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MED 101- PHYSICS I > 17. PHYSICS OF THE CIRCULATION SYSTEM (PART 2) > Flashcards

17. PHYSICS OF THE CIRCULATION SYSTEM (PART 2) Flashcards

1
Q
  1. What is Aortic Narrowing and Arterial Stenosis
    (Narrowing)?
A
  • they are the localised narrowing in the arterial lumen
  • they are a result of atherosclerosis

ATHEROSCLEROSIS = a condition that develops when a
sticky substance (plaque) builds up
inside your arteries

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2
Q
  1. What is Arterial Stenosis often related to?
A
  • it can be genetic
  • blood related
  • lifestyle related
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3
Q
  1. With early Atherosclerosis, what are the features that are specific to Aortic Stenosis?
A
  • mechanical injury
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4
Q
  1. With intermediate Atherosclerosis, what are the features that are specific to Aortic Stenosis?
A
  • prominent early mineralisation
  • nodule formation
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5
Q
  1. With Late Atherosclerosis, what are the features that are specific to Aortic Stenosis?
A
  • heavy calcification
  • leaflet stiffening
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6
Q
  1. With early Atherosclerosis, what are the features that are specific to both Aortic Stenosis and Athero-Sclerosis?
A
  • endothelial injury
  • low shear stress
  • inflammation
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7
Q
  1. With intermediate Atherosclerosis, what are the features that are specific to both Aortic Stenosis and Athero-Sclerosis?
A
  • degradation of the extracellular matrix
  • lipid deposition
  • inflammation
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8
Q
  1. With late Atherosclerosis, what are the features that are specific to both Aortic Stenosis and Athero-Sclerosis?
A
  • calcification
  • fibrosis
  • inflammation
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9
Q
  1. With early Atherosclerosis, what are the features that are specific to Athero-Sclerosis?
A
  • fatty streak
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10
Q
  1. With intermediate Atherosclerosis, what are the features that are specific to Athero-Sclerosis?
A
  • foam cells
  • smooth muscle cells
  • proliferation
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11
Q
  1. With late Atherosclerosis, what are the features that are specific to Athero-Sclerosis?
A
  • plaque raptures
  • thrombus
  • FATAL
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12
Q
  1. Which ratio is Stenosis quantified by?
A
  • As / Ao
  • this is called the Area Ratio
  • it is expressed as a % of area occlusion
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13
Q
  1. How is the relation between the pressure drop across the stenosis (▵P) and the flow of blood (Q) mathematically expressed?
A

STENOTIC RESISTANCE INCREASES WITH FLOW

STENOSIS:
- caused additional quadratic pressure loses

THIS IS ON TOP OF THE ALREADY EXISTING:
- linear and proportional pressure loses

BOTH THE FLOW AND THE AREA APPEAR AS:
- quadratic terms
- this is an important aspect of the
hemodynamics of a narrowing

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14
Q
  1. What does the highlighted term represent?
A
  • this represents the viscous losses
  • these happen during Stenosis
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15
Q
  1. What does the highlighted term represent?
A
  • this represents the losses due to Turbulence

NB: Kt is an empirical coefficient
: it is equal to 1.5

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16
Q
  1. What happens with Severe Stenosis?
A
  • the area occlusion % is higher than 85%
  • the turbulent loses dominate
  • it results in significant resistance to blood flow
  • this is potentially harmful
  • it prevents adequate blood supply to distal beds
17
Q
  1. When the stenosis length (l) is assumed to be extremely small, what can be said about the pressure drop?
A
  • the pressure drop is proportional to the flow rate squared
  • the pressure drop is inversely related to the square of the cross-sectional area
18
Q
  1. What can be said about the pressure drop in laminar flow?
A
  • the pressure drop is proportional to the flow rate
19
Q
  1. What is a 90% stenosis 5 times more severe than?
A
  • an 80% stenosis
  • this is in terms of the pressure drop for a similar flow
20
Q
  1. What causes the complaints from Ischemia to arise suddenly?

ISCHEMIA = a condition in which blood flow and oxygen
are restricted/reduced in a part of the body

A
  • the non linear effect that occurs when the narrowing
    becomes more severe
  • this is typically found in a stenosis of 60% to 70%
21
Q
  1. According to Bernoulli’s Equation, what can be said about pressure at high velocities?
A
  • the pressure is low
  • the pressure in the narrow section may decrease to lower values
22
Q
  1. What is the result of stenosis occurring in vessels with Compliant walls?
A
  • there is a decrease in transmural pressure
  • this leads to extra narrowing
  • this worsens the situation

TRANSMURAL = existing or occurring across the entire
wall of an organ or blood vessel

23
Q
  1. Read through Summary 1.
    Does everything make sense?
A
  • yes
24
Q
  1. Read through Summary 2.
    Does everything make sense?
A
  • yes
25
Q
  1. Read through Summary 3.
    Does everything make sense?
A
  • yes
26
Q
  1. Read through Summary 4.
    Does everything make sense?
A
  • yes
27
Q
  1. Read through Summary 5.
    Does everything make sense?
A
  • yes
28
Q
  1. Read through Summary 6.
    Does everything make sense?
A
  • yes
29
Q
  1. Read through Summary 7.
    Does everything make sense?
A
  • yes
30
Q
  1. Read through Summary 8.
    Does everything make sense?
A
  • yes

MED 101- PHYSICS I (28 decks)

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