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atheroma
An atheroma is an accumulation of degenerative material in the tunica intima (inner layer) of artery walls. The material consists of (mostly) macrophage cells, or debris, containing lipids (cholesterol and fatty acids), calcium and a variable amount of fibrous connective tissue. The accumulated material forms a swelling in the artery wall, which may intrude into the channel of the artery, narrowing it and restricting blood flow. Atheroma occurs in atherosclerosis, which is one of the three subtypes of arteriosclerosis (which are atherosclerosis, Monckeberg's arteriosclerosis and arteriolosclerosis).〔http://www.mercksource.com〕
In the context of heart or artery matters, atheromata are commonly referred to as atheromatous plaques. It is an unhealthy condition, but is found in most humans.
Veins do not develop atheromata, unless surgically moved to function as an artery, as in bypass surgery. The accumulation (swelling) is always in the tunica intima, between the endothelium lining and the smooth muscle tunica media (middle layer) of the artery wall. While the early stages, based on gross appearance, have traditionally been termed fatty streaks by pathologists, they are not composed of fat cells, i.e. adipose cells, but of accumulations of white blood cells, especially macrophages, that have taken up oxidized low-density lipoprotein (LDL). After they accumulate large amounts of cytoplasmic membranes (with associated high cholesterol content) they are called foam cells. When foam cells die, their contents are released, which attracts more macrophages and creates an extracellular lipid core near the center to inner surface of each atherosclerotic plaque. Conversely, the outer, older portions of the plaque become more calcified, less metabolically active and more physically stiff over time.
==Signs and symptoms==
For most people, the first symptoms result from atheroma progression within the heart arteries, most commonly resulting in a heart attack and ensuing debility. However, the heart arteries, because (a) they are small (from about 5 mm down to microscopic), (b) they are hidden deep within the chest and (c) they never stop moving, have been a difficult target organ to track, especially clinically in individuals who are still asymptomatic. Additionally, all mass-applied clinical strategies focus on both (a) minimal cost and (b) the overall safety of the procedure. Therefore, existing diagnostic strategies for detecting atheroma and tracking response to treatment have been extremely limited. The methods most commonly relied upon, patient symptoms and cardiac stress testing, do not detect any symptoms of the problem until atheromatous disease is very advanced because arteries enlarge, not constrict in response to increasing atheroma.〔http://www.nejm.org/doi/full/10.1056/NEJM198705283162204〕 It is plaque ruptures, showing debris & clots which obstruct blood flow downstream, sometime also locally (as seen on angiograms), which reduce/stop blood flow. Yet these events occur suddenly & are not revealed in advance by either stress testing, stress tests or angiograms.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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