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blood pressure (13.2 MECHANISMS THAT REGULATE BLOOD FLOW (A.factors…
blood pressure
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13.1
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- strong and thick-walled vessels
- walls have 3 distinct layers
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- carry blood under great pressure
- carry blood that is high in oxygen and low in carbon dioxide except pulmonary arteries
- branch and give rise to thinner vessels called arterioles
- may unite with branches of other arteries supplying same region forming anastomoses (providing alternate routes)
VENULES and VEINS
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venules composed of a tunica externa, tunica intima extend from capillaries and merge together to form veins
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C. Capillaries smallest, thinnest blood vessels
1.permit exchange of gases, nutrients and wastes between blood and tissues
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- regulation of capillary blood flow
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Capillary Exchange gases, nutrients and wastes are exchanged between blood in capillaries and tissues in 3 ways:
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b.substances include oxygen,CO2 glucose and hormones
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colloid osmotic pressure-pressure (osmosis)draws fluid back into capillary
net affect is fluid loss at the beginning of capillary bed but most regained by end of capillary bed
fluid not retained enters lymphatic vessels
B. arterioles
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- deliver blood to capillaries in tissues
- play a major role in regulating blood flow to capillaries, and therefor regulate blood pressure
a. Vasoconstriction(contraction)=decrease vessel volume=decreased blood flow=increased blood pressure
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