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SF3 > Hemodynamics and Circulation > Flashcards

Hemodynamics and Circulation Flashcards

1
Q

Blood vessels have ________ (open/closed) circulation.

A

Closed

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2
Q

What are the major functions of the circulatory system?

A
  • Transporting nutrients to the tissues
  • Carrying oxygen from the lungs to the rest of the body
  • Transporting waste products aray from the tissues
  • Transporting hormones
  • Distributing heat
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3
Q

What is the function of the aorta?

A

Transports blood to tissues under high pressure (100 mmHg)

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4
Q

What is the function of the superior and inferior vena cava?

A
  • Returns blood to the heart under low pressure
  • Serves as a reservoir of blood
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5
Q

What is the function of veins?

A

Conduit to the heart and reservoir

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6
Q

What is the function of the venules?

A

Blood collectors

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7
Q

What is the function of arteries?

A

To transport blood under high pressure

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8
Q

What is the function of arterioles?

A

Control conduits/gate keepers

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9
Q

Speed of blood flow in cm/sec is inversely related to ___________.

A

Cross sectional area

NOTE: Blood flow is slower in the arterial branches

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10
Q

Blood flow is the aorta is ______ cm/sec, while flow in capillaries is _____ cm/sec.

A

40;0.1

NOTE: Slow rate in capillaries allows for exchange

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11
Q

Circulation time is the time it takes a drop of blood to travel from ________ to ________.

A

Right atrium back to right atrium

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12
Q

Which component of the circulation has the largest total cross-sectional area? Which has the smallest?

A

Largest: Capillaries (2500 cm)

Smallest: Aorta (2.5 cm)

NOTE: CSA of capillaries is 1000 times higher than aorta

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13
Q

Rank the velocity of blood flow from component with the highest to component with the lowest.

A

Aorta> Arterioles> Small veins> Capilaries

*Velocity of blood flow= (Blood flow)/ (cross sectional area)

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14
Q

What are the units of the velocity of blood flow?

A

mm/sec

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15
Q

Largest pressure drop across the ___________ junction.

A

Arteriolar-capillary

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16
Q

Blood pressure is the highest in the ________.

A

Aorta

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17
Q

Blood pressure is defined as:

A

Pressure exerted by blood on walls of a vessel

*Caused by contraction of the ventricles

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18
Q

Pressure ___________ (falls/rises) steadily in systemic circulation with distance from left ventricle.

A

Falls

NOTE: BP is 35 mmHg entering the capillaries and 0 mmHg entering the right atrium

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19
Q

If decrease in blood volume is over _______%, BP drops.

A

10

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20
Q

Water rentention _________ (increases/decreases) blood pressure.

A

Increases

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21
Q

Compare the mean diameter of arteries and veins.

A

Mean diameter of veins (5 mm) is greater than the mean diameter of arteries (4mm).

NOTE: Arteries are thicker than veins

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22
Q

Korotkoff sounds

A

blood flowsounds that healthcare providers observe while taking blood pressure with a sphygmomanometer over the brachial artery in the antecubital fossa.

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23
Q

Korotkoff sounds are created by _______ blood flow through the compressed artery.

A

Pulsatile

NOTE: Blood flow is silent when the artery is no longer compressed

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24
Q

Pulse pressure

A

Systolic-Diastolic

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25
Q

Mean arterial pressure

A

Diastolic + 1/3 of Pulse Pressure

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26
Q

What physiological factors effect arterial blood pressure?

A

Cardiac output

Peripheral resistance

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27
Q

What physical factors effect arterial blood pressure?

A

Arterial blood volume

Arterial compliance

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28
Q

Hemodynamics

A

Physical factors governing blood flow within the ciculatory system

Factors: Flow, pressure, and resistance

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29
Q

Overall flow int eh circulation of an adult is ______ liters/min which is the cardiac output.

A

5

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30
Q

Blood usually flows in streamlines with each layer of blood remaining the smae distance from the wall, this type of flow is called __________.

A

Laminar flow

NOTE: When laminar flow occurs, the velocity of blood in the center of the vessel is greater than that toward the outer edge creating a parabolic profile

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31
Q

Parabolic flow profile

A

Concentric rings of blood flowing at different velocities; the farther away from the vessel wall, the faster the flow

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32
Q

Generally in the body, blood flow is laminar. However, under conditions of high flow, particularly in the __________, laminar flow can be disrupted and become turbulent.

