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CARDIOVASCULARSYSTEM:BLOODvessels
HumanAnatomyUnit3
InAnatomyToday
HistologyofBloodVessels
• Tunicaintima– endothelium– looseCT+simplesquamousepithelium
• Tunicamedia– smoothmuscle(notcardiac)– mayhaveelastin
• Tunicaexterna– adventitia– fibrousCTwithelastin
HistologyofBloodVessels
HistologyofBloodVessels
TypesofBloodVessels
• Arteries– resistancevessels– highpressure– carrybloodawayfromheart
• Capillaries– exchangevessels
• Veins– capacitancevessels– lowpressurelines– carrybloodtotheheart
Arteries
• Characteristics– Smallerdiameterthanveins
– thicktunicamedia– Lotsofelastin
• Function– carrybloodawayfromtheheart
– notalwaysoxygenated
TypesofArteries• Elastic(Conducting)
– Transportlargevolumesofblood– abundantelastin– Vasavasorum
• Muscular(Distribution)– Skeletalmuscleandinternalorgans– distributeto“lobes” ofanorgan
• Arterioles– Vasocontriction/vasodilation– Scatteredsmoothmusclefibers– smalldiameters,branchinto
capillaries– greatestresistancetobloodflow
Capillaries
Capillaries
• Structure– Tunicaintimaonly(endothelium)
– Precapillarysphincter– Metarteriole– Thoroughfarechannel
• Function– Diffusionandexchangeofsubstanceswithtissues
– Anastomosis
Sinusoids
• Liver,bonemarrow,adrenalgland
• Resemblefenestratedcapillariesbuthavelargerpores
• Thinnerbasallamina• Allowforbulkexchange• Lowflowrate
PortalCircuits
• Parallelcircuits– Artery– Capillary– Vein
• Portalcircuit– Artery– Capillary– Vein– Capillary– Vein
• Anastomosingcircuit
Veins
• Characteristics– Relativelylargediameters
– Thintunicamedia– Thicktunicaexterna– Largeveinshavevalves(especiallyinlegs)
• Functionofveins– Carrybloodbacktotheheart(notalwaysdeoxygenated)
TypesofVeins
• LargeVeins– Venacavae– SuperiorVCandinferiorVC– Drainbloodfrommostveins
• MediumVeins– Tributariestothevenacavae– Drainorgansandlobesoforgans
• Venules– Smallestofallveins– Draincapillaries
VenousValves
ArteriesvsVeinsCharacteristics Artery VeinDiameter Narrower Wider,oftencollapsedWallthickness Thicker ThinnerX-section Keepscircularshape collapsesThickesttunic Tunicamedia TunicaexternaFibers Moreelastic/collagen LessBloodpressure >90mmHginlarger Approx2mmHgBloodflow Awayfromheart TowardheartOxygenlevels Systemicarteries=highO2
Pulmonaryarteries=bloodlowinO2
Systemicveins=lowO2
Pulmonaryveins=highO2
Arteriesvs.Veins
Venules vs.Arterioles
DistributionofBlood
BloodVesselDistribution
MajorCVSCircuits
• Systemic– highvariableresistancecircuit– Includescoronarycirculation• thevasavasorumoftheheart
• Pulmonary– low,constantresistancecircuit
ThePulmonaryCircuit• Venousbloodreturn
– Venacavae– Coronarysinus
• Rightatrium• Tricuspidvalve• Rightventricle• Pulmonarysemilunarvalve• Pulmonarytrunk• Pulmonaryarteries• Capillariesoflungs
TheSystemicCircuit
• Capillariesoflungs• Pulmonaryveins• Leftatrium• Mitralvalve• Leftventricle• Aorticsemilunarvalve• Aorta• Branchesoffaorta• Capillariesofthetissues
FetalCirculation
• Allmajorbloodvesselsareinplacebythe3rdmonthofdevelopment&flowinginthesamedirection
• Placenta– Fetalstructure– Exchangesurfacebetweenfetalandmaternalblood• Gases• Nutrients• Wasteproducts• Hormones,toxins,etc….
PlacentaandUmbilicus
• Umbilicalvessels– PairedU.arteries(arisefrominternaliliaca.infetalpelvis)carrydeoxygenatedbloodfromthefetus-->placenta
– UnpairedU.veincarryoxygenatedbloodfromtheplacentaintotheductusvenosus
FetalShunts• Ductusvenosus
– connectedtoanintricatenetworkofveinsinthefetalliver
– Shuntsawayfromthelivercirculation
• Foramenovale– anopeningbetweentheatria
toshuntbloodfromR-L(avalve)
• Ductusarteriosus– ashuntbetweenthe
pulmonarytrunkandaorta– preventoverloadonthe
immaturelungs
FetalHeart
FetalCirculation
Allreturningbloodtothefetusproceedstohepaticveins,inferiorvenacavaandrightatrium
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