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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

Circulatory Systems

Transport & Maintenance

circulatory systems2
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
circulatory systems3
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
closed circulatory systems
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
circulatory systems7
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

closed circulatory systems8
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
closed circulatory systems9
Closed Circulatory Systems
  • systems with two-chambered hearts - fish
    • one circuit
      • atrium =>ventricle =>gills =>aorta =>body =>atrium
    • ventricular pressure is dissipated in gill capillaries
closed circulatory systems11
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
lungfish circulation schematic p 943
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

closed circulatory systems13
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
closed circulatory systems15
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
closed circulatory systems17
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
closed circulatory systems19
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
human circulatory system
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
human circulatory system24
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
human circulatory system26
Human Circulatory System
  • cardiac cycle
    • systole - contraction of ventricles
      • maximum pressure generated
      • major electrical event
    • diastole - relaxation of ventricles
      • minimum pressure
      • characteristic electrical signatures
human circulatory system29
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
human circulatory system31
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
human circulatory system33
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
human circulatory system35
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
human circulatory system37
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
human circulatory system39
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]
human circulatory system41
Human Circulatory System
  • veins
    • receive blood from capillaries under low pressure
    • contain one-way valves
    • blood is propelled by skeletal muscle contraction or gravity
human circulatory system43
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
human circulatory system46
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
human circulatory system48
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
human circulatory system50
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
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