cardiovascular system - blood vessels Flashcards
arteries
transport blood AWAY from the HEART, therefore under high pressure
veins
transport blood TO the HEART
capillaries
exchange transported material with interstitial fluid (ISF) - between vessels and cells
blood vol. distribution
-arteries: 13%
-arterioles + capillaries: 7%
-heart: 7%
-pulmonary circulation: 9%
-veins, venules + venous sinuses: 64%
blood vessel walls
-adventitia
-media
-intima
tunica adventitia structure
-connective tissue
-fibroblasts and fibrous elements
tunica media structure
-circumferentially arranged smooth muscle cells
-elastic fibres
-collagen fibres
tunica intima structure
-endothelial cells
-sub-endothelium (collagen + smooth muscle)
-elastic fibres
arteries
-elastic
-muscular
-terminal
-arterioles
elastic arteries
-largest arteries (closest to heart)
-tunica media contains MORE elastic tissue and little smooth muscle
-absorb pressure wave generated by heart as it beats, converting pulsative flow into smoother continuous flow
muscular arteries
-contain smooth muscle but less elastic fibres
end(or terminal)-arteries (resistance vessels)
-diameter 100-150µm
-sole source of blood to a tissue
-when an end-artery is blocked the tissues it supplies die as there is no alternative blood supply
arterioles (resistance vessels)
-diameter 10-100µm
-tunica media consists almost entirely of smooth muscle
-control release of blood to capillaries
blood pressure (120-20 (mm Hg))
aorta + other elastic arteries > muscular arteries > arterioles > capillaries > venules > veins > venae cavae
anastomotic arteries
-form a link between the main arteries supplying an area
-if one artery supplying an area is blocked these arteries provide a collateral (alternate) circulation
capillaries
-single layer of endothelial cells sat on very thin basement membrane
-basement membrane permeable to water and other SMALL molecules
-diameter varies from 3-4µm to about 170µm (e.g. liver)
types of capillary
-continuous
-fenestrated
-discontinuous (sinusoidal)
continuous capillaries
-diffusion distance around 300µm
-complete endothelial cell lining with tight junctions between them (incomplete so leave intercellular clefts)
-solute exchange can occur through intercellular clefts or caveolae-mediated transport
-occurs in fat, muscle + the nervous system (almost all vascularised tissues)