Phys 3 Gas exchange Flashcards
What does the bronchiole diameter control?
What controls the airway resistance?
This happens by the smooth muscle in airway walls
Why do we want to change airway resistance?
Point of the lungs is to bring what together?
What is Alveolar ventilation?
Perfusion?
J
What is it?
how much gas is exchanged every minute is equal to asking what is J
under normal conditions what is J?
CO2 vs O2 gas exchange
are they coupled?
what factors in the J equation are dependent on the structure of the alveolus?
S.A.
correspods to what?
- Lots of alveoli (millions)
- If a single layer= 70 sq. meters
- Also depends on number of “open” pulmonary capillaries
- varies with demand
- at rest approx 70 mL of blood in pulmonary capillaries
- exercise= as much as 200 mL
Altering S.A.
what disease can cause this?
If S.A. increases then J increases
Distance
what distance?
what creates this distance?
whats avg?
Diffusion distance (thickness of alveolar barrier)
Altering distance
what can alter it?
what does this cause?
what can cause the alteration?
- As distance increases, J decreases
- Lung of a patient with INTERSTITIAL LUNG DISEASE
- deposition of collagen has increased the distance for diffusion
D
what is it?
what does it depend on?
D of CO2 vs O2
O2 is less soluble than CO2 in water
Describe how the resistance of the airways is controlled and the consequences of changes in airway resistance?
(P1-P2)
consider each gas seperately
For CO2 it would be
40-45= -5 mm Hg
PACO2= 40
PVCO2= 45
so it would go out of RBC to the alveolar space
How long does it take to reach equillibrium (O2)
Normal conditions?
blood stays in for .75 seconds
In exercise equillibrium (O2)
Diffusion capacity of the lung for oxygen?
DL02
How do we measure it?
DLCO2
surface tension is between what?
how to measure pressure of round sac?
if there are changes in LaPlaces law (such as radius)
what happens
A pressure gradient is formed. air will go down gradient making small alveoli smaller and big alveoli bigger this will cause a cascade of smaller alveoli draining air to the bigger alveoli.
What prevents alveoli from having different pressures?
surfactant decreases T in proportion to the radius
which reduces pressure in the small alveoli
Surfactant produced by?
composed of?
stored?
