Vascular endothelium Flashcards
Describe the 3 layers of all blood vessels (except capillaries and venules).
3 layers:
- Tunica adventitia
- Tunica media
- Tunica intima
Where does Non fenestrated vascular endothelium exist?
muscle, lungs, skin, BBB
Where does fenestrated endothelium exist?
kidney glomerulus, GI tract
Where does discontinuous endothelium exist?
In the liver and marrow sinus
What is it called when 2 cells come together to form a junction and stop each other from growing
Contact inhibition
What does contact inhibition allow the formation of?
A flat monolayer
What pathways are on when the endothelium is resting? (3)
- Anti-inflammatory
- Anti-thrombotic
- Anti-proliferative
What pathways are switched on when the endothelium is activated? (3)
- Pro-inflammatory
- Pro-thrombotic
- Pro-angiogenic
- What factors can trigger chronic activation of endothelium? (7)
- Viruses
- Smoking
- Mechanical stress
- Inflammation
- OxLDL
- High bp
- High glucose
What does chronic endothelium activation cause? (4)
- Thrombosis
- Senescence- ageing of endothelial cells
- Leukocyte recruitment
- Permeability
What is a leukocyte?
White blood cell
After the endothelium is injured and activated, describe the steps leading to a lesion of atherosclerosis.
-Injury increases endothelial permeability
-Allows leukocyte infiltration, accumulating in the subendothelial space
-They then phagocytose lipids to create foam cells….
What causes leukocyte recruitment.
Inflammatory agents activating the endothelium .
Where does leukocyte recruitment usually occur?
In the post capillary venules during inflammation.
Where does leukocyte recruitment occur in atherosclerosis?
-Leukocytes adhere to activated endothelium of LARGE ARTERIES and get stuck in the subendothelial space
-Monocytes migrate into sub endothelial space, differentiate into macrophages and become foam cells.
At what parts of the vascular system are atherosclerotic plaques more likely to occur?
Bifurcations and curvatures of the vascular tree
Which blood vessels in particular is plaques likely to form?
- Aortic bifurcation (at the arch)
- Coronary artery bifurcation
- Carotid artery bifurcation
- Iliac arteries
- Femoral arteries
- In abdomen
How does blood flow differ between straight parts and in branches/curvatures of the vasculature?
-In straight parts of the arterial tree, blood flow is LAMINAR and wall shear stress is high and directional.
-In branches and curvatures, blood flow is disturbed with nonuniform and irregular distribution of low wall shear stress
What is the effect of laminar blood flow on the endothelium? (4)
- Anti-thrombotic (e.g. thrombomodulin) and anti-inflammatory factors
- Endothelial survival
- Inhibition of SMC (vascular smooth cell) proliferation
- Nitric oxide production
What is the effect of disturbed blood flow on the endothelium? (4)
- Promotes thrombosis and inflammation (leukocyte adhesion)
- Endothelial apoptosis
- SMC proliferation
- Loss of NO production
What is the importance of NO in the cardiovascular system? (6)
It’s essential for the health of the system:
- Reduces oxidation of LDL cholesterol (major component in plaque)
- Dilates blood vessels
- Reduces platelet activation
- Reduces release of superoxide radicals
- Reduces proliferation of SMC in the vessel wall
- Inhibits monocyte adhesion
