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ANSC 3080 > Midterm 2 - Gas Exchange > Flashcards

Midterm 2 - Gas Exchange Flashcards

1
Q

why do gases exert pressure on the container

A

gas molecules are constantly moving/colliding

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2
Q

what is total pressure determined by

A

the total number of gas molecules per volume unit

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3
Q

what is partial pressure of gases

A

in a mixture = total pressure x % of that gas

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4
Q

what is partial pressure independent of

A

other gases present in the mixture

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5
Q

what is the pressure of air (dry)

A

760 mm Hg

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6
Q

is air in the lungs dry

A

no

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7
Q

what happens to inspired air

A

it is 100% saturated with water when it reaches the respiratory zone

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8
Q

what happens to some of the gas molecules when colliding with water

A

they get dissolved in water which is slightly different than for dry air

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9
Q

what is the relative amount of dissolved gas at equilibrium

A

constant

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10
Q

what does the relative amount of dissolved gas at equilibrium depend on

A

solubility and partial pressure of the gas

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11
Q

what does the presence of water do to gas content

A

dilutes it

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12
Q

at 37 C, what is the water vapour pressure

A

47 mm Hg

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13
Q

what is the mechanism of gas exchange

A

passive movement - diffusion

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14
Q

what is the passive movement of gas molecules

A

from regions of high concentration (partial pressure) to regions of low concentration (partial pressure)

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15
Q

what is the air velocity in alveoli

A

0

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16
Q

why is the air velocity in alveoli 0

A

due to large cross sectional area

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17
Q

what is the only way there can be movement from alveoli to alveolar-capillary membrane

A

diffusion

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18
Q

what is constant in alveoli

A

atmospheric partial pressures

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19
Q

what does the diffusion of gases depend on

A

alveolar and blood partial pressures

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20
Q

what does partial pressure in alveoli depend on

A

ventilation (how much air replaced in alveoli)

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21
Q

what does partial pressure in blood depend on

A

tissue consumption

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22
Q

what has a significant impact on diffusion

A

at higher altitude, pO2 in atmosphere decreases

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23
Q

what is pCO2 in atmosphere lower than

A

lower in both alveoli and blood

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24
Q

do changes in atmospheric pressure impact CO2 diffusion dramatically

A

no, unless in enclosed space

25
Q

what does gas exchange work between

A

alveoli and blood capillary network

26
Q

where is the blood in the capillaries coming from

A

the right ventricles

27
Q

are all capillaries in the lung coming from right ventricle

A

no - some capillaries are from left to bring oxygen to lung tissue

28
Q

what is the pO2 of blood entering alveolar capillaries

A

low

29
Q

where does O2 diffuse

A

from alveoli to blood

30
Q

where is pO2 the same in blood and alveoli

A

at the end of capillary

31
Q

where is pCO2 higher

A

in blood entering capillary then diffuses out towards alveoli

32
Q

what are the main determinants of gas exchange

A

driving partial pressure gradient
surface area available for diffusion
thickness of the air-blood barrier
physical properties of gas

33
Q

what happens when surface area is increased

A

more exchange

34
Q

what can capillaries do during exercises to increase exchange

A

open

35
Q

what happens during deep inspiration during exercises

A

the distance between alveoli and capillary endothelium is reduced

36
Q

what does perfusion correspond to

A

blood entering the lung

37
Q

what has to happen for optimum gas exchange

A

need to match ventilation with the blood flow

38
Q

for bipeds (humans) at rest, is gas exchange optimum

A

no

39
Q

what impact does gravity have on gas exchange in bipeds

A

perfusion (blood flow) is lowest at the top of the lung (capillaries can collapse) - not so pronounced for ventilation

40
Q

is gas exchange better for bipeds or quadrupeds

A

quadrupeds

41
Q

what is V/Q

A

term used for ventilation/perfusion

42
Q

what is V/Q in humans

A

0.8

43
Q

when does V/Q become more uniform

A

during exercise - more blood is pumped throughout lung

44
Q

what can cause V/Q inequality

A

certain diseases which can affect V or Q of certain alveoli

45
Q

what is the natural mechanism that minimizes impact of V/Q inequality

A

hypoxic vasoconstriction

46
Q

what does hypoxic vasoconstriction do

A

closes poorly ventilated alveoli
redirects blood towards well ventilated alveioli

47
Q

what initiates hypoxic vasoconstriction

A

reduction of pO2 and/or increase in pCO2 in the interstitial fluid of affected areas

48
Q

what can cause impaired pulmonary gas exchange

A

thickening og alveolar-capillary membrane
high altitude or low air pO2
hypoventilation
ventilation-perfusion inequality

49
Q

what is the consequence of a thickened alveolar-capillary membrane

A

increases the time for diffusion across the membrane and decreases the rate of diffusion

50
Q

what is the consequence of high altitude or low air pO2

A

decreases alveolar oxygen pressure, hence decrease driving pressure

51
Q

what is hypoventilation

A

inadequate ventilation of lung

52
Q

what is V/Q inequality

A

ventilated alveoli with no blood supply or vice versa

53
Q

what does gas exchange in tissues follow

A

same principle as in alveoli

54
Q

what is diffusion driven by in tissues

A

difference in partial pressure

55
Q

in tissues, what do cells consume/produce

A

consume O2
produce CO2

56
Q

what is the blood from the left side of the heart loaded with

A

O2

57
Q

where does diffusion of O2 occur in tissue

A

from blood to interstitial fluid to the cells

58
Q

where does the diffusion of CO2 occur in tissue

A

from the cell to the interstitial fluid to the blood

ANSC 3080 (41 decks)

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