Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, cardiovascular and thoracic biology (CTB) module.
Lecture 7 on cell biology of the cardiovascular system: how cellular components of the cardiovascular system help maintain vascular homeostasis.
Homeostasis is a he...
Cell Biology of cardiovascular system
- vascular homeostasis maintained by constant adjustment of biochemical + physiological pathways
Structure of blood vessels
- 3 layers: intima, media, adventitia
=> veins: thinner + less muscularised than arteries
=> smaller vessels: less muscular medial layer (capillaries = only endothelial cells)
-
Ifibroblasts)
E
Ismooth muscle alls)
-
- intima = smooth & non-adhesive (for platelets + leukocytes) single-cell layer of endothelial cells
=> endothelial cells adhere tightly to each other => selective barrier
- endothelium: fractal geometry => large area in body (lung endothelium = 130m^2)
=> effective gases + nutrients exchange
- endothelial cells
=> “cobblestone” (pavés) morphology in small vessels
=> flatten out + elongate within flow direction in large vessels
=> minimise mechanical forces => minimise risk of vascular injury
- edges of cells overlap => increase junctional area + strengthen barrier function
, compliance: ability to
- media: vascular smooth muscle cells in collagen + elastin respond to increased BP
=> increase/ decrease V
scaffold for smooth muscle, vessel strength + compliance
- aorta: many layers of smooth muscle + abundance of collagen & elastin for arterial pressure
- pulmonary artery: fewer layers of smooth muscle + more elastin: changes in V without BP changes
=> vascular tone regulation (contraction/ relaxation: endothelium-dependent or independent)
- adventitia: collagen, elastin, other extracellular matrix interspersed with fibroblasts
- aorta: thick adventitia w/ more collagen => non-compliant
- pulmonary artery: thick adventitia w/ more elastin => compliant
=> produce structural extracellular matrix p regulating vascular compliance
Regulation of vascular tone
- maintenance of body homeostasis
=> ex: vasodilation helps body to lose heat/ vasoconstriction helps body to keep heat
- balance bw vasoconstrictors & vasorelaxants
Vasodilators Vasoconstrictors
NO
ET-1
PGI2
Angiotensin II
natriuretic peptides
Thromboxane
(ET-1)
- vasorelaxants/ vasodilators: Angiotensin II
=> Nitric Oxide (NO):
=> produced from L-arginine by eNOS (activated by shear stress, chemicals: brady. + acetyl...)
=> NO diffuses into smooth muscle => activate soluble guanylate cyclase => cGMP
=> also inhibits smooth muscle proliferation, inflammation, platelet adhesion
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