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Circulatory Systems. Transport & Maintenance. Circulatory Systems. transport to & from tissues nutrients, O 2 ; waste, CO 2 hormones maintain electrolyte balance of intercellular fluid transport to/from homeostatic organs small intestine delivers nutrients

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Circulatory systems l.jpg

Circulatory Systems

Transport & Maintenance


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Circulatory Systems

  • transport to & from tissues

    • nutrients, O2; waste, CO2

    • hormones

  • maintain electrolyte balance of intercellular fluid

  • transport to/from homeostatic organs

    • small intestine delivers nutrients

    • liver removes wastes, controls nutrients

    • kidney controls electrolytes, dumps wastes


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Circulatory Systems

  • some animals lack circulatory systems

    • aquatic environment fulfills same functions

  • some animals have open circulatory systems

    • the heart pumps interstitial fluid

    • vessels deliver interstitial fluid to tissues

    • interstitial fluids leave the vessels & bathe the cells of the tissues

    • interstitial fluids return to the heart

  • other animals have closed circulatory systems



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closed circulatory system of earthwormFigure 49.2


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Closed Circulatory Systems

  • components of closed circulatory systems

    • heart(s) - pump

    • vessels - transport conduits

    • blood -

      • transport medium

      • distinct from interstitial fluid

  • advantages over open system

    • speed

    • control of blood flow

    • cellular elements of blood remain in vessels


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Circulatory Systems

  • hearts

    • vertebrates have chambered hearts

      • valves impose one-way flow

    • number of chambers varies with phylogeny

    • blood circulates through one or two circuits

      • H => G.E.M. => B

      • H => G.E.M. => H => B

        pulmonary systemic

        circuit circuit


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Closed Circulatory Systems

  • vessels

    • arteries

      • transport blood away from heart

    • veins

      • transport blood toward heart

    • arterioles/venules

      • small arteries/veins

    • capillaries

      • connect arterioles to venules


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Closed Circulatory Systems

  • systems with two-chambered hearts - fish

    • one circuit

      • atrium =>ventricle =>gills =>aorta =>body =>atrium

    • ventricular pressure is dissipated in gill capillaries



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Closed Circulatory Systems

  • systems with two-chambered hearts - lungfish

    • modified for breathing air or water

      • out-pocketing of gut acts as a lung

      • some gill arteries supply blood to lung

      • some gill arteries deliver blood to aorta

      • gills exchange gases with water

    • partially separated atrium

      • right side => oxygenated blood => body

      • left side => deoxygenated blood => gills/lungs


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lungfish circulation schematicp. 943

* one pair of gill arteries delivers blood to lung

* two gill arches deliver blood directly to aorta

* “gilled” gill arches exchange gases with blood


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Closed Circulatory Systems

  • systems with three-chambered hearts - amphibians

    • two atria

      • left atrium receives pulmonary blood

      • right atrium receives systemic blood

    • ventricle anatomy limits mixing

      • deoxygenated blood travels to lung

      • oxygenated blood travels to body



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Closed Circulatory Systems

  • reptilian hearts provide further control

    • two atria receive blood from pulmonary & systemic circuits

    • partially separated ventricle supplies three vessels

      • pulmonary artery & two aortas

        • when breathing, the right aorta carries deoxygenated blood to the pulmonary circuit

        • when not breathing, both aortas carry blood to the systemic circuit



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Closed Circulatory Systems

  • crocodilian hearts have four chambers

    • two atria, two ventricles, two aortas

      • two aortas are bridged near their origins

      • when breathing, the left ventricle (& aorta) pressure is higher

        • deoxygenated blood goes to lungs

      • when not breathing, right aorta pressure is higher

        • pulmonary circuit is bypassed



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Closed Circulatory Systems

  • endotherm hearts have four chambers and one aorta

    • systemic/pulmonary circuits are separated

    • tissues receive highest possible [O2] (P1) under high pressure

    • lungs receive lowest possible [O2] (P2) under lower pressure




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Human Circulatory System

  • circulation

    • deoxygenated blood arrives at right atrium from inferior & superior vena cava

    • atrium pumps blood to right ventricle

    • ventricle pumps blood to pulmonary artery

      • backflow is prevented by atrioventricular valve

    • ventricle relaxes

      • backflow is prevented by pulmonary valve



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Human Circulatory System

  • circulation

    • oxygenated blood arrives at left atrium through pulmonary veins

    • atrium pumps blood into left ventricle

    • ventricle pumps blood to aorta

      • backflow is prevented by atrioventricular valve

    • ventricle relaxes

      • backflow is prevented by aortic valve



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Human Circulatory System

  • cardiac cycle

    • systole - contraction of ventricles

      • maximum pressure generated

      • major electrical event

    • diastole - relaxation of ventricles

      • minimum pressure

      • characteristic electrical signatures


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ventricular pressures & volumesFigure 49.4



