• Increased collagen secretion forms a dense, fibrous cap (fibrolipid cap) which is hard and white
  
• this advanced plaque shows free lipid as well as the lipid in macrophages
  
• collagen build up also weakens the arterial wall
• endothelium is fragile and often ulcerates, allowing platelet aggregation and formation of a thrombus (clot) (thrombosis)