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35 Cards in this Set
- Front
- Back
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Where does gas exchange take place?
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alveoli because of large surface area
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What composes the alveolar wall?
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capillaries with air space on either side
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What is the diffusion distance in the alveoli?
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very short to allow for rapid and efficient gas exchange between alveoli and RBC
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What makes up the atmosphere?
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mixture of 79% N2 and 21% O2
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What is the pressure exerted by O2?
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760 X .21= 160mmHg (PO2)
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Pressure exerted by N2?
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760 X .79= 600mmHg (PN2)
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What is partial pressure?
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the product of the specific gases mole fraction in the mixture and the total pressure exerted by all the gases
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What is the partial pressure of water vapor?
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47mmHg
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What is PO2 in the airways? N2?
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.21 X 713= 150
.79 X 713= 563 |
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What is a function of temperature?
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vapor pressure of water
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How do gases move?
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down partial pressure gradients
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How do you determine how good an exchanger is?
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a perfect exchanger will have the PO2 equal in both expired gas and arterial blood
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What is A-a difference?
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difference between PO2 in alveolar gas vs. PO2 in arterial blood; bigger difference means poorer exchange
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How does area affect gas exchange?
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greater area= more gas exchange
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How does thickness affect gas exchange?
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thinner the membrane the more gas is exchanged
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How does solubility affect gas exchange?
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greater the solubility the better the gas exchange
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How does the concentration gradient affect gas exchange?
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directly proportional to the difference in partial pressure between the gas and blood compartment
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How does degree of matching affect gas exchange?
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Most important factor! ventilation and perfusion much match; this means low A-A difference
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What happens when ventilation and perfusion are perfectly mismatched?
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no gas exchange takes place even with ventilation and perfusion; huge A-a difference
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What is a shunt?
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area is perfused but no gas exchange; lowers the PO2 in mixed blood leaving the lungs
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What happens when there is an occuluded blood vessel?
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no gas exchange taking place...gases are pumped there but no blood flow. gases become part of dead space (wasted ventilation)
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Which is more dangerous? shunt or dead space
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shunt
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What is a relaxation pressure curve?
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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
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How is a chest wall curve different than a lung curve?
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since it is rigid the air can be sucked out and it will exert a negative relaxation pressure
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What provides the energy needed to pump gases in and out of the lungs?
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chest wall
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What are 2 ways to inflate lungs?
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1. blow them up like a balloon
2. putting them in a space with negative pressure i.e. thorax |
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What model keeps the lungs inflated?
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held inflated by transmural pressure when Pin > Ppleural
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What is functional residual capacity?
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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
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What are the two factors in lung elastic recoil forces?
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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 |
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What is the main contributor to lung recoil?
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surface tension
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What causes surface tension?
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cohesive forces
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Why is surface tension relevant in the lungs?
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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
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What is the role of surfactant?
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reduce surface tension
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How does surfactant reduce surface tension?
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goes inbetween water molecules on the surface (because it is hydrophobic) and lowers the cohesive forces between water molecules
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Describe the difference between surfactant concentrations on different sizes of alveloi
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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
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