Midterm (Chapters 18-21)

• Flow is also called volume flow rate
• What are the 3 forms of blood flow ?

  Pulsatile, phasic, and steady
• Pulsatile flow occurs when blood moves with a variable velocity die to cardiac contraction.
• Pulsatile flow is more commonly seen in the arterial circulation.
• Phasic flow occurs when blood moves with variable velocity die to respiration.
• Phasic flow is more commonly seen in the venous circulation.
• Steady flow occurs when a fluid's velocity is constant
• Steady flow can be found in the venous circulation when individuals stop breathing for a brief moment.
• Laminar flow is when the flow streamlines are parallel.
• What are the two forms of laminar flow ?

  Plug flow and parabolic flow
• Plug flow occurs when all of the layers and blood cells travel at the same velocity
• Parabolic flow has a bullet shaped profile; velocity is higher in the center and lowest at the vessel wall
• What is the Reynolds number ?

  predicts whether flow is laminar or turbulent.
• What is the Reynolds number for laminar flow ?

  less than 1500
• What is turbulent flow ?

  Chaotic flow patterns in many different directions and at many speeds
• Turbulence is often associated with cardiovascular pathology
• What is the sound associated with turbulence ?

  murmur or bruit
• What is the tissue vibration associated with turbulence ?

  thrill
• What is the Reynolds number for turbulent flow ?

  greater than 2000
• Why does blood move from one location to another ?

  Due to an energy gradient
• What are the three forms of energy associated with blood ?

  Kinetic, pressure, and gravitational
• Kinetic energy is associated with a moving object.
• Kinetic energy is determined by what two factors ?

  Mass and velocity
• What is pressure energy ?

  Form of potential energy which has the ability to perform work
• What must pressure overcome to create flow ?

  Resistance
• What is gravitational energy ?

  A form of potential energy associated with any elevated object
• What are the three ways energy is lost as blood flows through the circulation ?

  Viscous loss, frictional loss, and inertial loss
• What is viscosity ?

  thickness of a fluid
• The higher the viscosity, the more energy lost
• Viscosity is measured in units of Poise.
• Viscous energy loss in blood is determined by hematocrit.
• The lower the hematocrit, the less viscosity blood has.
• What is frictional loss ?

  Loss of energy into heat as one object rubs against another
• What is inertial energy loss ?

  Energy is lost when the speed of a fluid changes
• What is inertia ?

  tendency of a fluid to resist changes in its velocity
• Inertia energy loss occurs during 3 events:

  Pulsatile flow, phasic flow, and at a stenosis
• Velocity increases as the vessel narrows.
• Velocity decreases as blood flows out of the stenosis into a vessel segment of normal diameter.
• What is a stenosis ?

  narrowing in the lumen of a vessel
• What are some effects stenosis may have on blood flow ?

  Changes in flow direction, increased velocity within stenosis, post stenotic turbulence, pressure gradient across the stenosis, and loss of pulsatility