ch21ppt - 21-1Chapter 21The Cardiovascular System Blood...

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Unformatted text preview: 21-1Chapter 21The Cardiovascular System: Blood Vessels and Hemodynamics•Structure and function of blood vessels•Hemodynamics–forces involved in circulating blood•Major circulatory routes21-2Anatomy of Blood Vessels•Closed system of tubes that carries blood•Arteries carry blood from heart to tissues–elastic arteries–muscular arteries–arterioles•Capillaries are thin enough to allow exchange•Venules merge to form veins that bring blood back to the heart•Vasa vasorum is vessels in walls of large vessel21-3Arteries•Tunica interna (intima)–simple squamous epithelium known as endothelium–basement membrane–internal elastic lamina•Tunica media–circular smooth muscle & elastic fibers•Tunica externa–elastic & collagen fibers21-4Sympathetic Innervation•Vascular smooth muscle is innervated by sympathetic nervous system–increase in stimulation causes muscle contraction or vasoconstriction•decreases diameter of vessel–injury to artery or arteriole causes muscle contraction reducing blood loss (vasospasm)–decrease in stimulation or presence of certain chemicalscauses vasodilation•increases diameter of vessel•nitric oxide, K+, H+ and lactic acid cause vasodilation21-5Elastic Arteries•Largest-diameter arteries have lot of elastic fibers in tunica media•Help propel blood onward despite ventricular relaxation (stretch and recoil -- pressure reservoir)21-6Muscular Arteries•Medium-sized arteries with more muscle than elastic fibers in tunica media•Capable of greater vasoconstriction and vasodilation to adjust rate of flow–walls are relatively thick–called distributing arteries because they direct blood flow21-7Arterioles•Small arteries delivering blood to capillaries–tunica media containing few layers of muscle•Metarterioles form branches into capillary bed–to bypass capillary bed, precapillary sphincters close & blood flows out of bed in thoroughfare channel–vasomotion is intermittent contraction & relaxation of sphincters that allow filling of capillary bed 5-10 times/minute21-8Capillaries form Microcirculation•Microscopic vessels that connect arterioles to venules•Found near every cell in the body but more extensive in highly active tissue (muscles, liver, kidneys & brain)–entire capillary bed fills with blood when tissue is active–lacking in epithelia, cornea and lens of eye & cartilage•Function is exchange of nutrients & wastes between blood and tissue fluid•Structure is single layer of simple squamous epithelium and its basement membrane21-9Types of Capillaries•Continuous capillaries–intercellular clefts are gaps between neighboring cells–skeletal & smooth, connective tissue and lungs•Fenestrated capillaries–plasma membranes have many holes–kidneys, small intestine, choroid plexuses, ciliary process & endocrine glands•Sinusoids–very large fenestrations–incomplete basement membrane–liver, bone marrow, spleen, anterior pituitary, & parathyroid gland21-10Venules...
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This note was uploaded on 05/23/2010 for the course BIO 222 taught by Professor Brooks during the Spring '10 term at Prairie State College .

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ch21ppt - 21-1Chapter 21The Cardiovascular System Blood...

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