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70 Cards in this Set
- Front
- Back
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Hemodynamics is the study of |
Blood moving through circulatory system |
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Flow Also called |
Volume flow rate Indicates the volume of blood moving during a particular time |
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Units of flow |
Volume divided by time, such as liters per minute, for example, 5 L/min |
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Velocity indicates |
Do you speed or swiftness of a fluid moving from one location to another Velocity answers the question how fast? |
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The units of velocity are |
Distance divided by time, such as cm/sec For example, 200 cm/s |
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Three basic forms of blood flow r |
Pulsatilla Phasic Steady |
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Pulsatile flow occurs when |
When blood moves with a variable velocity |
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Blood accelerates and decelerates as a result of (pulsatile) |
Cardiac contraction Therefore pulsatile flow commonly appears in arterial Circulation |
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Phasic flow also occurs when |
Blood moves with the variable velocity |
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Blood Accelerates and decelerates as a result of |
Respiration Therefore, phasic flow often appears in the Venous Circulation |
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Steady flow occurs when |
A fluid moves at a constant speed or velocity Water flowing through a garden hose is an example of steady flow |
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Steady flow is present in the venous circulation When |
Individual stop breathing for a brief moment |
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Laminar flow is when |
D flow streamlines are aligned in parallel |
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The word lamina means |
Layer |
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Laminar flow is characterized by |
Layers of blood that travel at individual speeds |
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Laminar flow patterns are commonly found in |
Normal physiological states |
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Laminar flow has two |
Plug flow and parabolic flow |
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Plug flow occurs when |
All of the layers and blood cells travel at the same velocity |
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Parabolic flow has a |
Bullet shaped profile, velocity is highest in the center of the lumen, and gradually decreases to its minimum at the Vessel wall |
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Both plug in parabolic patterns are |
Laminar and associated with normal physiology |
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Laminar flow is |
Silent flow |
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The Reynolds number predicts |
Weather flow is laminar or turbulent. The Reynolds number for laminar flow is less than 1500 |
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When blood moves from regions of higher energy to lower energy this is called |
Energy gradient |
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What event provides energy to the circulating blood |
Energy is imparted to blood by the contraction of the heart during Systole |
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Several forms of energy are’s associated with blood |
Kinetic Pressure Gravitational |
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The total energy at a specific location within the circulation is |
The sum of all three energy forms |
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Kinetic Energy is determined by two factors |
An object mass The speed at which it moves |
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Pressure energy is a form of |
Stored or potential energy |
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Pressure is a major form of energy for |
Circulating blood and create flow by overcoming resistance Example is whip cream can |
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Gravitational energy is a form |
Stored or potential energy |
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Identical objects at the same height have |
The same gravitational energy |
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As blood flows through the circulation, energy is lost in three ways |
Viscous loss Frictional loss Inertial loss |
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Viscosity describes the |
Thickness of a fluid Example, honey is viscose, where is alcohol is not More energy is lost with movement of high viscosity fluids |
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Viscosity is measured in units of |
Poise Test question |
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Viscus energy loss in blood is determined by |
Hematocrit |
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Hematocrit Is the |
Percentage of blood made up of red blood cells Normal value is approximately 45% |
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Frictional losses occur when |
Flow energy is converted to heat as one object rubs against another Example is blood sliding across vessel walls creates heat, and is an example of friction loss |
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Sir Isaac Newton stated that |
Objects at rest tends to stay at rest and object in motion tends to stay in motion |
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Inertia relate to |
The tendency of a fluid to resist changes in its velocity |
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Inertial energy loss occurs during three events |
Pulsatile flow (usually found in the arterial circulation) Phasic flow (usually found in the venous circulation) Velocity changes at a stenosis |
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Velocity increases as the vessel |
Narrows Maximum velocity exist where the vessel is narrowest |
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Velocity decreases as |
Blood flows out of the stenosis into a vessel segment of normal diameter |
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Stenosis is |
A narrowing in the lumen of a vessel |
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Stenosis may have these effects on blood flow Bern |
Change inflow direction Increase velocity as vessel narrows Turbulence downstream from stenosis Pressure gradient across the stenosis Loss of pulsatility |
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What is post stenotic turbulence |
Turbulence downstream from the stenosis |
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Bernoulli’s principle describes |
The relationship between velocity and pressure in a moving fluid This principle is derived from the principle of conservation of energy |
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Bernoulli Principle states that |
With a steady flow, the sum of all forms of energy is the same everywhere Kinetic energy and pressure energy remain constant |
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The law of conservation of energy states that |
Energy is neither created nor destroyed, it is simply converted from one form to another |
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Kinetic energy of blood increases as |
It speeds up to the stenosis from location a to location B |
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Pressure gradient = Pressure gradient increases when either? |
Flow x resistance Flow increases, or resistance increases |
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Flow increases when either? |
Pressure gradient increases or resistance decreases |
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Ohms law |
The movement of fluid through a tube in the movement of electricity through a wire or similar |
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Pressure in a fluid system is called |
Voltage in an electrical system |
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Ohms law describes Voltage = |
Current X resistance |
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Flow in a fluid system is called |
Current In a electric one Resistance has the same name in both systems |
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Electrical resistance is reported in units of |
Ohms |
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In the circulatory system the resistance vessels are called |
Arterials |
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The cross-sectional shape of a vein during normal function is |
Flatten or hourglass shaped |
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What is the typical resistance of veins? |
Veins, like arteries, are usually low resistance vessels |
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When Venus in flow increases during exercise the |
Cross-sectional shape of a vein changes from hour glass to oval and then to round This allows the beans to accommodate a large volume increase with a very small increase in pressure |
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Have you ever noticed the sensation of pressure on your ears when you dive to the bottom of a swimming pool, the source of this sensation is the weight of water pressing on your eardrum and this is called |
Hydrostatic pressure |
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Hydrostatic pressure is pressure related to |
The weight of blood pressing on a vessel measured at a height above or below heart level |
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Units of hydrostatic pressure or |
mmHg |
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The significance of hydrostatic pressure is clinical medicine is demonstrated when |
Measuring a patient’s blood pressure |
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Pressures are accurately assessed when the measurement is made ass |
The level of the heart |
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When laying supine all parts of the body are at the same level as the heart and the? |
Hydrostatic pressure is zero everywhere |
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Add locations below heart level such as the ankle, hydrostatic pressure is |
Positive, the measured pressure will be higher than the true circulatory pressure |
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Add locations above the level of the heart, such as the year, hydrostatic pressure is |
Negative, the measured pressure will be lower than the true circulatory pressure |
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Measured pressure equals |
Circulatory pressure + hydrostatic pressureu |
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When standing... hydrostatic pressure |
Back (Definition) |
