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Atherosclerosis - Biology - AS Level
What is Atherosclerosis?
Atherosclerosis is a dangerous disease process that leads to coronary heart diseases and strokes.
Fatty deposits can either block an artery completely or increase the chance of an artery being blocked by a blood clot.
If a block occurs (from the atherosclerosis and a blood clot) in the heart, then a heart attack (myocardial infarction) will occur.
If a block occurs in the brain, it is called a stroke.
Heart attacks and strokes occur because when blood supply is restricted or denied from cells they die.
Atherosclerosis - Step 1 - Damage
The first step and so the cause of atherosclerosis is damage to the endothelium of an artery.
The endothelium is a very thin layer of cells that lines the inside of an artery and thus is quite vulnerable to damage from the high pressure blood flow that an artery (the blood vessel that carries blood away from the heart) has to deal with.
Damage to the endothelium can also occur from the toxins that are found in cigarette smoke and therefore it is said that smokers are more at risk from atherosclerosis (and so heart attacks and stroke) than other people.
Atherosclerosis - Part 2 - Inflammatory Response
After the endothelium has been damaged, an inflammatory response occurs.
- White blood cells leave the blood vessel and move into the artery wall.
- Chemicals accumulate on the white blood cells, particularly cholesterol.
- This deposit is called an atheroma (making up the 'athero' in 'atherosclerosis')
Atherosclerosis - Part 3 - Sclerosis
- Fibrous tissue and calcium salts add themselves to the atheroma formed.
- This creates a hard plaque (hard swelling of the aterial wall)
- As a result, elasticity of the artery is lost.
Atherosclerosis - Part 4 - Positive Feedback
- Since the plaques make the artery narrower (by taking up space in the lumen), blood pressure is raised.
- Higher blood pressure increases the chance of atherosclerosis and therefore as atherosclerosis increases, the chance of acquiring further atherosclerosis increases (positive feedback).