Changes

==Epidemiology==

==Epidemiology==

Atherosclerosis generally does not affect individuals below the age of 35. While cholesterol may be transiently deposited, it is quickly removed. Above the age of 35, reports of prevalence are highly variable. Some studies report ranges of between 2.5% and 31.7% in asymptomatic individuals<ref>[http://eurheartj.oxfordjournals.org/content/21/1/13.full.pdf Prevalence of coronary atherosclerosis in asymptomatic population]. ''European Heart Journal, 21, 13-14''</ref>.

Atherosclerosis generally does not affect individuals below the age of 35. While cholesterol may be transiently deposited, it is quickly removed. Above the age of 35, reports of prevalence are highly variable. Some studies report ranges of between 2.5% and 31.7% in asymptomatic individuals.<ref>[http://eurheartj.oxfordjournals.org/content/21/1/13.full.pdf Prevalence of coronary atherosclerosis in asymptomatic population]. ''European Heart Journal, 21, 13-14''</ref>

==Risk Factors==

==Risk Factors==

Cholesterol circulates in the bloodstream contained in molecules called lipoproteins. The two most common forms are high-density lipoproteins ("good cholesterol", which reduces atherosclerosis) and low-density lipoproteins ("bad cholesterol", which increases atherosclerosis).

Cholesterol circulates in the bloodstream contained in molecules called lipoproteins. The two most common forms are high-density lipoproteins ("good cholesterol", which reduces atherosclerosis) and low-density lipoproteins ("bad cholesterol", which increases atherosclerosis).

The wall of an artery is made of up three layers - the innermost ''tunica intima'', the muscular ''tunica media'', and the outer ''tunica adventitia''. Atherosclerosis affects the inner two layers. It is initiated by injury to the wall of an artery. In most cases, this is due to [[hypertension|high blood pressure]]. This increases the permeability of the tunica intima, allowing the passage of lipoproteins and white blood cells called [[macrophage|macrophages]] to the space between the tunica intima and media. Macrophages are responsible for engulfing debris through the process of phagocytosis, which allows its removal from the body. When they phagocytose lipoproteins, they trap the cholesterol in the artery wall, and become ''foam cells''.

The wall of an artery is made of up three layers - the innermost ''tunica intima'', the muscular ''tunica media'', and the outer ''tunica adventitia''. Atherosclerosis affects the inner two layers. It is initiated by injury to the wall of an artery. In most cases, this is due to [[hypertension|high blood pressure]]. This increases the permeability of the tunica intima, allowing the passage of lipoproteins and white blood cells called [[macrophage]]s to the space between the tunica intima and media. Macrophages are responsible for engulfing debris through the process of phagocytosis, which allows its removal from the body. When they phagocytose lipoproteins, they trap the cholesterol in the artery wall, and become ''foam cells''.

The macrophages release chemicals known as cytokines, which cause an inflammatory response. This results in the migration of smooth muscle cells, or myofibroblast, which lays a fibrous outer shell around the foam cells. The foams cells eventually die, resulting in the trapping of cholesterol and cellular debris inside the shell. The shell and its lipid core is known as a plaque, or atheroma. Occasionally cholesterol may crystallise within the plaque, forming cholesterol clefts.

The macrophages release chemicals known as cytokines, which cause an inflammatory response. This results in the migration of smooth muscle cells, or myofibroblast, which lays a fibrous outer shell around the foam cells. The foams cells eventually die, resulting in the trapping of cholesterol and cellular debris inside the shell. The shell and its lipid core is known as a plaque, or atheroma. Occasionally cholesterol may crystallise within the plaque, forming cholesterol clefts.

Individuals with advanced atherosclerosis may be given treatment to prevent the secondary complications of the disease. A common example is the use of Aspirin to reduce the likelihood of a coronary thrombus forming in the event of plaque erosion/rupture.

Individuals with advanced atherosclerosis may be given treatment to prevent the secondary complications of the disease. A common example is the use of Aspirin to reduce the likelihood of a coronary thrombus forming in the event of plaque erosion/rupture.

==See Also==

==See also==

*[[Heart disease]]

*[[Heart disease]]

*[[Cholesterol]]

*[[Cholesterol]]