A

Ascending aorta

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33
Q

Where does turbulent flow occur?

A

Ascending aorta

Large arteries at branch points

Diseased and narrowed (stenotic) arteries

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34
Q

What are some causes of turbulent blood flow?

A

High velocities

Sharp turns in the circulation

Rough surfaces in the circulation

Rapid narrowing of blood vessels

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35
Q

Reynolds number

A

An important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations.

Laminar flow: Low Reynold’s number

Turbulent flow: High Reynold’s number

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36
Q

At a critical velocity, Reynold’s number exceeds ________.

A

2000

37
Q

What are the major determinants of blood flow?

A
  • Pressure difference between the two ends of the vessel
  • Resistance of the vessel
38
Q

Ohm’s law

A
  • Blood flow through a blood vessel is determined by two factors
39
Q

In the systemic circulation the change in pressure is approximately _______

A

100 mmHg

*This is the aortic-right atrial pressure

40
Q

In the body the vascular beds of the various organ systems are arranged in _________.

A

Parallel

*This arrangement allows each organ to vary its flow independently in proportion to requirements

41
Q

Resistance is series is equal to…

A
42
Q

Resistance in parallel is equal to…

A

REMEMBER: This is how vascular beds of various organ systems are arranged to allow each organ to vary its flow independently in proportion to the requirements.

43
Q

_______ is a measure of the blood flow trhough a vessel for a given pressure difference.

A

Conductance= 1/ Resistance

*Units ml/min per mmHg

44
Q

Fourth Power Law

A

Small changes in vessel diameter markedly changes its conductnace

Resistance=1/ r4

45
Q

Poiseuille’s Law

A
  • Resistance to flow is directly proportional to viscosity of the blood and to the length to blood vessel
  • Resistance to flow is inversely proportional to the 4th power of the radius

NOTE:

  • η= Viscocity
  • r= radius
  • L= length of tube
46
Q

If you decrease the radius by 1/2, the resitance increases _______ fold.

A

16

NOTE: If you double radius of a tube by 2, the flow will increase 16 times

47
Q

The _______ (longer/shorter) the vessel, the greater the resistance to flow.

A

Longer

NOTE: There are 7 miles of new blood vessels for every pound of fat. Henceforth, obesity causes high blood pressure

48
Q

What can cause an increase in viscosity?

A
  • Dehydration
  • Polycythemia -a disease state in which the hematocrit (the volume percentage of red blood cells in the blood) is elevated.

REMEMBER: Increases in viscosity increase resistance

49
Q

What is blood viscosity?

A

Thickness measured by the ratio of red blood cells to plasma volume

50
Q

How is mean arterial pressure calculated?

A

Mean arterial pressure is a function of cardiac output and resistance in the arterioles

51
Q

How does arterial flow through the capillaries differ between systole and diastole?

A
  • Arterial blood flows through the capillaries throughout systole
  • Arterial blood continues to flow through the capillaries throughout diastole

NOTE: This only applies to compliant arteries

52
Q

How does blood flow through the capillaries change in rigid arteries?

A
  • A volume of blood equal to the entire stroke volume must flow through the capillaries during systole, because when the arteries are rigid virtually none of the stroke volume can be stored in the arteries.
  • Flow through the capillaries ceases during diastole because rigid arteries cannot recoil appreciably during diastole.
53
Q

What is vascular distensibility?

A
  • The ability of a blood vessel wall to expand and contract passively with changes in pressure.
  • The fractional increase in volume for each mmHg rise in pressure

NOTE: Veins are 8 times more distensible than arteries

54
Q

Arterial distensibility allows the arteries to accommodate ________ pressure.

A

Pulsatile

55
Q

Venous distensibility allow the venous system to act as a __________.

A

Reservoir

56
Q

________________ stimulation increases blood pressure in arteries and veins at a given volume to facilitate blood transfer through the circulation.

A

Sympathetic

57
Q

Blood pressure across the vascular networks

A
58
Q

Vein characteristics compared to arteries

A
  • Thinner walls
  • Highly distensible
  • Less muscle
  • Less elastic
  • Larger Diameter

NOTE: Veins do not have a pulse

59
Q

Approximately ____% of blood is found in veins.

A

64

60
Q

What role does the diaphragm play in blood flow?

