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Three principle categories of blood vessels
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Arteries, veins & capillaries
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Arteries
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Efferent vessels- carry blood away from heart
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Veins
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Afferent vessels- carry blood back to heart
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Capillaries
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Microscopic, thin walled vessels that connect the smallest arteries to teh smallest veins
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Walls of arteries are composed of 3 layers of
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Tunics
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Tunica interna
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Lines inside of the vessel- exposed to blood- consists of simple squamos epith called endothelium
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Tunica media
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Mid layer- thickest-smooth muscle, collagen,elastic tiss- strengthen the vess and prevent bp from rupturing them & to provide vasomotion
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Vasomotion
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Changes in diameter of a blood vessel
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Tunica externa
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Outer most layer- loose connect tiss often merges w. neigh vess anchors the vess and provides pass4small nerves, lymph vess& smaller blood vess
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Vasa vasorum
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Small vessels that supply blood to at least the outer half of the wall of a larger vessel
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Resistance vessles
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A.k.a arteries. bc relatively strong resilient tiss struct that resists high bp- constructed to w/stand surges
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Conducting ( elastic or large) arteries
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BIGGEST-expand during ventricular systole to receive blood& recoil during diastole.sub to highest bp& have elastic tiss
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Distributing (muscular or medium) arteries
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Smaller branches that distrib blood to specif organs- interestate highway- 40 layers of smooth musc
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Resistance ( small) arteries
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Too variable in # and location to be given individual names- 25 layers of smooth musc & relatively little elastic tiss
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Arterioles
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Smallest of the resistance arteries 40-200Mm w/ only one to 3 layers of smooth muscle
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