Gastrovascular Cavities• Simple animals, such as cnidarians,have a body wall only two cells thickthat encloses a gastrovascular cavity• This cavity functions in both digestionand distribution of substancesthroughout the body• Some cnidarians, such as jellies, haveelaborate gastrovascular cavitiesLE 42-2MouthRadial canalCircularcanal5 cmOpen and Closed CirculatorySystems• More complex animals have either open orclosed circulatory systems• Both systems have three basic components:– A circulatory fluid (blood or hemolymph)– A set of tubes (blood vessels)– A muscular pump (the heart)• In insects, other arthropods, and mostmolluscs blood bathes the organsdirectly in an open circulatory system• There is no distinction between bloodand interstitial fluid, and this generalbody fluid is more correctly calledhemolymphLE 42-3Hemolymph in sinusessurrounding organsHeartAnteriorvesselOstiaTubular heartAn open circulatory system.LateralvesselA closed circulatory system.Auxiliary heartsVentral vesselsDorsal vessel(main heart)Small branch vesselsin each organInterstitialfluidHeart• In a closed circulatory system,blood is confined to vessels and isdistinct from the interstitial fluid• Closed systems are more efficientat transporting circulatory fluids totissues and cellsLE 42-4FISHESGill capillariesAMPHIBIANSLung and skin capillariesREPTILES (EXCEPT BIRDS)Lung capillariesMAMMALS AND BIRDSLung capillariesGillcirculationHeart:Ventricle (V)Atrium (A)ArteryVeinSystemiccirculationSystemic capillariesSystemic capillariesSystemiccircuitPulmocutaneouscircuitRightLeftAAVAVAVSystemic capillariesRightLeftPulmonarycircuitRightsystemic aortaVAVSystemic capillariesRight LeftPulmonarycircuitASystemiccircuitLeftsystemic aortaSystemic circuits include all body tissues except lungs. Note that circulatory systems are depictedas if the animal is facing you: with the right side of the heart shown at the left and vice-versa.LE 42-5Anteriorvena cavaPulmonaryarteryCapillariesof right lungAortaPulmonaryveinRight atriumRight ventriclePosteriorvena cavaCapillaries ofabdominal organsand hind limbsPulmonaryveinLeft ventricleLeft atriumAortaPulmonaryarteryCapillaries ofhead andforelimbsCapillariesof left lungLE 42-6Right atriumPosteriorvena cavaPulmonaryveinsAnteriorvena cavaPulmonary arteryPulmonaryveinsRightventricleAortaSemilunarvalveAtrioventricularvalvePulmonaryarteryLeft atriumSemilunarvalveAtrioventricularvalveLeftventricle• The heart contracts and relaxes in arhythmic cycle called the cardiac cycle• The contraction, or pumping, phase iscalled systole• The relaxation, or filling, phase iscalled diastoleTo adjust blood pressure independently inthe capillaries of the gas-exchange surfaceand in the capillaries of the general bodycirculation, an organism would need– A. an open circulatory system.– B. a hemocoel.– C. a lymphatic system.– D. a two-chambered heart.– E. a four-chambered heart.LE 42-7SemilunarvalvesclosedAV valvesopen0.1 sec0.3 sec0.4 secAtrial andventriculardiastoleAV valvesclosedVentricular systole;atrial diastoleSemilunarvalvesopenAtrial systole;ventriculardiastole• The heart rate, also called the pulse, isthe number of beats per minute• The cardiac output is the volume ofblood pumped into the systemiccirculation per minuteMaintaining the Heart’s RhythmicBeat• Some cardiac muscle cells are self-excitable, meaning they contract withoutany signal from the nervous system• The sinoatrial (SA) node, or pacemaker,sets the rate and timing at which cardiacmuscle cells contract• Impulses from the SA node travel to theatrioventricular (AV) node• At the AV node, the impulses are delayedand then travel to the Purkinje fibers thatmake the ventricles contract• Impulses that travel during the cardiaccycle can be recorded as anelectrocardiogram (ECG or EKG)LE 42-8Pacemakergenerates wave ofsignals to contract.Signals are delayedat AV node.Signals passto heart apex.Signals spreadthroughoutventricles.SA node(pacemaker)ECGAV nodeBundlebranchesHeartapexPurkinjefibers• The pacemaker is influenced bynerves, hormones, bodytemperature, and exerciseConcept 42.3: Physical principlesgovern blood circulation• The physical principles that governmovement of water in plumbingsystems also influence thefunctioning of animal circulatorysystemsBlood Vessel Structure andFunction• The “infrastructure” of the circulatorysystem is its network of blood vessels• All blood vessels are built of similartissues and have three similar layersLE 42-9EndotheliumEndotheliumSmoothmuscleConnectivetissueCapillary100 µmBasementmembraneEndotheliumSmoothmuscleConnectivetissueValveArteryArterioleVenuleVeinArteryVein• Structural differences in arteries, veins,and capillaries correlate with functions• Arteries have thicker walls thataccommodate the high pressure ofblood pumped from the heart• In the thinner-walled veins, blood flowsback to the heart mainly as a result ofmuscle actionLE 42-10Valve (open)Skeletal muscleValve (closed)Direction of blood flowin vein (toward heart)Blood Flow Velocity• Physical laws governing movement of fluidsthrough pipes affect blood flow and bloodpressure• Velocity of blood flow is slowest in thecapillary beds, as a result of the highresistance and large total cross-sectionalareaLE 42-11SystolicpressureVenae cavaeVeinsVenulesCapillariesArteriolesArteriesAortaDiastolicpressurePressure (mm Hg)120100806040200Area (cm2)5,0004,0003,0002,0001,0000Velocity
View Full Document
Unlocking...