Gas Exchange And O2 CO2 Transport Flashcards
Random motion of molecules in all directions through the respiratory membrane and adjacent fluids
Diffusion
Caused by multiple impacts of moving molecules against a surface
Pressure
True or False
Pressure is directly proportional to the concentration of gas molecules
True
In respiratory physiology, one deals with mixture of gases:
Oxygen
Nitrogen
Carbon dioxide
Rate of diffusion of each of these gases directly proportional to the pressure cause by that gas alone
Partial pressure
Gases dissoleved in water or in body of tissues also exert pressure because
The dissolved gas molecule are moving randomly and have kinetic energy
Factors that determine the partial pressure of a gas dissolved in a fluid
Concentration/
Solubility coefficient of the gas
=partial pessure
Solubility coefficient highest to lowest
CO2>oxygen>CO>N>He
Which factor in the alveolar respiratory gas mixture tends to force molecules of that gas into solution in the blood of the alveolar capillaries
Partial prssure
In which direction will net diffusion of the gas occur?
In oxygen, more molecules will diffuse into the blood because PO2 is greater in the gas phase
In CO2, PCO2 is greater in the dissolved state so net diffusuon will occur toward the gas phase in the alveoli
Partial pressure that the water molecules exert to escape through the surface is called
Vapor pressure or PH2O
Vapor pressure normal value
47 mmHg
Factors that affect the rate of gas diffusion in the fluid (5)
Solubility of the gas on the fluid Cross sectional area of the fluid Distance through which the gas must diffuse Molecular weight of the gas Temperature of the fluid
(Soul Cross, Mold dis temp!)
The greater the solubility of the gas, the lesser the number of molecules available to diffuse
True or False
False. Lesser must be greater
These two factors determine the diffusion coefficient of the gas
Solubility and molecular weight
The relative rate at which different gases at the same partial pressure levels will diffuse
diffusion coefficient of the gas
Relative diffusion coefficients ranked:
CO2>O2>He>CO>N
The major limitation to the movt of gases in tissues
Rate at which the gases can diffuse through the tissue instead of the cell membranes
All are correct except:
A. Alveolar air is completely replaced with alveolar air with each breath
B. O2 is constantly absorbed into the pulmonary blood from the alveolar air
C. CO2 is constantly diffusing from the pulmonary blood into the alveoli
D. Dry atm air that enters the respi passages are being humidified even before it reaches the alveoli
A.Only partially
Composition of atm air except
N
O2
CO2
Water vapor
CO2 almost none
True or False
Total pressure in the alveoli can rise to more than the atm pressure (760mmHg at sea level) that this water vapor simply concentrates all the other gases in the humidification of the air
False. Cannot. Dilutes
Volume of alveolar air replaced by new atm air with each breath is only 1/6 of the total so multiple breaths are required to exchange most of the alveolar air.
T/F
1/7
Slow replacement if alveolar air is impt in
A. Preventing sudden changes in gas conc in the blood
B. Makes respo ctrl much more stable
C. Helps prevent excessive increases and decreases in tissue oxygenation, tissue CO2, and tissue pH when respiration is temp interrupted
D. AOTA
D.
O2 conc in the alveoli as well as its partial pressure is controlled by
Rate of absorption of O2 into the blood
Rate of entry of new O2 into the lungs by the ventilatory process
Normal value of alveolar PO2
104 mmHg
Max: 149mmHg
Normal operating rate for alveolar PCO2 at 4.2L/min
40mmHg
Alveolar PCO2 = rate of CO2 excretion/alveolar ventilation
True
Expired air is a combination of
Dead Space Air and Alveolar Air
Method for collecting alveolar air for study
Collecting a sample of the last portion of the expired air after forceful expiration has removed all the dead space air.
A respiratory unit is composed of
A. Respi lobule B. Respi bronchiole C. Alveolar ducts D. Atria E. Alveoli
Except A. That is the other name
Gas exhange between the alveolar air and the pulmonary blood occurs thru the membranes of only the terminal portions of the lungs.
T/F
false. In the alveoli also
Estimated total SA of the respi membranes is about
70 sq.m
Or 25x30ft. Floor
Average diameter of the pulm capillaries
5micrometers
Total qnty of blood in the capillaries at any given instant
60-140mm
Factors that affect the rate of gas diffusion through the respi membrane (4)
A. Thickness of the membrane
B. Surface area of the membrane
C. Diffusion coefficient of the gas in the substance of the membrane
D. Partial pressure difference of the gas between the two side of the membranes
In emphysema, many of the alveoli coalesce resulting to..
Which is true
A. Dissolution of many alveolar walls
B. SA is increased
A.
B should be decreased
Solubility sq.root of molecular weight
Diffusion coefficient
The difference between the two pressure in the alveoli and capillary is a measure of
The net tendency for the gas molecules to move through the membrane
Ability of the respi membrane to exchange a gas betw the alveoli and the pulm blood is expressed in qntive terms by the
Or
Volume of a gas that will diffuse thru the membrane each minute for a partial pressure difference of 1 mmHg
Respi membrane’s diffusing capacity
Ave. diffusing capacity for a young man
21 mL/min/mmHg
Mean O2 pressure difference across the respi membrane during normal quiet breathing
11mmHg
Under strenuous exercise, O2 diffusing capacity increases to
65 mL/min/mmHg
Diffusing capacity increase factors
Increased total surface area
Ventilation-perfusion ratio
CO2 assumed diffusing capacity
400-450 mL/min/mmHg
1200-1300mL/min/mmHg
20 times than that of O2
A certain fraction of the venous blood passing thru the pulm capilaries that does not become oxygenated
Shunted blood
Total qntive amount of shunted blood per minute
Physiological shunt
Greater the physiological shunt, the greater the amount of blood that fails to be oxygenated as it passes thru the lungs
True
Sum of the two types of wasted ventilation (alveolar and anatomical)
Physiological dead space
At the top of the lung, Va/Q is 2.5 times as great as the ideal value. This causes a moderate degree of
Physiologic dead space
In the bottom of the lung, there is slightly too little ventilation in relation to blood flow with Va/Q as low as 0.6x the ideal value. This represents
Physiological shunt
Most prevalent cause of pulmonary disability today
Emphysema for smokers
