1. Blood Vessels arteries carry blood away from ventricles of heart
arterioles
receive blood from arteries
carry blood to capillaries
capillaries
sites of exchange of substances between blood and body cells
venules
receive blood from capillaries
veins
carry blood toward ventricle of heart
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2. Arteries and Arterioles
Artery
thick strong wall
endothelial lining
middle layer of smooth muscle and elastic tissue
outer layer of connective tissue
carries blood under relatively high pressure
Arterioles
thinner wall than artery
endothelial lining
some smooth muscle tissue
small amount of connective tissue
helps control blood flow into a capillary
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3. Walls of Artery and Vein
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4. Arteriole smallest arterioles only have a few smooth muscle fibers
capillaries lack muscle fibers
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5. Metarteriole
connects arteriole directly to venule
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6. Capillaries smallest diameter blood vessels
extensions of inner lining of arterioles
walls are endothelium only
semipermeable
sinusoids – leaky capillaries
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7. Capillary Network
15-36

8. Regulation of Capillary Blood Flow
Precapillary sphincters
may close a capillary
respond to needs of the cells
low oxygen and nutrients cause sphincter to relax
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9. Exchange in the Capillaries
water and other substances leave capillaries because of net outward pressure at the capillaries’s arteriolar ends
water enters capillaries’s venular ends because of a net inward pressure
substances move in and out along the length of the capillaries according to their respective concentration gradients
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10. Venules and Veins Venule thinner wall than arteriole
less smooth muscle and elastic tissue than arteriole
Vein
thinner wall than artery
three layers to wall but middle layer is poorly developed
some have flaplike valves
carries blood under relatively low pressure
serves as blood reservoir
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11. Venous Valves
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12. Blood Volumes in Vessels
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13. Arterial Blood Pressure
Blood Pressure – force the blood exerts against the inner walls of the blood vessels
Arterial Blood Pressure
rises when ventricles contract
falls when ventricles relax
systolic pressure – maximum pressure
diastolic pressure – minimum pressure
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14. Pulse
alternate expanding and recoiling of the arterial wall that can be felt
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15. Factors That Influence Arterial Blood Pressure
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16. Control of Blood Pressure
Controlling cardiac output and peripheral resistance regulates blood pressure
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17. Control of Blood Pressure
If blood pressure rises, baroreceptors initiate the cardioinhibitory reflex, which lowers the blood pressure
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18. Control of Blood Pressure
Dilating arterioles helps regulate blood pressure
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19. Venous Blood Flow not a direct result of heart action
depends on skeletal muscle contraction
depends on breathing
depends on venoconstriction
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