Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physio > Gas Exchange And transport > Flashcards

Gas Exchange And transport Flashcards

1
Q

Percentages of different gases in air

A

. 78% Nitrogen
. 21% O2
. 1% argon
. Trace amounts CO2, H2O vapor, other gases, and pollutants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Dalton’s law

A 
. Partial pressure of a gas (x) in a gas mixture is the pressure that gas would exert if it occupied the total volume of the mixture in absence of the other components 
. Px = PB x Fx
. Px: partial pressure of gas x
. PB: total barometric dry gas pressure 
. Fx: fractional component of gas x
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

T/F total barometric pressure will change with altitude, but the percentage of each gas in the total air mixture will stay the same

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Henry’s law

A

. States that the concentration of a gas dissolved in a liquid (Cx) is equal to the partial pressure of that gas (Px) times its solubility in that liquid (alpha)
Cx = alpha x Px

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Partial pressure gradient

A

. Gas diffuses down its partial pressure gradient
. Normally, O2 diffuses from the alveoli and dissolves in pulmonary capillary blood until blood PO2 becomes equal to th partial pressure of O2 int he alveolar gas (PAO2)
. CO2 normally diffuses from pulmonary capillary blood and evolves as CO2 gas in the alveoli (PACO2) until alveolar PCO2 is equal to blood PCO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

composition of alveolar air

A

. Alveolar air has different composition than atmospheric air
. At body temp the partial pressure of H2O vapor is 47 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Effect of humidification of inspired air on partial pressure of gases

A

. It dilutes the partial pressure of the other inspired gases by 47 mmHg because the sum of all individual gas partial pressures must equal total barometric pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Alveolar gas equation

A

. PAO2 = PIO2 - (PACO2/RQ)
. PAO2: PO2 within alveoli
. PIO2: partial pressure of inspired O2
. PAO2 and PACO2 have an inverse linear relationship to one another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Partial pressure of O2 w/in alveoli throughout respiratory cycle

A

. Remains fairly constant
. O2 w/in alveoli continually moves down its partial pressure gradient into the blood
. New O2 arriving in the lungs w/ each breath replaces that which has already diffused into the pulmonary capillaries
. Pulmonary blood PO2 equilibrates w/ the alveolar PO2, the PO2 w/in the arterial blood also remains fairly constant at around 100 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Partial pressure of CO2 throughout respiratory cycle

A

. Body tissues continuously produce CO2
. CO2 added up in blood in the systemic capillary beds, and then is transported to the lungs
. When in lungs, CO2 diffuses down its partial pressure gradient, from the blood into the alveoli
. CO2 is removed from lungs during expiration
. Because CO2 arriving from the body tissues is constantly removed from the lungs, the PACO2 remains relatively constant throughout the cycle at 40 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Gas transfer w/in the pulmonary capillaries

A

. Blood entering pulmonary capillaries is systemic venous blood w/ a PO2 of 40 mmHg, and PCO2 of 46 mmHg
. Blood flows through pulmonary capillaries, is exposed to a PAO2 of 100 mmHg and PACO2 of 40 mmHg
. O2 flows down gradient from alveolar air into blood
. After O2 equilibration, blood leaving pulmonary capillaries has PO2 of 100 mmHg
. CO2 flows down gradient from blood into alveolar air
. After CO2 equilibration, blood leaving pulmonary capillaries has PCO2 of 40 mmHg
. Blood now higher in O2 and lower in CO2 is returned to heart and pumped to body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

PO2 w/in the systemic capillaries

A

. Arterial blood reaches systemic capillaries is same blood that left lungs w/ PO2 of 100 mmHg and PCO2 is 40 mmHg
. Each cell consumes O2 and produces CO2
. Cellular PO2 is 40 mmHg and PCO2 is 46 mmHg
. Values change based on cellular metabolism
. O2 moves by diffusion down gradient from systemic capillary blood (PO2 100 mmHg) into adjacent cells (PO2 40 mmHg) until equilibrium
. PO2 of blood that leaves systemic capillaries is equal to tissues PO2 (40 mmHg)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

PCO2 w/in systemic capillaries

A

. CO2 diffuses out of tissues (PCO2 46 mmHg) into capillary blood (PCO2 40 mmHg) down gradient until blood PCO2 equilibrates w/ the tissues PCO2
. PCO2 of the blood that leaves the systemic capillaries is equal to the tissue PCO2 ($^ mmHg)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Graham’s Law

A

. In the gas phase, the diffusion rate of molecules is inversely proportional to sq rt of molecular weights
. Diffusion rate = 1/ sq rt (MW)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Fick’s Law

