6) Atheroma

Question 1

Define atheroma.

Answer 1

The accumulation of intracellular and extracellular lipid in the intima and media of large and medium sized arteries.

Question 2

Define atherosclerosis.

Answer 2

The thickening and hardening of arterial walls as a consequence of atheroma.

Question 3

Define arteriosclerosis.

Answer 3

The thickening of the walls of arteries and arterioles, usually as a result of hypertension or diabetes mellitus.

Question 4

Describe the macroscopic appearance of atheroma.

Answer 4

• Fatty streak (yellow, slightly raised lipid deposits in the intima)
• Simple plaque (raised yellow/white with an irregular outline)

-Complicated Plaque:
\+ Thrombosis
\+ Haemorrhage into plaque
\+ Calcification
\+ Aneurysm formation

Question 5

Describe the microscopic appearance of atheroma.

Answer 5

-Early:
+ Proliferation of smooth muscle cells
+ Accumulation of foam cells
+ Extracellular lipid

-Late:
+ Fibrosis/necrosis
+ Cholesterol clefts (cholesterol deposition UNDER the tissue i.e. not the plaque)
+ There can be inflammatory cells

Question 6

Discuss the unifying hypothesis of Atherogenesis

Answer 6

-There is endothelial injury due to a variety of factors e.g. raised LDL, toxins

-The endothelial injury causes exposure of the sub endothelium (specifically collagen) which then leads to:
+Platelet adhesion andPDGF release
+Smooth muscle proliferation and migration
+Insudation of lipid, LDL oxidation, uptake of lipid by SMC and macrophages
+Migration of monocytes into intima

• Stimulated SMC produce matrix material
• Foam cells (macrophages with lipid in them) secrete cytokines causing further smooth muscle stimulation and the recruitment of other inflammatory cells