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Life support > Arteries, arterioles and veins > Flashcards

Arteries, arterioles and veins Flashcards

1
Q

What is haemodynamics?

A

relationship between blood flow, blood pressure and
resistance to flow

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2
Q

What is work?

A

Expend energy to produce
cardiac contraction which creates
Isovolumetric contraction
and ejection

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3
Q

What is pressure?

A

Generated to drive
bulk/convection transport

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4
Q

What is compliance?

A

Large artery stretch

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5
Q

Where is resistance generated?

A

Arterioles

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6
Q

Where is blood flow slowed down?

A

blood is slowed down in capillaries

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7
Q

What are the three patterns of blood flow?

A
  1. Laminar
  2. Turbulent
  3. Bolus
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8
Q

Where is laminar flow mostly found?

A

Most arteries, arterioles, venules,
veins

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9
Q

How can laminar flow be described and what is the behaviour like for RBC transport?

A

Concentric shells
Zero velocity at walls
(molecular interactions
between blood and wall)
Maximum velocity at centre
Move RBCs towards centre
Speeds up blood flow
through narrow vessels

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10
Q

Where is turbulent blood flow found?

A

Ventricles (mixing), aorta (peak flow),
Atheroma (bruits)

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11
Q

How can turbulent blood flow be described and what is this due to?

A

Blood does not flow linearly and smoothly
in adjacent layers (whirlpools, eddies,
vortices)
Due to changes in
velocity

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12
Q

Where is bolus flow found?

A

Capillaries

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13
Q

How would bolus blood flow be described?

A

RBCs have larger diameter than diameter
of capillaries – single file
Plasma columns are trapped between RBC
Uniform velocity
Little internal friction - very low resistance

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14
Q

What is the equation for blood flow?

A

Blood flow = Arterial blood pressure/Total peripheral resistance

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15
Q

What is pressure exerted by blood on vessels generated by?

A

Pressure exerted by blood on vessel walls
Ultimately generated by
left ventricular ejection

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16
Q

What happens to arterial pressure in systemic circulation?

A

Arterial pressure falls in systemic circulation
with distance from left ventricle
and effect of different blood vessels

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17
Q

What helps to propel blood into circulation during diastole?

A

Recoil of elastic fibers of the aorta and large arteries helps to propel the blood into the circulation during diastole

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18
Q

What happens during LV ejection in terms of arterial blood pressure?

A

60-80% of stroke volume is stored
in aorta and arteries as these
structures expand
Energy stored in stretched elastin

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19
Q

What happens during LV diastole to arterial blood pressure?

A

Energy is returned to the blood as the walls
of the aorta and arteries contract
This sustains diastolic blood pressure and
blood flow when heart is relaxed

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20
Q

What is pulse pressure?

A

Pulse pressure is what the finger senses, e.g., at the wrist (radial artery)

21
Q

What does pulse pressure tell us about?

A

Pulse Pressure tells you about STROKE VOLUME and Large ARTERY COMPLIANCE (stretchiness)

22
Q

What is the equation for pulse pressure?

A

Pulse pressure = stroke volume / compliance

23
Q

What does a weak pulse mean in relation to stroke volume?

A

Reduce stroke volume

24
Q

Why does compliance decrease in the elderly?

A

Increase in age – stiffer arteries (arteriosclerosis) - decreased compliance
Increased systolic blood pressure

25
Q

What would happen to an elderly patient, with decreased compliance, if they were to exercise?

A

Very large increase in systolic pressure
Increase in afterload
Heart functions poorly

26
Q

What is the equation for blood flow?

A

Blood flow(Cardiac output) = Arterial blood pressure / Total peripheral resistance

27
Q

What is the equation for arterial blood pressure?

A

Arterial Blood Pressure = CO x TPR

28
Q

What 2 things does total peripheral resistance control?

A

Blood Flow and Blood Pressure

29
Q

What happens if you have excessive drop in TPR (excessive vasodilation)?

A

Excessive dilation will reduce blood pressure upstream to an extent
that there will be insufficient pressure drive for blood flow
Poor blood flow to end organs, organ/tissue damage

30
Q

What happens if you have excessive increase in TPR (excessive vasoconstriction)?

A

Excessive constriction leads to increase in blood pressure upstream and a
reduction in blood flow downstream
End organ damage

31
Q

What does poiseuille’s law describe?

A

Poiseuille’s Law describes parameters that govern TPR

32
Q

What is blood flow proportional to in terms of radius?

A

Blood Flow is proportional to Blood vessel radius to the power of 4 (r4)
-If you increase radius, you increase blood flow

33
Q

What is blood flow proportional to in terms of visocisty?

A

Blood flow is proportional to 1 / viscosity
-If you increase viscosity, you decrease blood flow

34
Q

What is TPR controlled by?

A

-Radius^4
-Pressure difference across vessels – P1-P2
-Length L

35
Q

What is arteriole radius tightly controlled by?

A

Arteriole radius is tightly controlled by
sympathetic nerves

36
Q

What vessels have the largest pressure drop?

A

Arterioles have largest pressure drop of 40-50 mmHg amongst vessels

37
Q

What is viscosity?

A

Viscosity is a measure of internal friction
opposing the separation of the lamina

38
Q

What does blood viscosity depend on?

A
  • Haematocrit
  • Velocity of blood
39
Q

What clinical implications does high haematocrit have on viscosity?

A

e.g., Polycythaemia - Increased TPR and BP, Decreased BF

40
Q

What clinical implications does low haematocrit have on viscosity?

A

e.g., Anaemia - TPR and BP (with HR
due to baroreflex compensation)

41
Q

What clinical implications does velocity of blood have on viscosity?

A

Increased viscosity in slow venous flow
in immobile legs
Increased risk of DVT

42
Q

Where is 60% of blood volume at rest found in?

A

60% of blood volume at rest is in
systemic veins and venules

43
Q

What do veins and venules function as?

A

Functions as blood reservoir

44
Q

How are veins innervated?

A

Innervated by sympathetic nerves which cause venoconstriction

45
Q

What happens when there’s increased venoconstriction?

A

Contraction of vessels – Expels blood into central veins
– Increases venous return/CVP/end-diastolic volume
– Increases stroke volume (Starling’s law)

46
Q

What is the equation for benous return?

A

Venous return = Venous Pressure – Pressure right atrium / Venous resistance

47
Q

How does the thoracic pump assist with blood returning to the heart?

A

Inhalation - thoracic cavity expands leading to increase in abdominal pressure, forcing
blood upward towards heart, increase right ventricular SV
Blood flows faster with inhalation

48
Q

What is retrograde flow in veins prevented by?

A

Retrograde flow is prevented by venous valves

49
Q

What does the skeletal muscle pump reduce?

A

Reduce high local venous pressures when in the upright position
Reduces swelling of feet and ankles – lower venous pressures, lower capillary
pressure, less filtration

Life support (38 decks)

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