A

Contraction of the diaphragm pumps blood into the right atrium:

  • Decreasing thoracic pressure
  • Increasing abdominal pressure

NOTE: During inhalation, pressure decreases in the thoracic cavity and increases in the abdominal cavity creating an upward “sucking” effect that pulls blood toward the heart.

61
Q

What is central venous pressure?

A

Pressure in the right atrium

NOTE: Right atrial pressure or central venous pressure is normally zero but can be as high as 20-30 mmHg.

62
Q

Abdominal pressures tend to increase venous pressures in the ___________.

A

Legs

63
Q

Increases in right atrial pressure causes blood to back up into the _______ system.

A

Venous

*This increases venous pressures

64
Q

What is the function fo microcirculation?

A
  • Important in the transport of nutrients to tissues
  • Site of waste product removal

*Over 10 billion capillaries with surface area of 500-700 square meters perform function of solute and fluid exchange

65
Q

Precapillary spincters

A

Provide control of perfusion through local capillary beds

66
Q

Metarterioles

A

Act as a bypass channel and regulate blood flow to capillary beds

67
Q

If precapillary sphinctors constrict, blood flow bypasses capillaries completely and flows through __________.

A

Metarterioles

*When precapillary sphincters are relaxed, blood flows through all capillaries in the bed

68
Q

What is the structure of capillary walls?

A
  • Composed of unicellular layer of endothelial cells surrounded by a basement membrane
69
Q

Solute and water move across capillary wall via _______ or by ____________.

A

Intercellular cleft; Plasmalemma vesicles

70
Q

What is the diameter of capillaries?

A

4 to 9 microns

71
Q

How do solutes and fluids cross the capillary wall?

A
  • Lipid solube: Diffuse directly through cell membrane
  • Lipid insoluble: Cross capillary walls via intercellular clefts
72
Q

How does molecular size affect passage of molecules across the capillary wall?

A
  • The width of capillary intercellular slit pores is 6 to 7 nanometers
  • The permeability of the capillary pores for different substances varies according to their molecular diameters
  • The capillaries in different tissues have extreme differences in their permeabilities
73
Q

Relative Permeability of Muscle Capillary

A
74
Q

Two major types of solid structures in interstitium are _____ and _________.

A

Collagen fibers and proteoglycan

75
Q

Almost all fluid in interstitium is in the form of _______.

A

Gel

*There is very little free fluid under normal conditions

76
Q

What are the determinants of net fluid movement across capillaries?

A

The forces that tend to move fluid out from the capillaries are the capillary hydrostatic pressure(estimated to about 20 mm Hg), the interstitial-fluidosmotic pressure (about 8 mm Hg) and the interstitial-fluid hydrostatic pressure, which is normally negative

77
Q

Net fluid movement across capillaries equation

A

Pc= Capillary pressure

Pif= Interstitial fluid pressure

πp= Plasma colloid osmotic pressure

πif= Interstital fluid colloid osmotic pressure

78
Q

Increase in _________ pressure forces fluid out of the capillaries.

A

Hydrostatic

79
Q

Decrease of _________ pressure of proteins within the capillary pulls fluid into the capillary.

A

Colloid osmotic

80
Q

About ______ 2 L/day collected by lymph vessels.

A

2

NOTE: The excess water and solutes that filter out of the capillary are picked u[ by the lymph vessels and returned to the circulation

81
Q

The lymphatic system is a major route for absorption of nutrients from __________.

A

The GI tract

NOTE: The lymphatic system is also important in the immune system and preventing edema

82
Q

________ % of filtered fluid is reabsorbed on the venous end.

A

90

*The remaining 90% is returned to circulation via lymphatics

83
Q

How do changes in interstitial hydrostatic pressure affect lymph flow?

A

An increase in intersitial fluid hyrostatic fluid results in a increase in lymph flow?

84
Q

What are the causes of edema?

A
  • Increased hydrostatic blood pressure
  • Decreased blood osmotic pressure
  • Lymphatic capillary blockage
  • Leaking capillary wall
85
Q

What factors can lead to increase in hydrostatic blood pressure?

A
  • Heart failure (left or right)
  • Excess fluid in the blood
86
Q

What factors can lead to decrease in blood osmotic pressure?

A

Liver, kidney diseases

87
Q

What factors can lead to lymphatic capillary blockage?

A

Breast cancer surgery

Elephantiasis

88
Q

What factors can lead to leaking capillary wall?

A

Histamine release during allergic reaction

Burn injuries

SF3 (15 decks)

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