vascular endothelium Flashcards
what % of all endothelial cells reside within vasculature
98%
what is the basic structure of blood vessels
3 layers
tunica adventitia: vasa vasorum, nerves
tunica media: smooth muscle cells
tunica intima: endothelium, basement membrane, lamina propria and internal elastic membrane
what are capillaries and venules
endothelium supported by mural cells (pericytes) and basement membrane
what takes place in the capillaries
where exchanges of nutrients and oxygen between blood and tissues occur
what is another function of microvascular endothelium
promotes tissue haemostasis
damage to endothelium can cause organ dysfunction
what is required for maintenance of tissue homeostasis and organ regeneration
angiocrine factors in microvascular endothelium
why does dysfunctional endothelium contribute to disease more than any other organ
contribute to components of: ischaemia chronic inflammatory diseases cancer diabetes
basic function of endothelium
acts as vital barrier separating blood from tissues
very extensive surface area
endothelial cells are very flat 1-2ym thick
formed by monolayer of endothelial cells
cells regulate essential functions of blood vessels
what are the multiple functions of blood vessels and tissues that endothelium controls
tissue homeostasis and regeneration permeability vascular tone angiogenesis inflammation haemostasis and thrombosis
what is meant by endothelial cells are hetergenous
their function and phenotype depends on their location
what happens in resting endothelium
haemostasis
anti inflammatory, anti thrombotic, anti proliferative is balanced with pro inflammatory, pro thrombotic, pro angiogenic
what causes endothelium to be activated
risk factors:
inflammation - proinflammatory cytokines hypercholesterolaemia sex hormonal imbalance ageing mechanical stress viruses smoking oxLDL high bp high glucose
what does activated endothelium initially cause over time
thrombosis senescence - stress permeability leukocyte recruitment ALL these factors lead to ATHEROSCLEROSIS
how does fatty-streak formation occur in atherosclerosis
smooth muscle migration foam cell formation t cell activation adherence and aggregation of platelets adherence and entry of leukocytes
how is advanced complicated lesion of atherosclerosis formed
macrophage accumulation
formation of necrotic core
fibrous cap formation
angiogenesis
where do leukocytes gets stuck after endothelial activation
in sub endothelial space
they then differentiate into macrophages and become foam cells
what does increased membrane permeability cause
leakage of plasma proteins through junctions into subendothelial space
why do atherosclerotic plaques occur preferentially at birfurcations and curvatures of vascular tree
flow patterns and haemodynamic forces are not uniform in vascular system and irregular distribution of low wall sheer stress
what does laminar blood flow promote
anti thrombotic, anti inflammatory factors
endothelial survival
inhibition of smooth muscle cell proliferation
nitric oxide production
what does disturbed blood flow promote
thrombosis, inflammation (leukocyte adhesion)
endothelial apoptosis
smc proliferation
loss of nitric oxide production
what are some of the protective effects nitric oxide has on vascular endothelium
reduces oxidation of ldl cholesterol dilates blood vessels reduces platelet activation inhibits monocyte adhesion reduces proliferation of smc in vessel wall reduces release of superoxide radical
what is angiogenesis
formation of new blood vessels by sprouting from existing vessels
what is angiogenesis essential for
embryonic development
wound healing
menstrual cycle
how does angiogenesis lead to atherosclerosis
promotes plaque growth
