The Cardiovascular System

The Cardiovascular System - : thick-walled arteries near...

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The Cardiovascular System: Blood Vessels Structure of Blood Vessel Walls : - tunica interna ( tunica intima) : innermost tunic (layer) o endothelium (simple squamous epithelium) lining lumen of all vessels o larger vessels have basement membrane - tunica media : middle tunic o o generally thickest layer in arteries o smooth muscle innervated by vasomotor fibers of sympathetic division of ANS vasoconstriction: reduction in lumen diameter due to smooth muscle contraction vasodilation: increase in lumen diameter due to smooth muscle relaxation - tunica externa ( tunica adventitia ) : outermost tunic o surrounding structures o o vasa vasorum: system of blood vessels nourishing tunica externa in larger vessels Arterial system - arteries : transport blood away from the heart o elastic (conducting) arteries
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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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The Cardiovascular System - : thick-walled arteries near...

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