Atherosclerosis (Session 6) Flashcards
What vasculature does atherosclerosis affect and what does it not affect?
- Affects arteries
- Does not affect veins or capillaries
What is the most common stage of life for atherosclerosis to be seen?
generally seen in middle to later life
What does atherosclerosis result in? (3)
- Stenosis of the arterial lumen.
- It can result in myocardial infarction and stroke
and is therefore the biggest killer in the Western world.
Flow through a stenosed tube or artery is not significantly affected until…
Until the lumen is reduced by 70-80%
What occurs to the tissue if less than 70-80% of the lumen is reduced?
Give an example
- The functional reserve of the affected tissue is reduced,
e.g., in moderate coronary artery atherosclerosis the heart may not get enough blood during exercise.
Where does atherosclerosis develop?
n patches of the intima often where flow is disturbed, e.g., around the opening of a branch.
Describe the key event that occurs in atherosclerosis (3)
- A focal accumulation of lipid and cells beneath the endothelium which forms a raised flat plaque.
- The plaque is usually about 1-2mm thick.
- This doesn’t sound very impressive but it can be a major obstacle to flow in arteries with a lumen of approximately 3 mm, such as coronary arteries.
How long does the process of plaque formation take?
Many years
Describe the arteries in which atherosclerosis occurs in
In elastic arteries (such as aorta, carotid and iliac arteries) and large and medium sized muscular arteries (such as coronary and popliteal arteries)
Which aorta is atherosclerosis commoner in? As opposed to what?
It is commoner in the abdominal rather than the thoracic aorta.
1) Define ARTERIOsclerosis
2) What happens in this condition
3) Which 3 diseases does it include?
1) Hardening of the arteries.
2) Walls of arteries are thickened and lose their elasticity.
3) * Atherosclerosis
* Arteriolosclerosis
* Monkeberg’s disease
Describe atherosclerosis
- a disease of large and medium sized arteries that begins in the intima.
- Plaques are formed in the arterial wall and these are filled with atheroma (a necrotic gruel- like material (athere is Greek for porridge)).
- The plaques often calcify.
Describe Arteriolosclerosis
- Hardening of the arterioles.
- This disease affects arterioles throughout the body but especially those of the kidney.
- It has little or no connection with atherosclerosis and usually occurs secondary to severe hypertension or in diabetes mellitus.
Describe Monkeberg’s disease
an uncommon disease where there is calcification of the media of large arteries.
What is an atheroma?
What does it consist of? (3)
The necrotic core of the atherosclerotic plaque.
It consists of dead cells, debris and cholesterol crystals.
1) What is the basic leison of atherosclerosis?
2) Name and describe the 3basic components that it has
1) The plaque
2) The plaque has three basic components:
- Cells – macrophages, leucocytes, smooth muscle cells,
- Intra- and extracellular lipid,
- Extracellular matrix – collagen, elastin, proteoglycans.
Describe step 1 of plaque formation
- Chronic endothelial insult from conditions such as hyperlipidaemia, hypertension, smoking or from haemodynamic factors result in endothelial dysfunction.
Describe step 2 of plaque formation
- Lipid droplets, mainly from low density lipoproteins (LDLs), and monocytes cross the endothelium and accumulate in the intima. The lipids become oxidised and the macrophages ingest the lipid. When they do so their cytoplasm appears bubbly microscopically and they are called foam cells.
Describe step 3 of plaque formation
- The crowded foam cells cause the endothelium to bulge. Smooth muscle cells migrate into the lesion from the media and start to proliferate. The lesion at this stage is called a fatty streak.
Describe step 4 of plaque formation
- The plaque grows as the number of foam cells and smooth muscle cells increases. Some smooth muscle cells will also take up lipid and appear foamy. Some smooth muscle cells will lie over the plaque but beneath the endothelium forming a ‘roof’. This roof is reinforced by collagen, elastin and other matrix proteins and the result is a fibrous cap. As the endothelium stretches over the plaque gaps appear between the endothelial cells. Platelets adhere to the gaps.
Describe step 5 of plaque formation
- Cells in the centre of the plaque die and necrosis develops. The dead cells release cholesterol and cholesterol crystals appear in the plaque (these are removed during tissue processing for microscopy leaving behind linear holes in the tissue section = cholesterol clefts). Small blood vessels grow into the plaque from the adventitia and the plaque may undergo calcification.
Summarise all the steps of plaque formation
- Chronic endothelial insult from conditions such as hyperlipidaemia, hypertension, smoking or from haemodynamic factors result in endothelial dysfunction.
- Lipid droplets, mainly from low density lipoproteins (LDLs), and monocytes cross the endothelium and accumulate in the intima. The lipids become oxidised and the macrophages ingest the lipid. When they do so their cytoplasm appears bubbly microscopically and they are called foam cells.
- The crowded foam cells cause the endothelium to bulge. Smooth muscle cells migrate into the lesion from the media and start to proliferate. The lesion at this stage is called a fatty streak.
- The plaque grows as the number of foam cells and smooth muscle cells increases. Some smooth muscle cells will also take up lipid and appear foamy. Some smooth muscle cells will lie over the plaque but beneath the endothelium forming a ‘roof’. This roof is reinforced by collagen, elastin and other matrix proteins and the result is a fibrous cap. As the endothelium stretches over the plaque gaps appear between the endothelial cells. Platelets adhere to the gaps.
- Cells in the centre of the plaque die and necrosis develops. The dead cells release cholesterol and cholesterol crystals appear in the plaque (these are removed during tissue processing for microscopy leaving behind linear holes in the tissue section = cholesterol clefts). Small blood vessels grow into the plaque from the adventitia and the plaque may undergo calcification.
1) What is the earliest leison in atherosclerosis?
2) Describe the appearance of the fatty streak
3) What do fatty streaks not do?
4) When do fatty streaks occur?
5) Describe the microscopic appearance of fatty streaks
The fatty streak
1) As fatty streaks grow, what do they become?
2) Describe the appearance of fatty streaks
3) Describe the microscopic appearance of fatty streaks
