What is atherosclerosis?
Atherosclerosis is the narrowing of the lumen and hardening of the walls in the arteries, which occurs originally due to damage to the endothelial cells in the arteries. This can be as a result of high blood pressure (hypertension), which exerts more force on the artery walls, or from the chemicals in smoking causing the damage, for example.
As a result of the damaged endothelium, lipids will begin to accumulate and as a result of the body’s inflammatory response white blood cells (leukocytes) will be attracted to the damaged area and differentiate into macrophages, which engulf the lipid substances such as cholesterol. This creates plaque build up, also known as atherome, and the more the macrophages engulf the larger they become creating more plaque build and therefore further narrowing of the lumen. (This is why it is bad to have high cholesterol levels). Furthermore calcium salts and fibrous tissue can build up around the plaque, causing it to harden therefore reducing the elasticity of the artery wall.
The narrowed lumen will result in higher blood pressure as it is harder for the heart to pump the blood around the body. As a result of this there is a high chance of endothelial cells being damaged in other arteries and as a result a plaque build and therefore atherosclerosis will occur again.
Atherosclerosis is the narrowing of the lumen and hardening of the walls in the arteries, which occurs originally due to damage to the endothelial cells in the arteries. This can be as a result of high blood pressure (hypertension), which exerts more force on the artery walls, or from the chemicals in smoking causing the damage, for example.
As a result of the damaged endothelium, lipids will begin to accumulate and as a result of the body’s inflammatory response white blood cells (leukocytes) will be attracted to the damaged area and differentiate into macrophages, which engulf the lipid substances such as cholesterol. This creates plaque build up, also known as atherome, and the more the macrophages engulf the larger they become creating more plaque build and therefore further narrowing of the lumen. (This is why it is bad to have high cholesterol levels). Furthermore calcium salts and fibrous tissue can build up around the plaque, causing it to harden therefore reducing the elasticity of the artery wall.
The narrowed lumen will result in higher blood pressure as it is harder for the heart to pump the blood around the body. As a result of this there is a high chance of endothelial cells being damaged in other arteries and as a result a plaque build and therefore atherosclerosis will occur again.
What are the effects of atherosclerosis?
Aneurysms: Where the lumen of an artery is narrowed due to plaque build up, blood tends to build up behind the blockage and as a result more pressure is exerted on the artery wall, therefore weakening it. This artery wall could then split open and as result leading to mass internal bleeding which can be fatal.
Raised blood pressure: High blood pressure can damage the tiny blood vessels in the body. If the blood vessels supplying the retina are damaged for example, then the retinal cells can be starved of oxygen and therefore die causing blindness.
Heart disease
Stroke: A stroke occurs when there is an aneurysm in the capillaries supplying the brain or as a result of blood clot or atheroma in arteries supplying blood to the brain. If there is a blood clot in a major artery leading to the brain, for example the carotid artery, the effects of a stroke can result in death. If the clot is in a smaller artery leading to the brain the effects of a stroke will be less disastrous although may still cause dizziness, slurred speech or loss of vision.
Aneurysms: Where the lumen of an artery is narrowed due to plaque build up, blood tends to build up behind the blockage and as a result more pressure is exerted on the artery wall, therefore weakening it. This artery wall could then split open and as result leading to mass internal bleeding which can be fatal.
Raised blood pressure: High blood pressure can damage the tiny blood vessels in the body. If the blood vessels supplying the retina are damaged for example, then the retinal cells can be starved of oxygen and therefore die causing blindness.
Heart disease
- Angina: As a result of plaque build up in the coronary arteries blood flow to specific parts of the heart muscle may be reduced. Therefore less oxygen is supplied to the heart muscle forcing it to respire anaerobically and as a result giving strong chest pains. The signs of angina are first noticed during exercise when the heart muscle has a higher demand for oxygen and therefore blood. As the coronary artery becomes narrower the symptoms of angina become worse.
- Myocardial infarction: As a result of atherosclerosis the artery wall affected by plaque build up is hardened and therefore more prone to cracking. If the plaque is ruptured then the cholesterol released may trigger the platelets to create a blood clot. As the vessel is already blocked by plaque build up a clot can rapidly block the whole vessel, this is known as thrombosis. If the coronary artery is blocked then part of the heart muscle is permanently starved of oxygen causing it to die.
- Coronary heart disease: Where the Coronary artery is blocked with plaque and as a result angina or Myocardial infraction can occur.
Stroke: A stroke occurs when there is an aneurysm in the capillaries supplying the brain or as a result of blood clot or atheroma in arteries supplying blood to the brain. If there is a blood clot in a major artery leading to the brain, for example the carotid artery, the effects of a stroke can result in death. If the clot is in a smaller artery leading to the brain the effects of a stroke will be less disastrous although may still cause dizziness, slurred speech or loss of vision.
What factors affect the risks of atherosclerosis?
Non-modifiable factors
Modifiable factors
Non-modifiable factors
- Genes: Genetic tendencies, such as having arteries, which are more easily damaged, a tendency to develop hypertension and poor cholesterol metabolism can all affect the risks of atherosclerosis.
- Age: As you get older blood vessels will narrow and loose their elasticity making them more prone to atherosclerosis.
- Gender: Women under the age of 50 suffer from atherosclerosis significantly less than men do. This is as a result of high oestrogen levels, which reduces the build up of plaque, until menopause when oestrogen levels fall.
Modifiable factors
- Smoking: chemicals in cigarettes will damage the artery lining therefore creating a plaque build up, which can block the arteries.
- Exercise: Regular exercise lowers blood pressure, lowers blood cholesterol, reduces stress and prevents obesity and diabetes, all of which increase the likelihood of atherosclerosis.
- Prolonged stress: Stress causes the release of cytokines, which create an inflammatory response in blood vessels leading to the formation of plaque.
- Diet: Consuming foods with high levels of saturated fat increases the risk of atherosclerosis because they contain high levels of low-density lipoprotein cholesterol. If there is an excess of cholesterol for the cells to use, LDL will build up an be deposited in the arteries creating atheroma.