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Human Circulatory System

  • heartbeat is myogenic

    • pacemaker cells occur at sinoatrial node

      • resting membrane potential depolarizes

      • at threshold, voltage gated Ca2+ channels open

      • K+ channels open to repolarize cells

      • K+ channels close slowly, allow gradual depolarization

    • autonomic nervous system regulates the rate of depolarization


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autonomic control of heart rateFigure 49.6Figure 49.8Figure 44. 9

norepinephrine

acetylcholine


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Human Circulatory System

  • contraction

    • the pacemaker action potential spreads across the atrial walls

    • atria contract

    • action potential is transmitted to ventricles through the atrioventricular node and the bundle of His

    • the action potential spreads to Purkinje fibers in ventricular muscle

    • ventricles contract


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origin and spread of cardiac contractionFigure 49.7


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Human Circulatory System

  • vascular system

    • arteries carry blood from heart

      • elastic tissues absorb pressure of heart contractions

      • smooth muscle allows control of blood flow by neural and hormonal signals


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artery structureFigure 49.10


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Human Circulatory System

  • vascular system

    • capillaries

      • fed by arterioles; drained by venules

      • exchange materials between blood & intercellular fluids

        • high total capacity; slow flow

        • thin walls


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capillary bedFigure 49.10


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Human Circulatory System

  • vascular system

    • capillaries

      • exchange materials by filtration, osmosis & diffusion

        • water & solutes move through capillary walls under pressure on the arteriole side

        • remaining solutes & diffusing CO2 produce a low osmotic potential

        • water returns to capillaries on the venule side


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water movement balanced between blood pressure & osmotic potentialFigure 49.12


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Human Circulatory System

  • [lymphatics

    • lymph vessels return excess tissue fluid to blood

      • lymphatic capillaries collect lymph

      • capillaries merge into larger vessels

      • vessels contain one-way valves

      • the major lymph vessel, the thoracic duct, empties into the superior vena cava

    • lymph nodes participate in lymphocyte production & phagocyte activity]


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vein structureFigure 49.10


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Human Circulatory System

  • veins

    • receive blood from capillaries under low pressure

    • contain one-way valves

    • blood is propelled by skeletal muscle contraction or gravity



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Human Circulatory System

  • blood - a fluid connective tissue

    • fluid matrix - plasma

      • dissolved gases, ions, proteins, nutrients, hormones, etc.

      • many components found in tissue fluid

    • cellular elements

      • red blood cells (erythrocytes)

      • white blood cells (leukocytes)

      • platelets


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blood componentsFigure 49.15


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human blood samplesbeforeand aftercentrifugation to separate red blood cells from serum


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Human Circulatory System

  • control & regulation of circulation

    • capillaries are subject to auto-regulation

      • pre-capillary sphincters and arterial smooth muscle are sensitive to

        • O2 & CO2 concentrations

        • accumulated waste materials



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Human Circulatory System

  • control & regulation of circulation

    • simultaneous auto-regulation of capillary beds produces systemic responses

      • changes in breathing, heart rate

      • changes in blood distribution

    • systemic control is neural or hormonal

      • sympathetic stimulation contracts most arteries; dilates skeletal muscle arteries

      • hormones constrict arteries in targeted tissues



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Human Circulatory System

  • control & regulation of circulation

    • autonomic control of circulation originates in medulla of brain stem

      • inputs arrive from

        • stretch receptors

        • chemosensors

        • higher brain centers

      • responses may be

        • direct - artery relaxation or contraction

        • indirect - release of epinephrine


Neural control of circulation is centered in the medulla figure 49 19 l.jpg
neural control of circulation is centered in the medullaFigure 49.19


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