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Vascular Sonography > Hemodynamics of Vascular Disease > Flashcards

Hemodynamics of Vascular Disease Flashcards

1
Q

What is blood flow influenced by

A
  1. Heart influences the strength and amount of ejected blood
  2. Elastic arteries store energy during systole and maintain blood flow during diastole
  3. Muscular arteries maintain tone
  4. Arterioles, capillaries and venules supply blood to different organs
  5. veins ensure adequate return of blood to the heart
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2
Q

what must be present for blood flow to occur between any two points in the circulatory system

A

Energy difference between these two points

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3
Q

what is the difference in energy levels usually caused by?

A

Blood pressure

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4
Q

what is continually lost because of friction between the layers of flowing blood

A

energy

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5
Q

Both ______ and ______decrease as the red blood cells transit from the arterial to the venous system

A

Pressure and kinetic energy

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6
Q

What does generated arterial pressure do?

A

Forces blood to move from the arterial system into the venous system and maintains the arterial pressure and the energy difference needed for blood to keep flowing

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7
Q

where is a balance of blood mainatined

A

Arterial reservoir

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8
Q

blood flow to all the body tissues is adjudged

A

According to the tissues particular needs at a given time

Achieved by vasoconstriction

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9
Q

what is the main form of blood stored in flowing blood

A

Potential energy due to the pressure of distending the vessels

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10
Q

Some energy stored in blood is also____

A

Kinetic energy

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11
Q

Kinetic energy of blood is proportional to what?

A

its density (stable in normal circumstances)

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12
Q

Kinetic energy is proportional to the square of

A

Its velocity

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13
Q

As artery lumen increases

A

Kinetic energy is converted back into pressure (potential energy) as velocity decreases

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14
Q

Narrowed artery lumen

A

Potential energy is converted back into kinetic energy

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15
Q

blood flow is said to be what?

A

Laminar

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16
Q

Loss of energy is due to

A

Friction

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17
Q

Amount of friction and energy loss

A

Largely determined by the dimensions of the vessels

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18
Q

Decrease in radius by 10%

A

Decrease the volume flow in a rube by about 35%

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19
Q

Poiseuille’s law

A

Applies to constant laminar flow of a simple fluid in a rigid tube of a uniform diameter

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20
Q

Vessels in a series

A

overall resistance is equal to the sum of the resistances of the individual vessels

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21
Q

where do alterations in blood flow profiles occur?

A

Curves, bifurcations, any branch point and at stenic lesions

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22
Q

Site of boundary layer seperation

A

Transition zone where the lamina has zero velocity, classically at the carotid artery bifurcation

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23
Q

what does the vascular system consist of?

A

Heart, arteries, arterioles, capillaries, venules, veins

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24
Q

what occurs across the capillary walls

A

exchange of gases, nutrients and waste products

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25
Q

pulmonary circulation

A

right side of the heart pumps blood through pulmonary vessels, through the lungs for oxygenation and back to the left side of the heart

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26
Q

Systemic circulation

A

Pumps blood from the left side of the heart through vessels supplying either the head and arms or the lower body and back to the right side of the heart

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27
Q

Heart

A

Propels blood through the system

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28
Q

Arteries

A

Series of vessels efferent from the heart that become smaller and smaller as they branch into various organs

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29
Q

Capillaires

A

Smallest vessels, site of exchange between blood and tissue

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30
Q

Microvasculature bed

A

complex network of thin, anastomosing tubules formed by capillaries

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31
Q

Veins

A

Convergence of venules into a system of larger channels that continue enlarging as they approach the heart

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32
Q

what occurs in pulmonary circulation

A

blood is oxygenated by the lungs

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33
Q

what occurs in systemic circulation

A

Blood brings nutrients and removes waste in tissues throughout the body

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34
Q

What are organs with high metabolic rates

A

Liver
Spleen
Kidneys

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35
Q

what kind of vascular beds do high metabolic rate organs have?

