Chapter 18 Flashcards
(122 cards)
1
Q
the study of blood moving
through the circulatory system
A
Hemodynamics
2
Q
_ indicates the volume of
blood moving during a particular time
A
Flow (volume flow rate)
3
Q
_ answers the question: How much?
A
Flow
4
Q
Units for flow
A
voulme/time (L/min)
5
Q
_ the speed or swiftness of a fluid moving
from one location to another
A
Velocity
6
Q
Velocity answer the question:
A
How fast?
7
Q
Units for velocity
A
distance/time (cm/s)
8
Q
Flow patterns in normal vessels are _ and vary with _
A
extremely complex
location, time within the heart cycle, and exercise
9
Q
Pathologic conditions create _
A
even more diversity in flow patterns
10
Q
Three basic forms of blood flow:
A
Pulsatile
Phasic
Steady
11
Q
_ flow – when blood moves at a variable
velocity. Blood accelerates and decelerates as a
result of cardiac contraction, commonly appears in
arterial circulation
A
Pulsatile
12
Q
_ flow – blood moves with a variable velocity.
Blood accelerates and decelerates as a result of
respiration, often appears in venous circulation
A
Phasic
13
Q
_ flow – occurs when a fluid moves at a constant
speed or velocity. Present in the venous circulation
when individuals stop breathing for a brief moment.
A
Steady
14
Q
_ flow is when the
flow streamlines are
aligned and parallel.
A
Laminar
15
Q
_ flow is characterized by layers of
blood that travel at
individual speeds
A
laminar
16
Q
Laminar flow is commonly found in _
A
normal physiologic states
17
Q
2 forms of laminar flow
A
Plug
Parabolic
18
Q
bullet-shaped profile. Velocity is highest in the center of the lumen, and gradually decreases to its minimum at the vessel wall.
A
Parabolic flow
19
Q
Plug flow
A
all of the layers and
blood cells travel at the same
velocity
20
Q
Plug flow and parabolic flow are both associated with
A
normal physiology
21
Q
Silent flow
A
laminar flow
22
Q
Turbulent flow is
characterized by
A
chaotic flow patterns in many different directions at many different speeds. The streamlines are often obliterated.
23
Q
small,
hurricane-like, swirling,
rotational patterns that
appear in turbulent flow
A
Eddy/vortex
24
Q
Turbulent flow is often associated with
A
cardiovascular pathology
and elevated blood
velocities
25
_ flow may be seen downstream from a stenosis in a vessel
Turbulent
26
Turbulent flow converts _ into _
flow energy
| other forms such as sound or vibration
27
sound associated with
| turbulence
Murmur or bruit
28
tissue vibration associated with
turbulence, also described as a palpable
murmur
Thrill
29
The Reynold's number is _
a unitless number that
| predicts whether flow is laminar or turbulent.
30
Vessels with comparable Reynold’s numbers
| exhibit
similar flow characteristics
31
Reynold’s numbers above 2000 indicate
turbulent flow
32
Reynold’s numbers under 1500 will have _ flow
laminar
33
Blood moves from regions of _ to _
higher energy
| lower energy
34
energy is imparted to blood by _
the contraction of
| the heart during systole.
35
Forms of energy associated with blood:
Kinetic
Pressure
gravitational
36
_ energy: Associated with a moving object
Kinetic
37
Kinetic energy is determined by 2 factors:
An object’s mass
| The speed at which it moves
38
Heavy/quickly moving objects have _ kinetic
| energy
high
39
Light/slowly moving objects have _ kinetic
| energy
low
40
Pressure Energy
A form of stored or potential energy. It is a major form of energy for circulating blood and creates flow by overcoming resistance
41
Potential energy has
he ability to perform work
42
Gravitational energy
A form of stored or potenetial energy that is associated with any elevated object.
43
All elevated objects have _
stored energy that can perform work
44
As blood flows through the circulation, energy is
| lost in 3 ways:
Viscous loss
Frictional loss
Inertial loss
45
Viscosity
the thickness of a fluid
46
The thicker the fluid the _ viscous it is
more
47
Viscosity is measured in units of
poise
48
More energy is lost with movement of _ viscosity fluids
high
49
Viscous loss is associated wit
blood overcoming its internal
| stickiness
50
Hematocrit
the percentage of blood made up of red
| blood cells.
