Atherogenesis Flashcards
What is atherogenesis?
- formation of fatty deposits in arteries
- progressive inflammation follows
What are some risk factors that are not able to be modified for atherogenesis?
- gender (male 10 years earlier)
- genetic abnormalities
- increasing age (MAIN RISK)
- family history
What are some risk factors that are modifiable for atherogenesis?
- smoking
- high cholesterol
- high blood pressure
- diabetes
What are the 3 main layers of the arterial walls? (inner to out layers)
- innermost = intima
- middle = media
- outermost = adventitia
What is the inner most layer of arterial walls composed of?
- endothelium
- squamous epithelial cells
What is the middle layer of arterial walls, called media composed of?
- smooth muscle
What is the outer most layer of arterial walls, called adventitia composed of?
- tough fibrous tissue
What does atherosclerosis mean?
- athero = greek for gluey/fatty yellow
- sclerosis = german for hardening
What are the 2 main parts of an atheromatous plaque?
1 - fibrous cap
2 - necrotic core
What is a fibrous cap?
- layer of fibrous tissue connective tissue
What layer of the arterial walls does the fibrous cap form in?
- below endothelium
Generally what cells are found within a fibrous cap?
- smooth muscle cells
- macrophages
- lymphocytes
What are the fibres that contribute towards the fibrous cap?
- elastin
- collagen
- proteoglycans
As fibrous cap formation is inflammation, what do arterial walls need to create to supply the fibrous cap with blood?
- neovascularisation
What is the necrotic core formed in atherosclerosis?
- forms inside the intima below fibrotic cap
- necrotic components under fibrous cap
What are the main components of the necrotic core that also contribute to stiffening of the arteries?
- cholesterol crystals
- Ca2+ salts
- foam cells (from macrophages)
In the lipid hypothesis, roughly when was LDL cholesterol linked with atherosclerosis?
- 1980s
What is the lipid oxidation hypothesis in atherosclerosis?
- free radicals modify LDL cholesterol
If free radicals have modified LDL cholesterol, what can that cause in the innate immune system?
- macrophages absorb LDL, but do not normally
- macrophages become foam cells and undergo necrosis
What was the main problem with the lipid oxidation hypothesis?
- did not account for non lipid risk factors
- age, genetics, smoking
What was the conclusion about the lipid oxidation hypothesis?
- contributes
- NOT primary cause
When looking at research into atherosclerosis, what is one important thing to keep in mind?
- evidence is based on pre-clinical models
What is the response to injury hypothesis?
- atherosclerosis in a chronic inflammatory process to endothelial injury
In order for fatty streaks to form and then go onto atherosclerosis, what is the first thing that must happen in the endothelium in the injury hypothesis?
- endothelial are damaged and injuryed
- endothelial dysfunction follows
Following the initial injury/dysfunction in endothelium in the response to injury hypothesis, what then accumulates at the site of injury/dysfunction?
- lipoproteins
In a similar manner to acute inflammation, once there is an initial injury/dysfunction to endothelium what migrates to the area as part of the response to injury hypothesis?
- leukocyte, specifically monocytes
- margination, adhesion and migration into intima
What is primary leukocyte (WBCs) involved in the early phase of the response to injury hypothesis?
- monocytes differentiate into macrophages
- lipids accumulate and macrophages phagocytose them
- macrophages become foam cells
- macrophages undergo necrosis and release contents