The Vessels
Vessel Anatomy
• Vessel Layers/Tunics
– Tunica Intima: Inner most layer in direct
contact with the blood
– Tunica Media: Muscular layer of the vessel
• Smooth muscle
• Involuntary
– Tunica Externa/Adventitia: Connective tissue,
outer sheath
Oxygenated Blood
• Arteries:
– Thickest walls due to larger tunica media
(more muscle)
– With out pressure, artery walls constrict due
to large muscle mass
– Very elastic and contractible
– Can actively change diameter via ANS
• Stimulated = vasoconstriction
• Relaxation/Inhibited = vasodilatation
Oxygenated Blood
• Arterioles:
– Very small arteries
– Large resistance to blood flow
• Similar to putting you finger over a garden hose
– Aneurysms: Rupture of vessel walls due to
increased pressure
• Aortic aneurysm: death within minutes
Exchange Vessels
• Capillaries:
– Very, very small
– Huge Surface Area
– Intertwine throughout all tissues within the
body
• Body worlds vessel exhibits
– Vessel walls are only one cell thick
• CO2 and O2 can pass directly though these walls
Deoxygenated Blood
• Venules:
– Smallest veins
– Receive unoxygenated
blood from the
capillary beds
Unoxygenated Blood
• Medium Sized Veins
– Most veins within your body
– Have valves that help prevent the backflow of
blood
– Muscle movement also helps move blood
along
• Varicose veins
• Large Veins
– Superior and Inferior vena cava
Blood Flow
1.
2.
3.
4.
5.
6.
7.
Aorta:
Arteries:
Arterioles:
Capillaries:
Venules:
Medium Sized Veins:
Large Veins:
Blood Flow Dynamics
• Flow is proportional to change in pressure
over resistance
– F≈ ∆P/R
– Flow is directly proportional to pressure
• Pressure ↑ then flow ↑
• Pressure ↓ flow ↓
– Flow is inversely proportional to resistance
• Resistance ↑ then flow ↓
• Resistance ↓ then flow ↑
Blood Flow Dynamics
• Resistance is greatest in arterioles:
– What happens to Flow?
• Pressure is greatest in Aorta:
– What is the effect on flow?
– Greatest ∆P occurs between aorta and
capillaries.
• What happens to flow?