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Flashcards in Chapter 18 Deck (80):
1

What is the study of blood moving through the circulatory system?

hemodynamics

2

What indicates the volume of blood moving during a particular time?

flow or volume flow rate

3

What are the units for flow?

volume/time such as liters/min

4

What indicates the speed or swiftness of fluid moving from one location to another?

velocity
answers "how fast"

5

what are units for velocity?

distance divided by time such as cm/s

6

What are three basic forms of blood flow?

pulsatile
phasic
steady

7

Which flow occurs when blood moves with a variable velocity?

pulsatile flow and phasic

8

Why does blood accelerate and decelerate in pulsatile flow?

b/c of cardiac contraction

9

Where does pulsatile flow appear?

in arterial circulation

10

Why does blood accelerate and decelerate in phasic flow?

due to respiration

11

Where is phasic flow appear?

in the venous circulation

12

What flow occurs when a fluid moves at a constant speed or velocity?

steady flow

13

where does steady flow appear?

in the venous circulation when the individuals stops breathing for a brief moment.

14

What is laminar flow?

when the flow streamlines are aligned and parallel

15

What is laminar flow characterized by?

layers of blood that travel at individual speeds

16

What physiologic states does laminar flow and its two forms appear?

normal
laminar flow is silent flow

17

What are two forms of laminar flow?

plug flow and parabolic flow

18

When does plug flow occur?

occurs hen all the layers and blood cells travel at the same velocity

19

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.

20

What does the reynolds number predict?

if the flow is laminar or turbulent

21

What is the reynolds number for laminar flow?

less than 1,500

22

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

23

What is the patterns of turbulent flow?

small, hurricane like, swirling, rotational patterns. this is also called eddy current or a vortex

24

Where is turbulent flow profiles seen?

downstream from a significant stenosis in a vessel

25

What does turbulent flow convert?

converts flow energy into other form such as sound or vibration.

26

What is sound associated with turbulence called?

a murmur or a bruit

27

What is tissue vibration associated with turbulence is called?

a thrill

28

What is a palpable murmur that you can feel with your fingertips?

a thrill

29

What is reynolds number for turbulence flow?

greater than 2,000

30

What is energy gradient?

blood moves from regions of higher energy to lower energy.

31

What event provides energy to the circulating blood?

energy is imparted to blood by the contraction of the heart during systole

32

What are the forms of energy?

kinetic
pressure
gravitational

33

What is kinetic energy ?

associated with moving objects

34

What is kinetic energy determined by two factors?

an objects mass
the speed at which it moves

35

What is pressure energy?

a form of stored or potential energy.

36

What is potential energy?

a form of pressure energy and has the ability to perform work

37

What does pressure energy do?

a major form of energy for circulating blood and creates flow by overcoming resistance

38

What is gravitational energy?

also a form of stored or potential energy
associated with elevated objects

39

How is energy lost?

viscous loss
frictional loss
inertial loss

40

What describes the thickness of a fluid?

viscosity

41

What is the units for viscosity?

poise

42

Viscous energy loss n blood is determined by what?

hematocrit

43

What is hematocrit?

the percentage of blood made up of red blood cells.

44

What is a normal hematocrit value?

45%

45

When does frictional loss occur?

occurs when flow energy is converted to heat as one object rubs against another.

46

What is an example of frictional loss?

blood sliding across vessels walls which creates heat

47

What relates to the tendency of a fluid to resist changes in its velocity?

inertia

48

What events cause loss of inertia?

pulsatile flow
phasic flow
velocity changes at a stenosis

49

When does velocity increases?

when a vessel narrows
max. velocity exits where the vessel is narrowest

50

Where does velocity decrease?

velocity decreases as blood flow out of the stenosis into a vessel segment of normal diameter

51

What is the narrowing in the lumen of a vessel?

stenosis

52

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

53

What is the stenosis flow converted to?

conversion of pulsatile flow patterns to steady flow

54

What is turbulence downstream from the stenosis called?

post stenotic turbulence

55

Where is the pressure in a stenosis lower?

pressure downstream from the stenosis is lower than the pressure upstream

56

Why does the post-stenotic pressure decrease?

results from the loss of energy as blood moves through the stenosis

57

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)

58

What is the formula for pressure gradient?

=flow x resistance

59

When does pressure gradient increases?

flow increases
resistance increases

60

When does flow increase?

pressure gradient increases
resistance decreases

61

What is Ohms law?

voltage= current x resistance

62

What are the units for resistance in a electrical system>

ohms

63

in the circulatory system, what is the name for resistance vessels?

arterioles

64

What is hydrostatic pressure?

pressure related to the weight of blood pressing on a vessel measured at a height about or below heart level

65

What are the units for hydrostatic pressure?

mmHg, or units used to measure blood pressure

66

When supine, what is the hydrostatic pressure?

zero

67

What is the formula for measured pressure for a standing patient?

measured pressure= circulatory pressure + hydrostatic pressure

68

In a standing patient, what is the hydrostatic pressure at the ankle?

100 mmHg

69

in a standing patient, what is the hydrostatic pressure at the knee?

75 mmHg

70

in a standing patient, what is the hydrostatic pressure at the waist?

50 mmHg

71

in a standing patient, what is the hydrostatic pressure at the mid chest?

zero

72

in a standing patient, what is the hydrostatic pressure at the top of head?

-30 mmHg

73

What parts of the body increase during inspiration?

head, arms and vena cava increase during inspiration

74

What parts of the body decrease during inspiration?

flow in the legs

75

What parts of the body decrease during expiration?

head, arms and vena cava all decrease during expiration

76

What parts of the body increase during expiration?

legs

77

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

78

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

79

What is the relationship between venous return to the heart and venous flow of the legs?

inversely

80

what is the relationship between venous flow in the legs with the movement of the diaphragm?

directly