A

. Volume of a gas that diffuses across a tissue sheet per unit time (Vgas)
. Vgas = A sol (P1-P2)/ d sq rt MW
. A: area of sheet
.d= thickness of the sheet
. D: diffusion constant (permeability coefficient of tissue for that gas)
(P1-P2): partial pressure gradient across membrane
. Sol: solubility
. MW: molecular weight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Blood flow in lungs during exercise

A

. During exercise when pulmonary blood pressure is raised as a result of inc. CO, many previously closed pulmonary capillaries are opened
. This inc. the SA available fo gas exchange

17
Q

Surface area of respiratory membrane in emphysema

A

. Many alveoli coalesce with dissolution of alveolar walls
. New alveoli are much larger than the original alveoli
. Total SA of respiratory membrane may dec. to 20% its original size

18
Q

Alveolar membrane thickness and affect on diffusion

A

. 0.5 um in thickness
. Rate of diffusion through the membrane is inversely proportional to thickness of the membrane
. Any factor that inc. the thickness can interfere w/ normal respiratory exchange of gases

19
Q

Pathological conditions that inc. thickness of respiratory membrane

A

. Pulmonary edema: excess accumulation of interstitial fluid btw alveoli and pulmonary capillaries
. Pulmonary fibrosis: involves replacement of delicate lung tissue w/ thick fibrous tissue in response to certain chronic irritants
. Pneumonia: characterized by inflammatory fluid accumulation w/in or around the alveoli

20
Q

Rate of gas transfer across the pulmonary membrane is proportional to ____

A

. Solubility of that gas
. Inversely proportional to its molecular weight
.

21
Q

CO2 and O2 solubility

A

. CO2 is more soluble in body tissues than is O2
. The rate of diffusion CO2 diffusion across respiratory membrane is 20 times more rapid than O2 for a given partial pressure gradient
. CO2 passes through alveolar membrane easier than O2

22
Q

Perfusion limited gas transfer

A

. Limit of time available for gas transfer
. N2O moves across respiratory membrane easily and dissolves in plasma
. N2O doesn’t combine w/ any substance in blood to its partial pressure in blood inc. rapidly
. Partial pressures on both sides of respiratory membrane equilibrate rapidly preventing further gas transfer
. Continued transfer of N2O can occur only if new blood is supplies to pulmonary capillary
. Amount of N2O taken up in blood depends on the rate of perfusion

23
Q

Diffusion limited gas transfer

A

. Gas tensions in the alveoli and the capillary blood fail to reach equilibrium during blood transit time through the capillary

24
Q

carbon monoxide gas transfer

A

. CO diffuses across respiratory membrane into the capillary blood down its partial pressure gradient
. Hb has high CO affinity so a large amount of CO is taken up by RBCs
. Partial pressure of CO in plasma remains low and CO gas continues to cross respiratory membrane down its partial pressure
. CO equilibrium btw alveoli and plasma is never achieved and the partial pressure gradient for CO will be high the entire time the blood spends in the pulmonary capillary
. CO limited only be diffusivity of alveolar membrane

25
Q

O2 uptake along pulmonary capillary

A

. Perfusion limited
. O2 diffuses across membrane and some O2 will bind to RBC but some stays dissolved in plasma
. Rise in PO2 in plasma will eventually cause equilibration

26
Q

Under resting conditions, the capillary PO2 is nearly the same as alveolar PO2 by the time ____

A

RBC is 1/3 along the way of the capillary

27
Q

O2 uptake along the pulmonary capillary during exercise

A

. CO inc. and the time th eRBC spends in capillary may be reduced
. PO2 of blood will equilibrate w/ alveolar PO2 before the blood completely passes though the capillary
. W/ disease, there may not be enough time for equilibration and PO2 will inc. More slowly in capillary blood showing diffusion impairment

28
Q

Diffusing capacity

A

. DL = Vgas/PAgas
. Vgas: amount of gas transferred
. PAgas: partial pressure of gas in alveoli

29
Q

How DLCO is measured

A

. Single breath of CO
. Single inspiration of dilute mixture is made and the rate fo disappearance of CO for alveolar gas calculated
. Done by measuring inspired and expired concentrations of CO w/ infrared analyzer
. Normal value 25 ml/min/mmHg
. Can inc. 2-3x during exercise

30
Q

Examples of conditions have thicken the barrier

A

. Interstitial/alveolar edema

. Interstitial/alveolar fibrosis

31
Q

Conditions that cause dec. surface area

A

. Emphysema
. Low CO
. Low pulmonary capillary blood volume

32
Q

Conditions that cause Dec. uptake by erythrocytes

A

. Anemia

. Low pulmonary capillary blood volume

Physio (62 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions