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Unformatted text preview: : thick-walled arteries near heart (aorta & major branches) large diameter, low resistance most elastic arteries; elastin present in all 3 tunics (mostly in tunica media) fairly continuous blood flow; passively expand & contract to accommodate blood volume o muscular (distributing) arteries : branch from elastic arteries to distribute blood to body organs includes most named arteries proportionately thickest tunica media; more active than elastic Arteries in vasoconstriction o arterioles : vary in size; lead from muscular arteries to capillary beds blood flow into capillary beds determined by arteriole diameter if arterioles constrict, tissue is largely bypassed Capillaries : smallest blood vessels; exchange materials (gases, nutrients, hormones, etc.) in blood with tissues- only tunica interna (endothelium)- pericytes: smooth muscle-like cells at intervals to stabilize capillary wall- capillary types: PAGE1...
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- Fall '10