Circulatory System Heart _ blood vessels _veins _ arteries_

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Circulatory System Heart _ blood vessels _veins _ arteries_ Powered By Docstoc
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                          Blood Vessels

  Arteries carry oxygenated blood away from the heart.
 Arteries
  Arteries consist of 3 walls inner, middle and outer. When the
    heart contracts blood surges from the heart into the arteries
    under high pressure.

  Blood from the arteries passes into smaller arteries called
   arterioles then smaller vessels called capillaries. The
   diameter of a capillary is so small red blood cells need to travel
   through the vessels in single file.

  Vasodilation is an increase in the diameter of the blood vessel,
   increasing the blood flow and the amount of oxygen to the
   tissues. Allowing those tissues to benefit from increased blood
   flow. (example: in the case of an injury or infection)

  Vasoconstriction is a reduction in the diameter of the blood
   vessels decreasing blood flow and the amount of oxygen to the
   tissues.

  Capillaries are the site of fluid and gas exchange between the
   blood and body cells.

 Veins
  Veins carry deoxygenated blood back to the heart.

  Pressure in the smaller capillaries which lead to larger venules
   is much lower than in the arteries, therefore a series of one-way
   valves and skeletal muscles help venous blood flow.

				
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posted:8/19/2012
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