Atherosclerosis is a broad term used to explain many diseases related to blood vessels such as heart diseases. It affects 45% of all European and American population while it has began to affect significant numbers in the developing world. Therefore this is a big issue as this is the number one killer everywhere in the world.

Atherosclerosis is caused by the "hardening of the arteries". Arteries are blood vessels that carry oxygenated blood away from the heart to other organs. It affects mainly medium to large sized arteries, such as the aorta (The aorta is the largest artery in the body that starts from the heart and branches out to distribute oxygenated blood to all parts of the body). If it affects the coronary artery that supplies blood to the heart, it is called a coronary heart disease resulting in a heart attack.

There are numerous of risk factors for atherosclerosis leading to chronic inflammation within the walls of the arteries. These include, high blood pressure, oxidative damage, viral infections, advancing age, diabetes, smoking, lack of exercise, stress and increased intake of fat.

The hardening of the arteries is due to the build up of "atheroma" or plaque/fat within the arterial walls-the hallmarks of atherosclerosis. The process of the building up of the atheroma is a process called "atherogenesis". This process is mainly due to the penetration of monocytes (white blood cells) in the outer most layer of the arterial wall due to damage caused by the risk factors mentioned above. Although this observable fact is not fully understood, it is thought that it is a defensive mechanism to remove cholesterol by monocytes.

As the monocytes enter the artery wall it is transformed into macrophages (bacteria engulfing cells), a process called "differentiation". This is the initiation of the sluggish process of atherogenesis. As monocyte differentiates it expresses or forms receptors on its cell surface called "scavenger receptors". They are responsible for attacking bacteria and destroying it. In this case the receptors mistakenly surround and uptake cholesterol. This cholesterol present in the blood (the blood flow) can sometimes be modified specially by the free radicals in cigarette smoke making it more easily recognisable to these receptors.

Once the scavenger receptors swallow up cholesterol they can accumulate inside it forming something called a "foam cell". When subsequently large numbers of macrophages have accumulated cholesterol it is called a cholesterol filled "plaque" as explained by doctors. This plaque will progress and form a more dense plaque and form a lesion leading to a blockade of the blood flow. This ultimately if unchecked will lead to clinical complications due to the rupture of the lesion. The most frequent clinical problems of atherosclerosis include heart attacks and stroke due to reduced blood flow to the heart and brain respectively.

High blood pressure

High blood cholesterol

Diabetes

Smoking

Being overweight

Being physically inactive

Having a family history of early heart disease

Age

Why we age and Paradox of ageing.