Factors Involved in Blood Circulation

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  • A. Blood Flow - the actual VOLUME of blood moving through a particular site (vessel or organ) over a certain TIME period (liter/hour, ml/min)
  • B. Blood Pressure - the FORCE exerted on the wall of a blood vessel by the blood contained within (millimeters of Mercury; mm Hg)
    • Blood pressure = the systemic arterial pressure of large vessels of the body (mm Hg)
  • C. Resistance to Flow (Peripheral Resistance) - the FORCE resisting the flow of blood through a vessel (usually from friction)
    • 1. Viscosity - a measure of the "thickness" or "stickiness" of a fluid flowing through a pipe
      • a. V water <>
      • b. water flows easier than blood
    • 2. Tube length - the longer the vessel, the greater the drop in pressure due to friction
    • 3. Tube diameter - smaller diameter = greater friction
  • D. Relation Between Blood Flow, Pressure, Resistance
        • difference in blood pressure ( P)
  • Blood Flow (F) = --------------------------------------------
        • peripheral resistance (R)
    • a. Increased P -> increased flow
    • b. Decreased P -> decreased flow
    • b. Increased R (vasoconstriction) -> DECREASED flow
    • c. Decreased R (vasodilation) -> INCREASED flow

Category: Physiology Notes



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