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35 Cards in this Set

  • Front
  • Back
Where does gas exchange take place?
alveoli because of large surface area
What composes the alveolar wall?
capillaries with air space on either side
What is the diffusion distance in the alveoli?
very short to allow for rapid and efficient gas exchange between alveoli and RBC
What makes up the atmosphere?
mixture of 79% N2 and 21% O2
What is the pressure exerted by O2?
760 X .21= 160mmHg (PO2)
Pressure exerted by N2?
760 X .79= 600mmHg (PN2)
What is partial pressure?
the product of the specific gases mole fraction in the mixture and the total pressure exerted by all the gases
What is the partial pressure of water vapor?
What is PO2 in the airways? N2?
.21 X 713= 150
.79 X 713= 563
What is a function of temperature?
vapor pressure of water
How do gases move?
down partial pressure gradients
How do you determine how good an exchanger is?
a perfect exchanger will have the PO2 equal in both expired gas and arterial blood
What is A-a difference?
difference between PO2 in alveolar gas vs. PO2 in arterial blood; bigger difference means poorer exchange
How does area affect gas exchange?
greater area= more gas exchange
How does thickness affect gas exchange?
thinner the membrane the more gas is exchanged
How does solubility affect gas exchange?
greater the solubility the better the gas exchange
How does the concentration gradient affect gas exchange?
directly proportional to the difference in partial pressure between the gas and blood compartment
How does degree of matching affect gas exchange?
Most important factor! ventilation and perfusion much match; this means low A-A difference
What happens when ventilation and perfusion are perfectly mismatched?
no gas exchange takes place even with ventilation and perfusion; huge A-a difference
What is a shunt?
area is perfused but no gas exchange; lowers the PO2 in mixed blood leaving the lungs
What happens when there is an occuluded blood vessel?
no gas exchange taking place...gases are pumped there but no blood flow. gases become part of dead space (wasted ventilation)
Which is more dangerous? shunt or dead space
What is a relaxation pressure curve?
measured by taking the structure of interest, blowing it up to some volume, plugging its orifice and then measuring how much pressure it exerts at its orifice
How is a chest wall curve different than a lung curve?
since it is rigid the air can be sucked out and it will exert a negative relaxation pressure
What provides the energy needed to pump gases in and out of the lungs?
chest wall
What are 2 ways to inflate lungs?
1. blow them up like a balloon
2. putting them in a space with negative pressure i.e. thorax
What model keeps the lungs inflated?
held inflated by transmural pressure when Pin > Ppleural
What is functional residual capacity?
where the elastic recoil forces of lung and chest wall are equal and opposite; amount of gas present in the lungs when mouth is open and respiratory muscles are all relaxed
What are the two factors in lung elastic recoil forces?
1. lung tissue elastic recoil- comes from the polymer molecules that make up the lung
2. surface tension forces- each alveolus is basically a water-lined compartment; the water exerts surface tension forces that act to reduce the size of the surface
What is the main contributor to lung recoil?
surface tension
What causes surface tension?
cohesive forces
Why is surface tension relevant in the lungs?
in the alveolus surface tensions tend to collapse it because there is a collective downward force when the water molecule sits on the surface; forces are not balanced
What is the role of surfactant?
reduce surface tension
How does surfactant reduce surface tension?
goes inbetween water molecules on the surface (because it is hydrophobic) and lowers the cohesive forces between water molecules
Describe the difference between surfactant concentrations on different sizes of alveloi
all have identical amounts but it is more concentrated in the smaller ones so the net surface tension is lower there allowing for the bigger one to have a higher pressure