Session 6: Atherosclerosis Flashcards
Define arteriosclerosis.
Hardening of arteries. Walls of arteries are thickened and lose their elasticity.
Arteriosclerosis includes three diseases. Which?
Atherosclerosis Arteriolosclerosis Monkeberg’s Disease
Define atherosclerosis.
Disease of large and medium sized arteries that begins in the tunica intima. Plaques are formed in the arterial wall and fill with atheroma. It’s the accumulation of intracellular and extracellular lipid in the intima and media of large and medium sized arteries.
Define arteriolosclerosis. Common cause of arteriolosclerosis.
Hardening of arterioles. It has little or no connection with atherosclerosis and usually occurs secondary to severe hypertension or in diabetes mellitus.
Which arterioles in the body does arteriolosclerosis affect in particular?
The kidneys.
What is Monkeberg’s disease?
Uncommon disease where there is calcification of the media of large arteries.
Define atheroma. What does it consist of?
The necrotic core of the atherosclerotic plaque. Consists of dead cells, debris and cholesterol crystals.
What are the three basic components of the atherosclerotic plaque?
Cells like macrophages, leucocytes, smooth muscle cells Intra and extracellular lipid Extracellular matrix like collagen, elastin and proteoglycans.
The formation of the atherosclerotic plaque can be divided five stages. Describe stage 1.
There’s chronic endothelial damage from conditions such as hyperlipidaemia, hypertension, smoking or from haemodynamic factors. This leads to endothelial dysfunction.
Describe stage 2 of atherosclerotic plaque formation.
Lipid droplets mainly from LDLs and monocytes cross endothelium to accumulate in tunica intima. Lipids become oxidised and macrophages ingest the lipid due to the oxidation. This turns the macrophages into foam cells as their cytoplasm now appears bubbly under a microscope.
Describe stage 3 of atherosclerotic plaque formation.
Accumulation of foam cells creates a bulge in the endothelium. Smooth muscle cells migrate into the lesion from the media and start to proliferate. This is now called a fatty streak.
Describe stage 4 of atherosclerotic plaque formation.
Plaque grows due to more accumulation of foam cells and smooth muscle. Some smooth muscle cells will also take up lipid and become foamy. Some smooth muscle cells will lie over the plaque but beneath the endothelium to form a roof over the plaque. The roof that has now formed is then reinforced by collagen, elastin and other matrix proteins to form what is called a fibrous cap. The endothelium stretches over the plaque, this causes gaps to appear between the endothelial cells and platelets will adhere.
Describe stage 5 of atherosclerotic plaque formation.
Cells in the centre of the plaque are walled off and will start to die and necrosis develops. Deads cells release cholesterol and cholesterol crystals appear in the plaque. Small blood vessels can grow into the plaque from the adventitia and the plaque may undergo calcification.
Describe the morphological appearance of atherosclerosis.
(Microscopically)
Earliest lesions are called fatty streak. Flat and cause no disturbance in blood flow.
They consist of foam cells + smooth muscle cells and some extracellular lipid so this is what you would find under the microscope.
As it grows the fatty streak will become a plaque with a yellow to white appearance. Under the microscope you would see fibrosis, necrosis, cholesterol clefts, disruption of the internal elastic lamina, extension into the media and ingrowth of small vessels from the adventitia.
What are cholesterol clefts?
The remains of what’s left when cholesterol crystals are removed during tissue processing. They appear as linear holes.
