Factors Involved in Blood Circulation

• 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