Flashcards in Chapter 18 Deck (80):
What is the study of blood moving through the circulatory system?
What indicates the volume of blood moving during a particular time?
flow or volume flow rate
What are the units for flow?
volume/time such as liters/min
What indicates the speed or swiftness of fluid moving from one location to another?
answers "how fast"
what are units for velocity?
distance divided by time such as cm/s
What are three basic forms of blood flow?
Which flow occurs when blood moves with a variable velocity?
pulsatile flow and phasic
Why does blood accelerate and decelerate in pulsatile flow?
b/c of cardiac contraction
Where does pulsatile flow appear?
in arterial circulation
Why does blood accelerate and decelerate in phasic flow?
due to respiration
Where is phasic flow appear?
in the venous circulation
What flow occurs when a fluid moves at a constant speed or velocity?
where does steady flow appear?
in the venous circulation when the individuals stops breathing for a brief moment.
What is laminar flow?
when the flow streamlines are aligned and parallel
What is laminar flow characterized by?
layers of blood that travel at individual speeds
What physiologic states does laminar flow and its two forms appear?
laminar flow is silent flow
What are two forms of laminar flow?
plug flow and parabolic flow
When does plug flow occur?
occurs hen all the layers and blood cells travel at the same velocity
explain 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.
What does the reynolds number predict?
if the flow is laminar or turbulent
What is the reynolds number for laminar flow?
less than 1,500
What is turbulent flow?
characterized by chaotic flow patterns in many different directions and at many speeds. the streamlines are often obliterated
associated with cardiovascular pathology
What is the patterns of turbulent flow?
small, hurricane like, swirling, rotational patterns. this is also called eddy current or a vortex
Where is turbulent flow profiles seen?
downstream from a significant stenosis in a vessel
What does turbulent flow convert?
converts flow energy into other form such as sound or vibration.
What is sound associated with turbulence called?
a murmur or a bruit
What is tissue vibration associated with turbulence is called?
What is a palpable murmur that you can feel with your fingertips?
What is reynolds number for turbulence flow?
greater than 2,000
What is energy gradient?
blood moves from regions of higher energy to lower energy.
What event provides energy to the circulating blood?
energy is imparted to blood by the contraction of the heart during systole
What are the forms of energy?
What is kinetic energy ?
associated with moving objects
What is kinetic energy determined by two factors?
an objects mass
the speed at which it moves
What is pressure energy?
a form of stored or potential energy.
What is potential energy?
a form of pressure energy and has the ability to perform work
What does pressure energy do?
a major form of energy for circulating blood and creates flow by overcoming resistance
What is gravitational energy?
also a form of stored or potential energy
associated with elevated objects
How is energy lost?
What describes the thickness of a fluid?
What is the units for viscosity?
Viscous energy loss n blood is determined by what?
What is hematocrit?
the percentage of blood made up of red blood cells.
What is a normal hematocrit value?
When does frictional loss occur?
occurs when flow energy is converted to heat as one object rubs against another.
What is an example of frictional loss?
blood sliding across vessels walls which creates heat
What relates to the tendency of a fluid to resist changes in its velocity?
What events cause loss of inertia?
velocity changes at a stenosis
When does velocity increases?
when a vessel narrows
max. velocity exits where the vessel is narrowest
Where does velocity decrease?
velocity decreases as blood flow out of the stenosis into a vessel segment of normal diameter
What is the narrowing in the lumen of a vessel?
What are the effects of a stenosis?
change in flow direction
increased velocity as vessel narrows
turbulence downstream from the stenosis
pressure gradient across the stenosis
loss of pulsatility
What is the stenosis flow converted to?
conversion of pulsatile flow patterns to steady flow
What is turbulence downstream from the stenosis called?
post stenotic turbulence
Where is the pressure in a stenosis lower?
pressure downstream from the stenosis is lower than the pressure upstream
Why does the post-stenotic pressure decrease?
results from the loss of energy as blood moves through the stenosis
What is Bernoulli Principle?
describes the relationship between velocity and pressure in a moving fluid
this principle also states that with a steady flow, the sum of all forms of energy is the same everywhere (so kinetic and pressure energy remains constant)
What is the formula for pressure gradient?
=flow x resistance
When does pressure gradient increases?
When does flow increase?
pressure gradient increases
What is Ohms law?
voltage= current x resistance
What are the units for resistance in a electrical system>
in the circulatory system, what is the name for resistance vessels?
What is hydrostatic pressure?
pressure related to the weight of blood pressing on a vessel measured at a height about or below heart level
What are the units for hydrostatic pressure?
mmHg, or units used to measure blood pressure
When supine, what is the hydrostatic pressure?
What is the formula for measured pressure for a standing patient?
measured pressure= circulatory pressure + hydrostatic pressure
In a standing patient, what is the hydrostatic pressure at the ankle?
in a standing patient, what is the hydrostatic pressure at the knee?
in a standing patient, what is the hydrostatic pressure at the waist?
in a standing patient, what is the hydrostatic pressure at the mid chest?
in a standing patient, what is the hydrostatic pressure at the top of head?
What parts of the body increase during inspiration?
head, arms and vena cava increase during inspiration
What parts of the body decrease during inspiration?
flow in the legs
What parts of the body decrease during expiration?
head, arms and vena cava all decrease during expiration
What parts of the body increase during expiration?
What are the breathing and venous flow for inspiration?
diaphragm moves downward toward the abdomen
thoracic pressure decreases
abdominal pressure increases
venous return to the heart increases
venous flow in the legs decreases
What are the breathing and venous flow for expiration?
diaphragm moves upward into thorax
thoracic pressure increases
abdominal pressure decreases
venous return to the heart decreases
venous low to the legs increases
What is the relationship between venous return to the heart and venous flow of the legs?