Midterm 2 - Gas Exchange

Question 1

why do gases exert pressure on the container

Answer 1

gas molecules are constantly moving/colliding

Question 2

what is total pressure determined by

Answer 2

the total number of gas molecules per volume unit

Question 3

what is partial pressure of gases

Answer 3

in a mixture = total pressure x % of that gas

Question 4

what is partial pressure independent of

Answer 4

other gases present in the mixture

Question 5

what is the pressure of air (dry)

Answer 5

760 mm Hg

Question 6

is air in the lungs dry

Answer 6

no

Question 7

what happens to inspired air

Answer 7

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

Question 8

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

Answer 8

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

Question 9

what is the relative amount of dissolved gas at equilibrium

Answer 9

constant

Question 10

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

Answer 10

solubility and partial pressure of the gas

Question 11

what does the presence of water do to gas content

Answer 11

dilutes it

Question 12

at 37 C, what is the water vapour pressure

Answer 12

47 mm Hg

Question 13

what is the mechanism of gas exchange

Answer 13

passive movement - diffusion

Question 14

what is the passive movement of gas molecules

Answer 14

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

Question 15

what is the air velocity in alveoli

Answer 15

0

Question 16

why is the air velocity in alveoli 0

Answer 16

due to large cross sectional area

Question 17

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

Answer 17

diffusion

Question 18

what is constant in alveoli

Answer 18

atmospheric partial pressures

Question 19

what does the diffusion of gases depend on

Answer 19

alveolar and blood partial pressures

Question 20

what does partial pressure in alveoli depend on

Answer 20

ventilation (how much air replaced in alveoli)

Question 21

what does partial pressure in blood depend on

Answer 21

tissue consumption

Question 22

what has a significant impact on diffusion

Answer 22

at higher altitude, pO2 in atmosphere decreases

Question 23

what is pCO2 in atmosphere lower than

Answer 23

lower in both alveoli and blood

Question 24

do changes in atmospheric pressure impact CO2 diffusion dramatically

Answer 24

no, unless in enclosed space

Question 25

what does gas exchange work between

Answer 25

alveoli and blood capillary network

Question 26

where is the blood in the capillaries coming from

Answer 26

the right ventricles

Question 27

are all capillaries in the lung coming from right ventricle

Answer 27

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

Question 28

what is the pO2 of blood entering alveolar capillaries

Answer 28

low

Question 29

where does O2 diffuse

Answer 29

from alveoli to blood

Question 30

where is pO2 the same in blood and alveoli

Answer 30

at the end of capillary

Question 31

where is pCO2 higher

Answer 31

in blood entering capillary then diffuses out towards alveoli

Question 32

what are the main determinants of gas exchange

Answer 32

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

Question 33

what happens when surface area is increased

Answer 33

more exchange

Question 34

what can capillaries do during exercises to increase exchange

Answer 34

open

Question 35

what happens during deep inspiration during exercises

Answer 35

the distance between alveoli and capillary endothelium is reduced

Question 36

what does perfusion correspond to

Answer 36

blood entering the lung

Question 37

what has to happen for optimum gas exchange

Answer 37

need to match ventilation with the blood flow

Question 38

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

Answer 38

no

Question 39

what impact does gravity have on gas exchange in bipeds

Answer 39

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

Question 40

is gas exchange better for bipeds or quadrupeds

Answer 40

quadrupeds

Question 41

what is V/Q

Answer 41

term used for ventilation/perfusion

Question 42

what is V/Q in humans

Answer 42

0.8

Question 43

when does V/Q become more uniform

Answer 43

during exercise - more blood is pumped throughout lung

Question 44

what can cause V/Q inequality

Answer 44

certain diseases which can affect V or Q of certain alveoli

Question 45

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

Answer 45

hypoxic vasoconstriction

Question 46

what does hypoxic vasoconstriction do

Answer 46

closes poorly ventilated alveoli redirects blood towards well ventilated alveioli

Question 47

what initiates hypoxic vasoconstriction

Answer 47

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

Question 48

what can cause impaired pulmonary gas exchange

Answer 48

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

Question 49

what is the consequence of a thickened alveolar-capillary membrane

Answer 49

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

Question 50

what is the consequence of high altitude or low air pO2

Answer 50

decreases alveolar oxygen pressure, hence decrease driving pressure

Question 51

what is hypoventilation

Answer 51

inadequate ventilation of lung

Question 52

what is V/Q inequality

Answer 52

ventilated alveoli with no blood supply or vice versa

Question 53

what does gas exchange in tissues follow

Answer 53

same principle as in alveoli

Question 54

what is diffusion driven by in tissues

Answer 54

difference in partial pressure

Question 55

in tissues, what do cells consume/produce

Answer 55

consume O2 produce CO2

Question 56

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

Answer 56

O2

Question 57

where does diffusion of O2 occur in tissue

Answer 57

from blood to interstitial fluid to the cells

Question 58

where does the diffusion of CO2 occur in tissue

Answer 58

from the cell to the interstitial fluid to the blood