Cholesterol and CHD

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Functions of Blood Cholesterol

Membrane structure and fluidity

Synthesising steriod hormones

Synthesising vitamin D

Producing bile

Waterproofing skin

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Cholesterol is insoluble in blood plasma so it is transported by lipoproteins, which are made in the liver.

The centre of a liporprotein contains cholesterol and other lipids (triglycerides and steroids). They are coated in a single phospholipid layer, with proteins to make it soluble.

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High Density Lipoproteins

More proteins, fewer lipids

Remove cholesterol from tissues and return it to the liver

HDL receptors on liver cells

Decrease blood cholesterol and fat deposists

Decrease rate of formation of atheromas (plaques)

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Low Density Lipoproteins

More lipids, fewer proteins

Deliver cholesterol to tissues from the liver

LDL receptors on tissue cells

Raise blood cholesterol and fat deposits

Increase rate of formation of atheromas (plaques)

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First Step

If the endothelial lining of an artery is damaged, LDLs tend to deposit fat and cholesterol in them.

This accumulates along with fatty acids, calcium salts and fibrous tissues, forming an atheromatous plaque.

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Second Step

Atherosclerosis is the stiffening and hardening of the artery walls caused by a build-up of plaque.

This leads to a bulge in the artery wall which narrows the lumen and restricts blood flow.

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Third Step

If oxygenated blood flow is restricted, the cardiac muscle may become deprived of oxygen and fatigued, causing angina which is severe chest pains.

The plaque deposits also roughen the lining of the artery which increases the risk of blood clots forming.

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Fourth Step

If the artery is almost completely blocked by atheromatous plaque and blood clots, a heart attack (myocardial infarction) may occur.

Cardiac muscle is starved of oxygen and cells rapidly die. This may be fatal.

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