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Physiology Exam III Material > Pulmonary Gas Exchange > Flashcards

Pulmonary Gas Exchange Flashcards

1
Q

Components of air and their relative concentrations

A

Atmospheric pressure:

  • 78.09% nitrogen
  • 20.95% O2
  • 0.93% Argon
  • 0.03% CO2
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2
Q

Components of air at alveoli saturated with 6.18% water vapor

A
  • 73.26% Nitrogen
  • 19.65% O2
  • 0.87% argon
  • 0.03% CO2
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3
Q

What are the three gas laws

A
  • Dalton’s law
  • Boyle’s law
  • Henry’s law
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4
Q

What is Dalton’s law

A

The total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressure of individual gases

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5
Q

What is Boyle’s Law

A

For a fixed amount of an ideal gas kept at a fixed temperature, P (pressure) and V (volume) are inversely proportional

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6
Q

What is Henry’s Law

A

At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid directly proportional to the partial pressure of that gas in equilibrium with that liquid

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7
Q

Ideal gas law

A

P= nRT/V

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8
Q

Pressure is directly proportional to the

A

concentration of the gas molecules

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9
Q

The rate of diffusion is directly proportional to

A

pressure caused by that gas alone

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10
Q

A gas dissolved in a fluid also exerts its own ______ against a cell membrane

A

partial pressure

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11
Q

What is the partial pressure of CO2 at alveolar membrane

A

0.21 mm Hg

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12
Q

What is the partial pressure of O2 at alveolar membrane

A

=760x0.197

= 150mmHg

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13
Q

The partial pressure of a gas in solution is determined not only by its concentration but also by the __________ of the gas. This is _____ law

A

Solubility coefficient, Henry’s

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14
Q

equation for Henry’s law

A

partial pressure= dissolved gas / solubility coefficient

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15
Q

What is the solubility of oxygen

A

0.024

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16
Q

What is the solubility of carbon dioxide

A

0.57

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17
Q

Because carbon dioxide is _____ soluble in water than oxygen, it will exert a partial pressure (for a given concentration) that is ____ than _____ that of oxygen

A

more, less, 1/20th

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18
Q

______ of water is the partial pressure exerted to escape from the liquid phase to the gas phase

A

Vapor pressure

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19
Q

What is the vapor pressure of water at normal body temperature (37 degrees C)

A

47mmHg

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20
Q

Vapor pressure of water depends on the _____ of water. and decreases with

A

Temperature, decreases with a decrease in temperature

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21
Q

What are the 5 factors that affect rate of gas diffusion in a fluid

A
  • Solubility of gas in the fluid
  • Cross-sectional area of the fluid
  • Distance through which the gas must diffuse
  • Molecular weight of gas
  • Temperature of fluid (remains reasonably constant)
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22
Q

What is the functional residual capacity of the lungs of the average man

A

2300mL

23
Q

only ____ mL of new air is brought into the alveoli with each normal inspiration, and this same amount of old alveolar air is expired. Therefore, the volume of alveolar air replaced by new atmospheric air with each breath is only ____ of the total (2300mL), so multiple breaths are required to exchange most of the alveolar air

A

350mL, 1/7th

24
Q

oxygen concentration in the alveoli, as well as its partial pressure, is controlled by

A
  • Rate of absorption of oxygen into the blood

- Rate of new oxygen entry into the lungs (alveolar ventilation)

25
Q

to quadruple oxygen consumption, alveolar ventilation must

A

also be quadrupled

26
Q

Why can alveolar ventilation not increase PO2 above 149n, Hg under normal conditions

A

Because this is the maximum PO2 in humidified air at sea level pressure (if the person breathes gases that contain partial pressures of O2 higher than 149mmHg the alveolar PO2 can approach these higher pressures at high rates of ventilation.

