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