The Circulatory System

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  • Created by: Pope1912
  • Created on: 18-03-15 12:45

The Heart

 

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Cardiovascular Disease

Most cardiovascular disease starts with an atheroma formation. 

The endothelium (inner layer of the artery) is usually smooth and unbroken. 

When damage to the endothelium occurs, mainly due to high blood pressure, white blood cells and lipids from the blood clump together under the lining to form fatty streaks.

Over time more white blood cells, lipids and connective tissue build up and harden to form a fiberous plaque called an atheroma. 

This plaque partially blocks the lumen, restricting blood flow and therefore increasing the pressure.

Atheromas increase the risk of aneurysm and thrombosis. 

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Aneurysm

An aneurysm is a balloon-like swelling of the artery. 

Atheroma plaques damage and weaken the arteries. They also narrow the lumen increasing blood pressure. 

When blood travels through a weakened artery at high pressure, it may push the iner layers of the artery through the outer elastic layer. This forms a balloon like swelling called an aneurysm. 

The aneurysm may burst causing a haemorrhage.

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Thrombosis

Thrombosis - the formation of a blood clot.

An atheroma is a plaque that can rupture the endothelium lining of an artery.

This damages the artery wall and leaves a rough surface.

Platelets and fibrin accumulate at the site of the damge and form a blood clot.

,This clot can cause complete blockage of the artery or dislodge and block a blood vessel elsewhere in the body.

Debris from the rupture can cause another blood clot to form further down the artery.

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Myocardial Infarction

The heart muscle is supplied with oxygen from the coronary arteries. 

The blood contains the oxygen required for the heart muscle to carry out respiration.

If a coronary artery bacomes completely blocked an area of the heart muscle will be completely cut off recieving no blood and therefore no oxygen.

This causes myocardial infarction.

This can  cause damage to the heart muscle as well as death.

Symptoms include chest pain, shortness of breath and sweating. 

If large areas of the heart are effected then it can cause heart failure which is potentially fatal. 

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Risk Factors of CHD

1) High blood chlesterol and poor diet.

Cholesterol is one of the main constituents of the fatty deposits that form atheromas. A diet that is high in staurated fat will increase blood cholsterol.

High levels of salt also increase blood pressure.

2) Smoking.

Both carbon monoxide and nicotine increase the risk of cardiovascular disease.

Carbon monoxide combines with haemoglobin and reduces the amount of oxygen transported in the blood and therefore restricts the tissues.

If the heart does not recieve enough oxygen it can result in mycardial infarction.

Smoking decreases the amount of antioxidants in the blood. These antioxidants are important for protecting cells from damage. This increases the risk of damage in the coronary artery walls which can lead to atheromas.

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Risk Factors of CHD

3) High blood pressure.

This increases the irsk of damage to the artery walls.

Damaged walls have an increased risk of atheroma formation which therefore causes a further increase in blood pressure.

Blood clots can form and block the blood flow resulting in myocardial infarction.

Weight, alcohol comsumption, not exercising etc all increase blood pressure.

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