The Vessels

Vessel AnatomyVessel Anatomy• Vessel Layers/TunicsVessel Layers/Tunics

– Tunica Intima: Inner most layer in direct Tunica Intima: Inner most layer in direct contact with the bloodcontact with the blood

– Tunica Media: Muscular layer of the vesselTunica Media: Muscular layer of the vessel•Smooth muscleSmooth muscle• InvoluntaryInvoluntary

– Tunica Externa/Adventitia: Connective Tunica Externa/Adventitia: Connective tissue, outer sheathtissue, outer sheath

Oxygenated BloodOxygenated Blood• Arteries:Arteries:

– Thickest walls due to larger tunica media Thickest walls due to larger tunica media (more muscle)(more muscle)

– With out pressure, artery walls constrict due With out pressure, artery walls constrict due to large muscle massto large muscle mass

– Very elastic and contractibleVery elastic and contractible– Can actively change diameter via ANSCan actively change diameter via ANS

•Stimulated = vasoconstrictionStimulated = vasoconstriction•Relaxation/Inhibited = vasodilatationRelaxation/Inhibited = vasodilatation

Oxygenated BloodOxygenated Blood• Arterioles: Arterioles:

– Very small arteriesVery small arteries– Large resistance to blood flowLarge resistance to blood flow

•Similar to putting you finger over a garden Similar to putting you finger over a garden hosehose

– Aneurysms: Rupture of vessel walls due Aneurysms: Rupture of vessel walls due to increased pressureto increased pressure•Aortic aneurysm: death within minutesAortic aneurysm: death within minutes

Exchange VesselsExchange Vessels• Capillaries:Capillaries:

– Very, very smallVery, very small– Huge Surface AreaHuge Surface Area– Intertwine throughout all tissues within the Intertwine throughout all tissues within the

bodybody•Body worlds vessel exhibitsBody worlds vessel exhibits

– Vessel walls are only one cell thickVessel walls are only one cell thick•CO2 and O2 can pass directly though these CO2 and O2 can pass directly though these

wallswalls

Deoxygenated BloodDeoxygenated Blood• Venules: Venules:

– Smallest veinsSmallest veins– Receive Receive

unoxygenated unoxygenated blood from the blood from the capillary bedscapillary beds

Unoxygenated BloodUnoxygenated Blood• Medium Sized VeinsMedium Sized Veins

– Most veins within your bodyMost veins within your body– Have valves that help prevent the Have valves that help prevent the

backflow of bloodbackflow of blood– Muscle movement also helps move blood Muscle movement also helps move blood

alongalong•Varicose veinsVaricose veins

• Large VeinsLarge Veins– Superior and Inferior vena cavaSuperior and Inferior vena cava

Blood FlowBlood Flow1.1. Aorta:Aorta:2.2. Arteries:Arteries:3.3. Arterioles:Arterioles:4.4. Capillaries:Capillaries:5.5. Venules:Venules:6.6. Medium Sized Veins:Medium Sized Veins:7.7. Large Veins:Large Veins:

Blood Flow DynamicsBlood Flow Dynamics• Flow is proportional to change in Flow is proportional to change in

pressure over resistancepressure over resistance– F≈ ∆P/RF≈ ∆P/R– Flow is directly proportional to pressureFlow is directly proportional to pressure

•Pressure ↑ then flow ↑ Pressure ↑ then flow ↑ •Pressure ↓ flow ↓Pressure ↓ flow ↓

– Flow is inversely proportional to resistanceFlow is inversely proportional to resistance•Resistance ↑ then flow ↓Resistance ↑ then flow ↓•Resistance ↓ then flow ↑Resistance ↓ then flow ↑

Blood Flow DynamicsBlood Flow Dynamics• Resistance is greatest in arterioles:Resistance is greatest in arterioles:

– What happens to Flow?What happens to Flow?• Pressure is greatest in Aorta:Pressure is greatest in Aorta:

– What is the effect on flow?What is the effect on flow?– Greatest Greatest ∆P occurs between aorta and ∆P occurs between aorta and

capillaries.capillaries.•What happens to flow?What happens to flow?