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FM1020 Physiology > The Circulatory System > Flashcards

The Circulatory System Flashcards

1
Q

What percentage of blood volume is in systemic circulation?

A

84%

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2
Q

How much of the blood is in the veins at one time?

A

64%

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3
Q

How much blood is in arteries at one time?

A

13%

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4
Q

How much blood is in systemic arterioles/capillaries at one time?

A

7%

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5
Q

How much blood is in the heart at one time?

A

7%

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6
Q

How much blood is in pulmonary vessels at one time?

A

9%

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7
Q

What is the tunica externa comprised of?

A

Connective tissue

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8
Q

What is the tunica media comprised of?

A

Smooth muscle

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9
Q

What is the tunica intima comprised of?

A

Layer of elastin
Basement membrane
Innermost simple squamous endothelium

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10
Q

What is microcirculation?

A

Arterioles, capillaries, venules

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11
Q

What are elastic arteries?

A

Conduits
Aorta and large arteries
Numerous layers of elastin fibers which expand when the pressure of the blood rises during systole and recoil when ventricles relax

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12
Q

What are muscular arteries and what is their makeup?

A

Resistance vessels
Are much less elastic and have a thicker layer of smooth muscle which regulates the diameter of the lumen

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13
Q

What are capillaries?

A

Exchange vessels
Smallest blood vessels
single layer of endothelium
Permits exchange of nutrients and waste between blood and tissue fluid

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14
Q

What is the diameter of capillaires?

A

5-10 microns

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15
Q

What are some other ways to describe veins?

A

Blood reservoirs
Capacitance vessels

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16
Q

What helps venous return?

A

Skeletal muscle pump and contraction of diaphragm assist

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17
Q

Where are the most vessels found?

A

Microcirculation

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18
Q

How many capillaries are there?

A

3 x 10^9

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19
Q

What vessels have the highest cross-sectional area?

A

Capillaries

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20
Q

Which vessels are wider and by how much: veins or arteries?

A

Veins have larger cross-sectional areas
~4 times wider than the corresponding arteries

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21
Q

What word can be used to describe veins high cross-sectional areas?

A

Highly distensible

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22
Q

What is the defintion of blood pressure?

A

Pressure of blood in the heart/circulatory system exerted outwards onto a unit area of the vessel wall

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23
Q

What is blood pressure measured in?

A

mmHg
Other units: cmH2O, atm, kPa

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24
Q

How do we calculate the pressure gradient?

A

P1 - P2 = delta P

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25
Q

What is the rate of blood flow directly proportionate to?

A

Delta P

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26
Q

What is the mean aortic pressure?

A

100mmHg

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27
Q

What is the mean venous pressure?

A

0mmHg

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28
Q

What kind of circulation is the pulmonary circulation?

A

Low resistance, Low pressure circulation

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29
Q

What is the blood pressure in the pulmonary artery?

A

20mmHg

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30
Q

What does resistance to blood flow cause?

A

Reduction in the rate of blood flow through vasculature

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31
Q

What is resistance to blood flow?

A

Vascular resistance
Friction between blood and walls of blood vessels
Friction from blood cells rubbing against each other (blood viscosity)

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32
Q

What is the rate of blood flow inversely proportional to?

A

Resistance

33
Q

Define Ohm’s Law

A

F = DELTA P / R
F = blood flow
R = resistance

34
Q

What factors does blood flow depend on?

A

Length of the blood vessel
Radius of the blood vessels
Viscosity of blood

35
Q

What is R directly proportional to?

A

Lη/r^4
Length of vessel*viscosity of blood/ radius of vessel^4

36
Q

What are the major regulators of blood flow?

A

Mean arterial pressure
Vascular blood vessel diameter - NB
Blood viscosity

37
Q

Where does more than half of all resistance to flow orginate?

A

Small arterioles

38
Q

What effect does the fourth power law have on resistance to blood flow?

A

Small changes in diameter result in large changes in resistance (256-fold)

39
Q

What is blood viscosity?