27
Q

At moderate exercise the alveolar ventilation must increase _____ to maintain the normal alveolar PO2 of ____

A

4x, 104mmHg

28
Q

Carbon dioxide concentration in the alveoli, as well as its partial pressure, is controlled by

A
  • Rate of carbon dioxide excretion
    • Alveolar PCO2 increase in direct proportion to rate of excretion
  • Alveolar ventilation
    • Alveolar PCO2 decreases in inverse proportion to alveolar ventilation
29
Q

As Alveolar ventilation increases PCO2

A

decreases

30
Q

As PCO2 excretion increases Alveolar PCO2

A

increases

31
Q

What is the respiratory membrane (pulmonary membrane)

A

all terminal portions of the lungs, not merely in the alveoli

32
Q

Layers of the respiratory membrane

A
  1. ) A layer of fluid containing surfactant that lines the alveolus and reduces the surface tension of the alveolar fluid
  2. ) The Alveolar epithelium, which is composed of thin epithelial cells
  3. ) An epithelial basement membrane
  4. ) A thin interstitial space between the alveolar epithelium and the capillary membrane
  5. ) A capillary basement membrane that in many places fuses with the alveolar epithelial basement membrane
  6. ) The capillary endothelial membrane
33
Q

Components of the Respiratory unit

A
  • Respiratory Bronchiole
  • Alveolar ducts
  • Atria
  • Alveoli
34
Q

What is the overall thickness of the respiratory membrane

A

as little as 0.2 micrometers and averages 0.6 micrometers

35
Q

what is the total surface area of the respiratory membrane of a healthy adult male

A

about 70 square meters

36
Q

Factors that determine how rapidly a gas will pass through the respiratory membrane

A
  • Membrane thickness
  • Membrane surface area
  • Diffusion coefficient of gas in the substance of the membrane
  • Partial pressure difference of gas between the two sides of the membrane
37
Q

any factor that increases membrane thickness (ex. Edema or fibrosis) to more than ____ or ____ normal can interfere with gas exchange

A

2x or 3x

38
Q

Ventilation-Perfusion ratio

A

Va/Q= alveolar ventilatio/blood flow

39
Q

What is normal ventilation-perfusion ratio

A

0.8

ventilation= 4L/min / (pulmonary blood flow=5L/min)

40
Q

Gas exchange is complete in _____ of capillary

A

initial third

41
Q

what is normal alveolar CO2

A

40

42
Q

What is normal alveolar O2

A

100

43
Q

VA/Q equals 0 when Va=____ but there is still perfusion

A

0

44
Q

what is the reason for Va/Q=0

A

-due to airway obstruction (i.e. mucus plug)

45
Q

What happens to blood gas when Va/Q=0

A

Blood gas composition remains unchanged. This means it is the same O2 and CO2 as it was when it entered the capillary as when it comes out

46
Q

When is Va/Q equal to infinity

A

when Q=0, thus meaning there is still no ventilation (no gas exchange)
- due to vascular obstruction ()i.e. Pulmonary embolism)

47
Q

What happens to alveolar gas composition when Va/Q is equal to infinity

A

Alveolar gas composition remains unchanged(stays same as atm levels) because there is no blood contact. This creates a physiologic shunt

48
Q

Normal Alveolar perfusion PO2= and PCO2=

A 
PO2= 104 mmHg
PCO2= 40 mmHg
49
Q

The greater the physiological shunt, the _____ the amount of blood that fails to be oxygenated

A

greater

50
Q

Explain the physiologic shunt

A

Whenever Va/Q is below normal a certain fraction of the venous blood passing through the pulmonary capillaries does not become oxygenated. Also some blood is also shunted through bronchial vessels rather than through alveolar capillaries

The greater the physiologic shunt, the greater the amount of blood that fails to be oxygenated

51
Q

Physiological dead space

A
  • Sum of wasted alveolar ventialation (this is caused form great ventilation and poor blood flow leading to more oxygen available than can be transported by blood) plus anatomic dead space
52
Q

What is PO2 and PCO2 when Va/Q=0

A

PO2=40

PCO2=45

53
Q

What is PO2 and PCO2 when Va/Q=infinity

A

PO2=149

PCO2= 0

Physiology Exam III Material (13 decks)

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