A

Low resistance vascular beds

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36
Q

what are organs with low metabolic rates

A

Stomach
Small intestine
Muscle

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37
Q

what kind of vascular beds do low metabolic rate organs have?

A

High resistance vascular beds

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38
Q

what are the three layers of vessel walls?

A

Tunica intima
Tunica media
Tunica adventitia

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39
Q

Tunica Intima

A

Innermost layer

Consists of endothelial cell lining with connective tissue beneath

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40
Q

Tunica Media

A

Middle layer
Thickest component
Composed mainly of smooth muscle
Varies in the amounts of elastic fibers and collagen

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41
Q

Tunica Adventitia

A

Outermost layer
Composed of connective tissue, nerve fibers, and small vessel capillaries
In contact with surrounding tissue

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42
Q

what is the size of large conducting arteries

A

2.5-1cm

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43
Q

what are large arteries composed of?

A

Elastic arteries with less smooth muscle

Aorta and its largest branches

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44
Q

what are medium and small sized arteries composed of?

A

Well developed smooth muscle layers

Includes all arteries except aorta and major branches

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45
Q

what is the size of medium and small-sized arteries

A

Approximately 1 -0.3mm in diameter

46
Q

What is the size of arterioles

A

03.mm - 10 µm

47
Q

what do arterioles do?

A

Stopcocks“ of the vascular system

Circular smooth muscle layers control contraction and resistance

48
Q

what is minute by minute flow into the capillary bed determined by?

A

arteriole diameter

49
Q

are veins more or less muscular?

A

less muscular

50
Q

are veins more or less thick then arteries

A

Walls are thinner than arteries

51
Q

what are the walls of venules composed of?

A

Connective tissue

52
Q

size of venules

A

8 - 100 µm

53
Q

Size of medium veins

A

Diameters from 1 to 10 mm

54
Q

what do medium veins include

A

Includes all veins except portal vein and vena cava and main branches
Have a thin tunica media

55
Q

what are large veins

A

Include portal vein, superior and inferior vena cava (IVC), and main branches
Thick adventitial layer with fibrous and elastic tissues

56
Q

what do venous valves prevent?

A

Retrograde movement of blood

57
Q

what are venous valves

A

Bicuspid inward projections of tunica intima

58
Q

What is the sinus

A

Enlarged area behind leaflets

59
Q

where are valves most numerus

A

Lower extremities

60
Q

Where are valves absent?

A

thorax and abdomen

61
Q

what is the smallest vessel in the body?

A

Capillaries

62
Q

what is the wall of the capillary composed of?

A

Walls composed primarily of a layer of endothelial cells with small amount of basement membrane
Primary place where nutrient exchange occurs

63
Q

total energy remains what?

A

Constant-conserved over time

64
Q

Energy….

A

can be neither created nor destroyed; rather transforms from one form to another

65
Q

what is total fluid energy made up of?

A

Potential and kinetic energy

66
Q

Potential energy

A

Stored or resting energy
Represented by the intravascular pressure
Supplied by the contraction of the heart

67
Q

what stores potential energy

A

Contraction of the heart

68
Q

Kinetic energy

A

Energy of work or motion

Represented by the velocity of moving blood

69
Q

how does blood move

A

Moves from an area of high energy (pressure) to an area of lower energy (pressure)

70
Q

Circulatory system is what kind of system?

A

Closed system

71
Q

what must there be for blood to move

A

Energy gradient

72
Q

what is the driving force behind fluid flow?

A

Pressure

73
Q

The greater the pressure difference

A

The greater the flow rate (Directly proportional)

74
Q

Equal pressure

A

No flow

75
Q

Korotkoff sounds

A

soft ticking while measuring blood pressure

76
Q

Continuity Rule

A

Blood is neither created nor destroyed as it flows through a vessel
What goes in must come out

77
Q

Volumetric flow rate must be what?

