The Vessels

Vessel Anatomy Vessel Layers/Tunics Vessel Layers/Tunics –Tunica Intima: Inner most layer in direct contact with the blood –Tunica Media: Muscular layer of the vessel Smooth muscle Smooth muscle Involuntary Involuntary –Tunica Externa/Adventitia: Connective tissue, outer sheath

Oxygenated Blood Arteries: 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 Stimulated = vasoconstriction Relaxation/Inhibited = vasodilatation Relaxation/Inhibited = vasodilatation

Oxygenated Blood Arterioles: Arterioles: –Very small arteries –Large resistance to blood flow Similar to putting you finger over a garden hose Similar to putting you finger over a garden hose –Aneurysms: Rupture of vessel walls due to increased pressure Aortic aneurysm: death within minutes Aortic aneurysm: death within minutes

Exchange Vessels Capillaries: Capillaries: –Very, very small –Huge Surface Area –Intertwine throughout all tissues within the body Body worlds vessel exhibits Body worlds vessel exhibits –Vessel walls are only one cell thick CO2 and O2 can pass directly though these walls CO2 and O2 can pass directly though these walls

Deoxygenated Blood Venules: Venules: –Smallest veins –Receive unoxygenated blood from the capillary beds

Unoxygenated Blood Medium Sized Veins 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 Varicose veins Large Veins Large Veins –Superior and Inferior vena cava

Blood Flow 1. Aorta: 2. Arteries: 3. Arterioles: 4. Capillaries: 5. Venules: 6. Medium Sized Veins: 7. Large Veins:

Blood Flow Dynamics Flow is proportional to change in pressure over resistance Flow is proportional to change in pressure over resistance –F≈ ∆P/R –Flow is directly proportional to pressure Pressure ↑ then flow ↑ Pressure ↑ then flow ↑ Pressure ↓ flow ↓ Pressure ↓ flow ↓ –Flow is inversely proportional to resistance Resistance ↑ then flow ↓ Resistance ↑ then flow ↓ Resistance ↓ then flow ↑ Resistance ↓ then flow ↑

Blood Flow Dynamics Resistance is greatest in arterioles: Resistance is greatest in arterioles: –What happens to Flow? Pressure is greatest in Aorta: Pressure is greatest in Aorta: –What is the effect on flow? –Greatest ∆P occurs between aorta and capillaries. What happens to flow? What happens to flow?