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38 Cards in this Set

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Flow

Indicates the volume of blood moving during a particular time.


How much?


Velocity

Indicates the speed of a fluid moving from one location to another.


How fast?


3 basic forms of blood flow

* pulsatile


* phasic


* steady

Pulsatile flow

When blood moves with variable velocity as result of cardiac contraction.

In arterial circulation

Phasic flow

When blood moves with variable velocity with respiration.

In venous circulation

Steady flow

When a fluid moves at a constant speed or velocity.

Laminar flow

When the flow streamlines are aligned and parallel.

Normal flow

2 forms of laminar flow

* plug


* parabolic

Plug flow

When all layers & blood cells travel at same velocity.

Parabolic

Velocity highest in center of lumen, and gradually decreases to the vessel wall.

Bullet-shaped profile

Turbulent flow

Chaotic flow pattern in many directions & at many speeds.

Murmur / bruit

Sound associated with turbulence.

Thrill

Tissue vibration associated with turbulence.

Reynolds number

Predicts whether flow is laminar or turbulent.


Laminar < 1500


Turbulent > 2000

Forms of energy

* kinetic


* pressure


* gravitational

Kinetic energy

Associated with a moving object, determined by mass & speed.

Ping-pong vs golf ball

Pressure energy

A form of stored or potential energy, has the ability to do work.

Whipped cream can

Gravitational energy

Also stored or potential energy associated with elevated object.

Slide a hill vs flat surface

3 ways of energy loss

* viscous


* frictional


* inertial

Viscosity

Thickness of a fluid. More loss with high viscosity.

Honey vs alcohol

Hematocrit

The percentage of blood made of RBC.


Normal is 45%

Frictional

When flow energy converted to heat as objects rub.

Blood sliding across vessel

Inertia

Relates to tendency of fluid to resist changes in its velocity.

3 events of inertial loss

* Pulsatile flow


* phasic flow


* stenosis

Stenosis

Narrowing of the lumen of a vessel.

Effects of a stenosis

* change in flow direction


* increase velocity as narrows


* turbulence distal to stenosis


* Press.Grad.across the stenosis


* loss of pulsatility

Bernoulli's principle

Relationship between velocity & pressure in a moving fluid.


Simply stated sum of kinetic & pressure remains constant.

KNOW !!

Blood flows from high pressure to low pressure.

Pressure gradient increases when...

* flow increases


* resistance increases

Flow increases when ...

* pressure gradient increases


* resistance decreases

Hydrostatic pressure

Related to weight of blood pressing on a vessel measured above or below heart level.

Hydrostatic pressure is zero everywhere when patient is ...

Supine

Laying flat on back

2 reasons respiration affects venous flow

* venous is low pressure


* muscles alter thorax & abdomen

2 venous flows affected by breathing

* venous flow in legs


* venous return to the heart

Inspiration

* diaphragm down to abdomen


* thoracic pressure decreases


* abdominal pressure increases


* venous return increases


* venous flow in legs decrease

Expiration

* diaphragm upward to thorax


* thoracic pressure increases


* abdominal pressure decrease


* venous return decreases


* venous flow in legs increase

When venous flow in legs decrease ..

Venous return to heart increases

Inversely related

When venous flow in legs increase ...

Venous return to heart decreases

Inversely related