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which part of blood has highest viscosity? (aorta, capillary,vena cava)

Discussion in 'Step I' started by HelicopterBen, Aug 14, 2009.

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  1. HelicopterBen

    HelicopterBen 7+ Year Member

    Nov 11, 2007
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  3. SomeDoc

    SomeDoc 10+ Year Member

    Apr 9, 2007
    Generally, it should be the same for all areas, as viscosity is an inherent physical property of a fluid.

    However, it is possible in the specific case with increased vessel hydrostatic or interstitial colloidal pressure, viscosity will be the highest in the capillaries. This is due to plasma filtering out of capillaries into the interstitium, leading to a higher cell to plasma ratio.
  4. DocTrek

    DocTrek Banned 2+ Year Member

    Aug 2, 2009
    Actually viscosity is lowest in capillaries and at the same time the velocity is the highest in them!
  5. Gozar

    Gozar 2+ Year Member

    Dec 16, 2007
    not true. velocity is lowest in the capillaries. total cross sectional are is highest in the capillaries, leading to the lowest velocity there. why would you want high velocity in the area of exchange?
  6. McGillGrad

    McGillGrad Building Mind and Body 10+ Year Member

    Dec 21, 2002
    woah... are you gents talking velocity or viscosity?
  7. Bernoull

    Bernoull 7+ Year Member

    Mar 24, 2007
    Ischioanal fossa
    If I recall from my biotransport phenomena class, hematocrit is highest in capillaries due to the rouleau effect hence viscosity is also highest at capillaries.

    Gozar's absolutely right about the inverse relation between velocity and total surface area.
  8. eduro25


    Jul 11, 2009
    In this link , they explain a little bit more about visscosity:


    They dont mention an area specifically , and I cant find that in BRS neither , so I think as Somedoc says , that if should be the same.

  9. Captopril

    Captopril 7+ Year Member

    May 10, 2008
    The ICU
    Last edited: Aug 20, 2009
  10. HospitalDO

    HospitalDO 2+ Year Member

    Aug 11, 2009
    Oops! Thanks for the reminder Gozar!
    Sorry fellows I've made a mistake!
    Viscosity is inversely related to velocity. Since, capillaries have the highest velocity they have the lowest viscosity!
    I hope the case is closed now!
  11. defcon8

    defcon8 Information ≠ Knowledge 7+ Year Member

    Jun 25, 2008
    I guess the answer is inversely related to what you just said then..:laugh:
  12. greenmatter


    Oct 3, 2014
    Excuse me if I bring up this thread but... this is confusing.

    It's true that flow velocity is LOWEST in capillaries - and that mostly occurs because capillaries DO have the highest total cross-section area.
    But you are implying that viscosity increases in capillaries which it doesn't seem right to me.


    What about plasma skimming?

    I guess there's a game of apparent and effective viscosity here.
  13. SBR249

    SBR249 7+ Year Member

    Mar 22, 2009
    well I think that the link above is pretty conclusive...viscosity is lower in small diameter vessels.

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