A

Constant proximal, within and distal to a change in vessel diameter

78
Q

what does the continuity rule mean?

A

Same volume proximally moves distally to a narrower area and therefore will necessitate a fast velocity to get through the vessel.

79
Q

Velcoity

A

rate of movement with respect to time (centimeters per second)

80
Q

Volume Flow

A

the volume of something moved per unit time (milliliters per second)

81
Q

what is the velocity formula?

A

v=Q/A

V=Velocity, Q=Volume, A=Area

82
Q

what occurs with stenosis (Narrowing)

A

VELOCITY must increase to maintain volume flow

83
Q

Area is _______to velocity

A

Indirectly Proportional

84
Q

As total cross sectional area increases

A

Blood velocity decreases

85
Q

what does Poiseuille’s Law define

A

Defines the pressure/flow relationships in the vascular system

86
Q

Poiseuille’s law: pressure difference

A

If pressure difference or the diameter of the tube increases, flow rate increases

87
Q

Poiseuille’s law: Viscoity

A

If viscosity or the length of the tube increases, flow rate decreases

88
Q

what is viscosity

A

Property of a fluid that resists the force tending to cause fluid to flow
The friction that exists between bordering layers of fluid
Creates energy “losses” in the vascular system (conversion of friction to heat)

89
Q

what is resistance equal to?

A

Resistance is equal to the pressure drop divided by flow

90
Q

How can resistance be expressed?

A

In the circulatory system, blood vessel length is virtually constant as is blood viscosity
Changes in resistance are due to changes in vessel radius

91
Q

what causes changes in resistance

A

Due to changes in vessel radius

92
Q

Series resistance

A

The total resistance of the entire system equals the sum of the individual resistances

93
Q

what will multiple stenosis’s do?

A

Multiple stenosis’ along the same blood vessel will increase the total resistance

94
Q

Parallel resistance

A

The reciprocal of the total resistance is equal to the sum of the reciprocals of the individual resistances

95
Q

what occurs with more parallel elements in a network

A

the lower the overall resistance of the network

96
Q

Plug Flow

A

The speed of the fluid is essentially constant across the tube
As flow enters a vessel, streamlines move in approximately the same velocity

97
Q

Laminar flow

A

Streamlines are straight and parallel to each other

Flow speed is maximum at the center of the tube and minimum or zero at the tube’s walls

98
Q

what occurs with laminar flow

A

Successive layers of fluid slide on each other with relative motion.

99
Q

what is blood flow

A

Laminar

100
Q

Parabolic flow

A

A form of laminar flow

The average flow speed across the vessel is equal to one half the maximum flow speed (center)

101
Q

where is parabolic flow often seen?

A

Thoracic and abdominal aorta

102
Q

Disturbed flow

A

A form of laminar flow

Occurs when the parallel streamlines are altered from their straight line form

Occurs in the region of a stenosis or at a bifurcation

103
Q

Turbulent Flow

A

Non-laminar flow with random and chaotic speeds and directions
Forward net flow is still maintained
Greater pressure is required to move fluid under turbulent conditions
Turbulence can be defined by “Reynolds number”

104
Q

when can turbulence occur

A

Transition from high flow speed in a narrow channel to slow flow in a broad stream

105
Q

Inertia

A

Is the tendency of a body at rest to stay at rest or a body in motion to stay in motion unless acted upon by an outside force.

106
Q

what is Reynolds number

A

likelihood of turbulence

107
Q

What is Reynolds number directly proportional to?

A
  • velocity of blood
  • density of blood
  • radius of blood vessel
108
Q

what is Reynolds inversely proportional to?

A

-viscosity of blood

109
Q

when is turbulence likely to develop?

A

Reynolds number above 2000

110
Q

what does turbulence mainly depend on?

A

velocity and vessel radius

111
Q

as blood flows through a stenosis, what occurs?

A

velocity increases

112
Q

what occurs after a stenosis

A

Turbulence

Vascular Sonography (10 decks)

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