What is atherosclerosis?

What is atherosclerosis?

In this disease, the wall of arteries become hard and thick. Atherosclerosis is also a type of arteriosclerosis that is disorder related to larger arteries. It occurs mostly due to aortic aneurysm , coronary artery disease and arterial disease of lower extremities. It leads to cerebrovascular disease. It is an important topic related to biology class 12.

The wall of artery consists of three main layers. These are -

1.Intima - The lumen of arteries is lined with intima which consists of single layer of endothelial cells.

2.Media - It is made up of a single layer of cells i.e the smooth muscle cells. These may be arranged in a single layer or multiple lamellae.

3.Adventitia - The outermost layer of the artery is known as adventitia.

A normal arterial wall consists mainly of lipids i.e phospholipid (particularly sphingomyelin) and cholesterol ester. In humans due to increase in age, thickness of intima is increased. A progressive increase in lipid content increases the rigidity of vessels.

What are the non-atheromatous forms of arteriosclerosis?

Atherosclerosis mainly includes the intimal layer and most commonly takes place in abdominal aorta and its lower extremities and large renal branches, the cerebral vasculature and coronary arteries. It may also accompany or accelerate the other kinds of arteriosclerosis. focal calcification and arteriosclerosis.

What is focal calcification?

It is also known as Monckeberg's sclerosis. It is mostly found in upper extremities, lower extremities and the arterial supply of genital tracts in both sexes. It leads to the hardening of arteries and the arteries become tortuous and hard.

What is arteriosclerosis?

In this disease, the arteries become thick due to deposition and thickening. It affects the intima and media of arteries and arterioles related to pancreas, spleen, adrenal and kidneys. It causes degenerative and hyaline changes. It is associated invariably with hypertension. In this case the wall of arteries become thick and rigid due to the precipitation of calcium salts with cholesterol that leads to the formation of plaques or calcification of already formed plaques. It refers to hardening of arteries. The artery that is affected loses its property of distension and the wall of the artery may rupture. There may occur the clotting of blood in the ruptured artery that may block the supply of blood. It occurs in the coronary artery and may lead to heart attack.

What is atherosclerosis?

It is the most important among the degenerative diseases related to arteries . It occurs due to deposition of variable combination of complex carbohydrates, lipids, fibrous tissue, blood and blood products (mainly cholesterol) and calcium in the intima or inner lining of the arteries leading to the narrowing of arteries. Arterioles remain unaffected. Coronary atherosclerosis in invariably related to aortic atherosclerosis.

What are the main kinds of lesions of atherosclerosis?

Lesions of atherosclerosis are of three kinds -

1.Fatty Streaks - It consists of intracellular deposition of lipids within the smooth muscles and intima. These fatty streaks are thin and short. They are in the form of slightly raised yellow coloured lines that are lies longitudinally along the inner surface of the arteries.

2.Plaques - They are also known as atherosclerotic or atheromatous plaques. They are nearly about 1 CM in diameter. They are focal, circumscribed and raised type of lesions. They comprise of different amounts of lipid and fibrous tissue.

3.Complicated lesions - The proliferation of small muscles and fibres lead to the growth of plaques.Plaques provide a rough surface to blood platelets that is the cause of release of platelet derived growth factor (PDGF) that causes the proliferation of smooth muscles. The lumen of the arteries decrease because of the growth of these plaques leading to the reduced supply of blood . Plaque formation in coronary artery leads to reduced or stopping the blood supply to the heart causing heart attack or stroke.

Which are the four processes that complicate the lesions?

These are the four processes that lead to the complication of lesions -

1.Due to the loss of endothelium, the surface ulcerates exposing the fatty acid contents to the blood stream.

2.Deposition of fibrin causes thrombosis on the surface of the plaque.

3.free blood may occur in plaque.

4.calcification may take place.

Arterial thrombus is almost always formed at the site of atheromatous plaque. An increased tendency to thrombosis is one of the primary fault responsible for atherosclerosis.

Which are the risk factors that lead to atherosclerosis?

Risk factors are those habits or conditions that are present in individuals who develop atherosclerosis more frequently than other individuals.

These are -

1.Hypertension

2.Hypercholesterolemia

3.Cigarette smoking

By treating hypertension and quitting cigarette smoking may reverse the risk of atherosclerosis while genetic factors and age are considered to be irreversible factors.

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