Lecture 20 Flashcards
Plug flow is at ________ to tubes
Enterance
Plug flow blood moves as
A unit
In Plug flow there is the same ______ across the vessel
Speed
Two types of flow
Laminar
Turbulent (non-laminar)
3 types of laminar flow
Plug flow
Parabolic
Disturbed flow
Parabolic/ laminar happens when
After entering the straight tube
The fastest speed in parabolic is where
The center of the tube
During doppler we assess where in the tube
The centre
The slowest speed in parabolic is where
Tube wall
Average flow speed in parabolic is
Half the fastest speed
Disturbed flow occurs at a
Stenosis or bifurcation
Disturbed flow is still _______ flow but streamlines are not ____
Laminar
Straight
Disturbed flow is non- _____
Parabolic
Turbulent flow usually occurs after a
Significant stenosis
Turbulent flow can also be called what 4 things
Chaotic, multidirectional, multispeed flow, non laminar
Turbulent flow is related to
Eddies —> flow in circles but still with forward net flow
With turbulent flow physician may hear a
“Bruit”
Often main reason for the ultrasound
Turbulent flow depends on
Reynolds number
Critical reynolds number =
2000 for blood
Flow must surpass ________ to cause turbulent flow
a critical reynolds #
Reynolds number equation
Re= pvd/n
, p = density of fluid , v = velocity of fluid , d = diameter of pipe , n = viscosity , Re= reynolds number
What is a stenosis
Partial blockage
Occlusion
Complete blockage
In compliant vessels we observe
Added forward flow and reversal of flow
Compliance is
Expansion and contraction of non-rigid vessels during systole and diastole
Added forward flw aka
Windkessel effect
Systole
The vessel expands
Diastole
Vessel contracts, resulting in extended flow without driving pressure from heart
Flow reversal occurs during
Diastole
Blood doesn tflow back into the heart becuase
Valve closes
In distal circulation, in some locations, when pressure decreases and vessel contracts there will be ____
Reversal of flow
There are no valves present to stop it
At the stenosis the speed goes
Up
Why does the speed go up in stenosis
What is the concept called
To keep volumetric flow rate (Q) constant at all 3 regions (before, at and after)
Continuity rule
Laminar flow is flow in which
Layers of fluid slide over eachother in straight lines