51
Normal hematocrirt
aprrox. 45%
52
Viscous energy loss is determined b
Hematocrit
53
Frictional losses occur when
low energy is
converted to heat as one object rubs against
another
54
exxample of frictional loss:
Blood sliding across vessel walls creates heat
55
Inertial Energy Loss: Energy is lost when
the speed of a fluid changes, regardless
| of whether the fluid accelerates or decelerates
56
tendency of a fluid to resist changes in velocity
Inertia
57
Inertial energy loss occurs during three events:
Pulsatile flow
Phasic flow
Velocity changes at a stenosis (maximum velocity exists where
the vessel is narrowest and decreases as the blood flows out of
the stenosis into a vessel segment of normal diameter)
58
a narrowing in the lumen of a vessel
Stenosis
59
Stenosis may have these effects on blood flow:
[] Changes in direction as blood flows into and out of the narrow portion of the vessel
Increased velocity within the stenosis (Velocity is the highest where the vessel is the narrowest)
Turbulence downstream from the stenosis (post-stenotic turbulance)
Eddy currents, vortices, may have bruit, murmur or thrill
Pressure gradient across the stenosis (pressure downstream is lower than the pressure upstream)
Conversion of pulsatile flow patterns to steady flow
60
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
61
Describes the relationship between velocity and
| pressure in a moving fluid
Bernoullis principle
62
Bernoullis principle s derived from
the principle of conservation of energy
63
With steady flow, the sum of all forms of energy is _
the same everywhere
64
Bernouliis principle: the sum of _ energy and _ energy remains constant
kinetic and pressure
65
Bernoulli’s Principle: Where kinetic energy is the highest,
| pressure energy will be _
the lowest and vise versa
66
Pressure gradient =
flow x resistance
67
Study of blood flow is complex due to
the elastic nature of
blood vessels, composition of blood, and pulsatile nature of
heart pumping
68
Pressure gradient increases with _
an increase in flow or resistance
69
Flow increases with
an increase in pressure gradient or a
| decrease in resistance
70
Ohms law
Voltage = current x resistance
71
Electrical resistance is reported
ohms
72
Resistance vessels are called
arterioles
73
Fluids: pressure
Electricity:
voltage
74
Fluids: flow
Electricity:
current
75
Fluids: resistance
Electricity:
resistance (ohms)
76
_ are thin-walled and
| collapsible
veins
77
During normal function,
veins have a _ pressure
and are _
expanded (_ shaped)
low
only partly
hourglass
78
Veins are _ resistance vessels
low
79
When venous flow increases
with exercise, the cross-
sectional shape of a vein
changes from_, to _, and then to _
hourglass
oval
round
80
As veins become more round,
| the resistance to flow_ which increases _
decreases
| outflow toward the heart
81
Hydrostatic pressure
Pressure related to the weight of blood pressing
on a vessel measured at a height above or
below heart level
82
Units for hydrostatic pressure
mmHg
83
Hydrostatic pressure is important when _
measuring blood pressure
84
Pressures are accurately assessed when the
| measurement is made at
heart level
85
Measurement is too _ if measurement is made
| below heart
high
86
Measurement is too _ if measurement is made
| above heart
low
87
When a person is _, all
parts of the body are at the
same level as the heart
supine
88
When a person is supine hydrostatic pressure is _
zero everywhere
89
A pressure measured
anywhere on a supine patient
accurately represents_
true circulatory pressure
90
Hydrostatic Pressure- standing: At heart level, the hydrostatic pressure is _
zero
91
Hydrostatic pressure- standing: At locations below heart level, hydrostatic
pressure is _. The measured pressure will be _
positive
| higher than true circulatory pressure
92
Hydrostatic pressure- standing: At locations above the heart, hydrostatic pressure
is _. The measured pressure will be _
negative
| lower than the true circulatory pressure
93
Hydrostatic pressure- standing: measured pressure=
circulatory pressure + hydrostatic pressure
94
hydrostatic pressure @ ankle
100 mmHg
95
hydrostatic pressure @ knee
75 mmHg
96
hydrostatic pressure @ waist
50 mmHg
97
hydrostatic pressure @ mid chest
0 mmHg
98
hydrostatic pressure @ top of head
-30 mmHg
99
n normal individuals, respiration affects venous
| flow for two reasons:
The venous system is low pressure
| Muscles responsible for respiration alter pressures in the thorax and the abdomen
100
Breathing affects two venous flows:
Venous flow in the legs
| Venous return to the heart (compromises venous flow from the head, arms, and flow from the IVC to the heart)
101
_ is the
muscle responsible for
breathing
the diaphragm
102
the diaphragm is located between _ and _
thorax and abdomen
103
During inspiration, the
| diaphragm moves
downward
104
During inspiration, the chest cavity _, creating _ in the chest
expands
| negative pressure
105
Negative thoracic pressure
| creates
suction that increases
| venous return to the heart
106
Venous flow from the head,
arms, and vena cava _
during inspiration
increases
107
During inspiration, the
| diaphragm also
presses into the abdomen
108
inspiration: Abdominal compression
| increases _
abdominal pressure
109
Inspiration: venous flow in the legs _
decreases
110
During expiration, the
| diaphragm moves _, _pressure in the chest
upward
| increasing
111
Expiration: Increased thoracic pressure
__(increases or reduces) venous return to the
heart.
reduces
112
Venous flow from the head,
arms, and vena cava all
_ during expiration.
decrease
113
During expiration, the
diaphragm _
the abdomen.
decompresses
114
Expiration: _ in abdominal pressure
decrease
115
Expiration: _ in venous flow from the legs
increase
116
```
Inspiration:
Diaphragm moves _
Thoracic pressure _
Abdominal pressure _
Venous return to the heart _
Venous flow in legs _
```
```
downward toward the abdomen
decreases
increases
increases
decreases
```
117
```
Expiration:
Diaphragm moves _
Thoracic pressure _
Abdominal pressure _
Venous return to the heart _
Venous flow in legs _
```
```
upward into the thorax
increases
decreases
decreases
increases
```
118
Venous flow in the legs correlates with
movement of the diaphragm.
119
Downward movement of diaphragm =
decreases
| venous flow in the legs
120
Upward movement of diaphragm =
ncreases
| venous flow in the legs
121
Changes in venous return to the heart are _ to those of venous flow in the legs
opposite
122
```
Valsalva _ (increases or decreases_ pressure in the thorax and
reduces all venous flows
```
increases
