Atherosclerosis (Edexcel International A Level Biology)

• There are a number of diseases of the heart, or cardiovascular diseases, that can affect blood vessels in different ways
• Atherosclerosis, also known as hardening of the arteries, is caused primarily by damage to the delicate endothelium of an artery followed by an inflammatory response
  • It is a progressive disease, meaning that it can worsen over time
• In a healthy artery the endothelium is smooth and unbroken to reduce friction between blood and the inside if the artery
• The steps involved in atherosclerosis are
  • Damage, e.g. by high blood pressure, is caused to the endothelium
    • Damage can also occur as a result of high levels of certain types of cholesterol, smoking, diabetes, obesity, and old age
  • An inflammatory response occurs and white blood cells, such as macrophages, accumulate in the damaged area
  • Lipids and cholesterol clump together with the macrophages under the endothelium and form fatty streaks
    • This is one of the first signs of atherosclerosis
  • Platelets can also add to the fatty deposit 
    • Platelets are fragments of red blood cells involved in the blood clotting process
  • The collection of cholesterol, lipids, macrophages and platelets accumulate under the endothelium 
    • The structure forms a plaque known as an atheroma 
  • The atheroma narrows the lumen of the artery, reducing and restricting blood flow and thereby raising blood pressure
  • Over time the plaque can calcify and harden, reducing elasticity of the artery wall and further increasing blood pressure

Atherosclerosis is the process by which atheroma plaques form in the endothelium of arteries