A

Cells suspended in blood plasma which exert friction; drag on each other and walls of blood vessels

40
Q

What is haematocrit?

A

% of total blood volume composed of cells

41
Q

What is the mean percentage of haematocrit in males?

A

42%

42
Q

What is the mean haematocrit percentage in females?

A

38%

43
Q

What is the viscosity of normal blood?

A

~ 3 times that of water (3)

44
Q

What condition may cause a haematocrit of 60?

A

Polycythaemia

45
Q

What can viscosity reach in the case of polycythaemia?

A

60

46
Q

What happens if viscosity is high?

A

Resistance increases and flow through blood vessels can be compromised

47
Q

What viscosity would you expect from a patient with severe anaemia?

A

1.5

48
Q

What does decreased resistance result in?

A

Increased peripheral blood flow
Increased venous return
Increased cardiac output

49
Q

What does hypoxia do?

A

Blood vessel dilation, increasing cardiac output

50
Q

What is ΔP?

A

Pressure drop that results from a given flow and resistance

51
Q

What is ΔP increased by?

A

Increase in flow or resistance

52
Q

What is blood vessel compliance?

A

Volume of blood that can be stored in a blood vessel for each mmHg pressure rise

53
Q

What is the equation for compliance?

A

Ca = ΔV/ΔP
compliance = distensibility*volume

54
Q

What is compliance closely related to?

A

Ability of a vessel to stretch or distend to accomadate larger volume of blood

55
Q

What is distensibility determined by?

A

Quantity of elastin fibers in vessel wall
Wall thickness

56
Q

When is blood flow in the vasculature continuous?

A

While ventricular ejection is pulsatile

57
Q

What is the property by which the vessels change a pulsatile ejection into a continuous blood flow called?

A

Hydraulic filter

58
Q

What is elastin content replaced by in older individuals?

A

Collagen

59
Q

Where does the increased pressure caused by stroke volume go?

A

Absorbed by arterial walls

60
Q

How do rigid and compliant arteries affect the workload of the heart?

A

Compliant reduce the workload
Rigid increase the workload

61
Q

What is systolic blood pressure?

A

120mmHg

62
Q

What is diastolic blood pressure?

A

80mmHg

63
Q

What are blood pressure measurements quoted as?

A

Systolic/diastolic pressure

64
Q

What is the best blood pressure?

A

120/80

65
Q

What is mean arterial pressure?

A

Diastolic pressure + 1/3 (systolic - diastolic pressure)

66
Q

What is hypertension?

A

Chronically elevated blood pressure

67
Q

What is the minimum value of systolic and diastolic pressure to be diagnosed with mild hypertension?

A

140 sys or 90 dia

68
Q

What are the two types of hypertension?

A

Essential
Secondary

69
Q

What is the most common form of hypertension?

A

Essential hypertension - accounts for 95% of cases

70
Q

What is the cause of essential hypertension?

A

Unclear, multifactorial such as diet or genetics

71
Q

What causes secondary hypertension?

A

Another condition such as renal disease

72
Q

How does renal disease cause secondary hypertension?

A

Chronically elevated salt and water reabsorption in the nephron will increase blood volume and chronically raise blood pressure

73
Q

What is the issue with hypertension?

A

Causes long-term damage to heart and kidneys and is a risk factor for heart attack and stroke

74
Q

How is afterload increased due to hypertension?

A

Ventricles must contract more forcefully to maintain an adequate stroke volume resulting in damage to myocardium

75
Q

What does damage to endothelial lining of arteries promote?

A

Formation of atherosclerotic plaques, increased risk of heart attack or stroke

76
Q

What is pulse pressure?

A

The difference between systolic pressure and diastolic pressure

77
Q

When is the dicrotic wace visible?

A

Diastole

78
Q

What is the dicrotic wave caused by?

A

recoil of blood from the closed aortic valve
Reflection of the systolic pressure wave back from small arteries in the lower body - NB
Measure of elasticity of one’s arteries

FM1020 Physiology (12 decks)

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