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Frequently Asked Questions
| Normal Venous Circulation |
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Q: What is the main function of
the deep venous circulation?
A: The deep venous
circulation returns blood from the tissues (the extremity) to the
heart. To achieve this goal, veins are designed for low pressure, are
enclosed within contracting muscle, and contain valves that prevent
backflow (reflux). |
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Q: What characteristics do veins have
that enable them to return blood to the heart?
A: Veins have (a) valves that prevent
backward flow of blood and (b) thin walls capable of expanding to a much
larger diameter. The fact that veins are located within contracting muscle
is another significant third factor, but is not intrinsic to the vein wall. |
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Q: At what three sites does a
peripheral pump mechanism contribute to the return flow of blood from the
extremity toward the heart? Which is the main contributor?
A: The
thigh, calf, and foot are the three main sites, and the calf is the main
contributor. |
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Q: How much of the blood contained
within the deep veins of the calf is expelled by calf contraction?
A: Sixty percent
of the blood is expelled into the popliteal vein (below the knee) with a
single, normal calf muscle contraction. |
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