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

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Unformatted text preview: 21-1Chapter 21The Cardiovascular System: Blood Vessels and HemodynamicsStructure and function of blood vesselsHemodynamicsforces involved in circulating bloodMajor circulatory routes21-2Anatomy of Blood VesselsClosed system of tubes that carries bloodArteries carry blood from heart to tissueselastic arteriesmuscular arteriesarteriolesCapillaries are thin enough to allow exchangeVenules merge to form veins that bring blood back to the heartVasa vasorum is vessels in walls of large vessel21-3ArteriesTunica interna (intima)simple squamous epithelium known as endotheliumbasement membraneinternal elastic laminaTunica mediacircular smooth muscle & elastic fibersTunica externaelastic & collagen fibers21-4Sympathetic InnervationVascular smooth muscle is innervated by sympathetic nervous systemincrease in stimulation causes muscle contraction or vasoconstrictiondecreases diameter of vesselinjury to artery or arteriole causes muscle contraction reducing blood loss (vasospasm)decrease in stimulation or presence of certain chemicalscauses vasodilationincreases diameter of vesselnitric oxide, K+, H+ and lactic acid cause vasodilation21-5Elastic ArteriesLargest-diameter arteries have lot of elastic fibers in tunica mediaHelp propel blood onward despite ventricular relaxation (stretch and recoil -- pressure reservoir)21-6Muscular ArteriesMedium-sized arteries with more muscle than elastic fibers in tunica mediaCapable of greater vasoconstriction and vasodilation to adjust rate of flowwalls are relatively thickcalled distributing arteries because they direct blood flow21-7ArteriolesSmall arteries delivering blood to capillariestunica media containing few layers of muscleMetarterioles form branches into capillary bedto bypass capillary bed, precapillary sphincters close & blood flows out of bed in thoroughfare channelvasomotion is intermittent contraction & relaxation of sphincters that allow filling of capillary bed 5-10 times/minute21-8Capillaries form MicrocirculationMicroscopic vessels that connect arterioles to venulesFound 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 activelacking in epithelia, cornea and lens of eye & cartilageFunction is exchange of nutrients & wastes between blood and tissue fluidStructure is single layer of simple squamous epithelium and its basement membrane21-9Types of CapillariesContinuous capillariesintercellular clefts are gaps between neighboring cellsskeletal & smooth, connective tissue and lungsFenestrated capillariesplasma membranes have many holeskidneys, small intestine, choroid plexuses, ciliary process & endocrine glandsSinusoidsvery large fenestrationsincomplete basement membraneliver, bone marrow, spleen, anterior pituitary, & parathyroid gland21-10Venules...
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ch21ppt - 21-1Chapter 21The Cardiovascular System: Blood...

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