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BMS 242 - CVS respiratory > Biophysics and tissue fluid > Flashcards

Biophysics and tissue fluid Flashcards

1
Q

What is blood flow equal to?

A

Change in pressure/ resistance

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2
Q

What is the ‘change in pressure’ of blood flow?

A

Difference between the pressure at one end of the vessel compared to the other (between left ventricle and right atrium)

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3
Q

How does the length of the tube impact on resistance?

Why?

A

The LONGER the tube, the HIGHER the resistance

Cohesive forces and adhesive forces - blood sticks to the vessel wall

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4
Q

What has the biggest impact on blood flow?

Why?

A

RADIUS

Resistance = 1/R^4
Flow = change in pressure/ resistance
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5
Q

What vessels have the highest resistance?

A

Small arteries and aterioles

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6
Q

What is a key place where blood pressure can be treated?

A

The arterioles - target the receptors

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7
Q

What happens if blood pressure decreases substantially?

What is this called?

A

Tissues around the vessels will COMPRESS the blood vessel and cause them to COLLAPSE

Extravascular compression

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8
Q

What would occur to flow when increase the pressure, if vessels were RIDGED?

A

Increase on a LINEAR scale

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9
Q

What actually happens to flow when increase pressure in the vessel?

Why?

A
  • At FIRST, nothing happens - pressure inside the blood vessel pushes against the extravascular compression
  • Until get to a CRITICAL OPENING PRESSURE: pressure inside the blood vessels exceeds the pressure exerted by the extracellular tissue
  • Forces the vessel open - blood flow through the tube

BECAUSE: vessels are elastic

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10
Q

What is the ‘law of laplace’?

What does it apply to?

A

Transmural pressure = Tension/radius

Applies to OPEN vessels

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11
Q

What is the transmural pressure?

A

Pressure ACROSS the blood vessel wall

from the INSIDE to the OUTSIDE

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12
Q

What happens to the Ptm when radius increase?

A

Ptm decrease and the SLOWER the blood flow

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13
Q

What happens to the Ptm when radius decrease?

A

Ptm increase and the FASTER the blood flow

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14
Q

How is tension calculated?

A

Tension = Pr/W

P = pressure 
r = internal radius 
W = wall width
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15
Q

How does the wall width impact tension in the blood vessel?

A

The smaller the wall width, the greater the tension

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16
Q

What is an anuerysm?

What causes this?

A

Ballooning of an artery where a segment of wall is weakened

Caused by the pressure of the inside of the vessel wall

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17
Q

What does the tension across an aneurysm depend upon?

How?

What happens when the aneurysm grows?

A

The RADIUS itself:

Smaller the aneurysm - The greater the pressure across the wall

When grows:

  • Pressure across the wall becomes less
  • Aneurysm more likely to burst
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18
Q

What is compliance a measure of?

A

How much ‘give’ - how much pressure within the blood vessel causes it to expand

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19
Q

How does compliance vary?

A

Varies between blood vessels

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20
Q

How is compliance calculated?

A

Change in volume / change in pressure

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21
Q

What are the capacitance vessels?

Why?

A

Veins

More COMPLIANT that arteries - stretch at lower pressures
- Can store more blood

22
Q

What would happen to blood flow if the vessels were ridgid?

A
  • Would eventually stop further away from the heart (pressure decrease)
  • Pulsatile, discontinuous flow
23
Q

What actually happens to blood flow far away from the heart?

Why?

A

Pulsatile CONTINUOUS flow

Due to ELASTIC RECOIL in the vessels - Windkessel effect (squeezes the blood to make it continue to flow)

24
Q

Describe the flow rate in the aorta

Why?

A

Gets VERY high
Decreases RAPIDLY

(Very elastic)

25
Q

Describe the flow rate in the pulmonary artery

Why?

A

More CONSTANT flow rate (not as high, doesn’t decrease rapidly)

Lower pressure system

26
Q

What happens to the structure of the arteries as go lower down in the system?

A
  • LESS elastic

- MORE muscular

27
Q

Describe the flow rate in the pulmonary veins

A

Peak is VERY low and broad

28
Q

Describe the flow rate in the renal artery

Why?

A

Peak even lower than the pulmonary veins

Very muscular

29
Q

What determines if laminar or turbulent flow occurs?

A

1) DIAMETER of the vessel

2) SPEED of flow

30
Q

What is laminar blood flow?

A

SLOW
SMOOTH
STRAIGHT

31
Q

What are the consequences of laminar blood flow?

A

1) Blood in the centre of flow stay away from vessel walls - lower the ability to pick up oxygen

2) Layer of blood constantly in contact with the vessel wall
- cause blood clots

32
Q

When does turbulent blood flow occur?

A

When the SPEED of flow increases:

  • Blood hits the vessel wall and becomes turbulent
33
Q

What are the ADVANTAGES of turbulent blood flow?

A

1) Cells in the CENTRE of flow come into contact with the vessel wall - pick up oxygen
2) No stasis of blood - prevent blood clots

34
Q

What are the DISADVANTAGES of turbulent blood flow?

How is this overcome?

A

DAMAGE to red blood cells

Overcome as RBC are constantly made

35
Q

Where does gas exchange occur?

A

In the capillaries

36
Q

What is the structure of capillaries?

A 
Thin wall (one cell thick)
Fenestrations (gaps between cells)
37
Q

What is the velocity in the capillaries?

A

Very low

38
Q

What are the 2 states of the capillary?

What does this depend upon?

A

1) Active
2) Inactive (collapsed)

Which state depends upon the state of the PRE-CAPILLARY SPHINCTERS

39
Q

What do the pre-capillary sphincters do?

A

CONTROL and DIRECT blood flow into or away from the capillary bed

40
Q

What happens when pre-capillary sphincters are closed?

A

Blood is directed to OTHER parts of the body

41
Q

What is the net fluid transfer from the capillaries to tissues a balance of?

What does the net fluid transfer form?

A

FILTRATION and ABSORPTION

Forms TISSUE FLUID (extracellular or interstitial)

42
Q

How is fluid filtered through cells?

A

1) TRANSCELLULAR (Aquaporins)

2) PARACELLULAR (BETWEEN cells)

43
Q

What 3 things does tissue fluid formation depend upon?

A

1) PRESSURE difference between the CAPILLARY and the INTERSTITIAL fluid
2) Difference in COLLOID OSMOTIC PRESSURE (COP)
3) CAPILLARY FILTRATION COEFFICIENT (CFC)

44
Q

How does the pressure difference between the capillary and interstitial fluid influence tissue fluid formation?

A
  • Higher the pressure
  • Higher HYDROSTATIC pressure
  • MORE fluid pushed out
45
Q

What is COP formed by?

How does it influence tissue fluid formation?

A

The PROTEINS in the fluid (eg. Albumin)

  • More proteins in the BLOOD - HIGHER the COP, LESS the fluid will leak out into the tissue
  • Less proteins in the blood - LOWER the COP, formation of the tissue fluid is HIGHER
46
Q

When are the proteins low in the blood?

A

When starving

47
Q

What is the CFC?

What does it depend upon?

A

The ease of flow across a vessel wall

Dependant upon the gaps between the cells of the capillary

48
Q

What determines how much tissue fluid is made?

A

Balance between the HP (hydrostatic pressure) and COP (colloid osmotic pressure)

49
Q

Where is tissue fluid drained?

A

Into the lymphatic system and then into the great veins of the neck

50
Q

When is tissue fluid formed?

A

High blood pressure:

  • HP high - pushes fluid out through fenestrations
  • COP is LOW
  • More tissue fluid is formed

BMS 242 - CVS respiratory (15 decks)

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