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20 Cards in this Set
- Front
- Back
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what is the PO2 in the aorta vs. RA? PCO2?
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aorta: PO2- 100
PCO2- 40 RA: PO2- 40 PCO2- 46 |
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what is the sequence of airways? which are involved in gas exchange?
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trachea->bronchi->bronchioles->terminal bronchioles->respiratory bronchioles->alveolar ducts->alveolar sacs
gas excahnge occurs ONLY at the alveolar ducts and sacs |
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what composes an alveolar wall? what are some properties?
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planar aggregate of capillaries; each surrounded by alveolar space; allows large SA for gas exchange with short distance for diffusion
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what are alveolar type 2 cells?
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make surfactant
covered in microvilli protrude into alveolar space |
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partial pressue of O2, N2 in room
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PO2= 160mmHg (160 Torr)
PN2= 600mmHg b/c atmosphere in 21% O2 and 79% N2 |
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what happens to the partial pressure of O2 and N2 when air is breathed into the lungs?
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another species of gas is added: water vapor. this changes the PO2 and PN2 because their relative concentrations change
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what is the partial pressure of water vapor at body temp (ie. in the airways)? how does this change PO2, PN2?
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ALWAYS 47mmHg
in airways: PO2=150, PN2=563 |
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if we are at high altitude in a chamber of CO2 but remain at body temperature what happens to the vapor pressure of water?
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nothing. vapor pressure of water depends ONLY on temperature
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what determines the movement of gases into fluids?
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gases dissolve into fluids by moving down PARTIAL PRESSURE gradients
ie. you can have gases move up a concentration gradient, dep on solubility of the gas in the 2 compartments |
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what can be said of the PO2 in the alveolus and capillary when at equilibrium?
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the PO2 are the same (100mmHg)
# gas mol entering fluid=#gas mol leaving |
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how do you determine how good an exchanger is?
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perfect exchanger: PAO2=PaO2
(A=alveolar gas being exhaled; a=arterial blood leaving lung) difference between PAO2 and PaO2 is A-a difference the larger the difference, the poorer the exchange |
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what determines how much gas is exchanged? (5)
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1. SA
2. thickness of mbr 3. solubility of gas in mbr 4. partial pressure gradient 5. degree of matching |
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what is meant by degree of matching?
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degree of ventilation vs. perfusion
if the are equal, ideal exchanger (minimal A-a difference) |
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what is dead space?
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wasted ventilation
ventilation without perfusion (Po>Pi) |
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what happens when airways are occluded? what is an ex?
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COPD
perfusion without ventilation; R->L shunt because blood leaves without being oxygenated no gas exchange dangerous because wasting blood flow |
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what happens when one airways is obstructed?
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shunt
PAO2 normal PaO2 low A-a difference large |
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what happens with a pulmonay embolus?
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dead space
PAO2 higher than normal PaO2 normal |
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what is PAO2?
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PO2 of air coming out of mouth from alveolus
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what is PaO2?
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PO2 in blood leaving lungs
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how does cross sectional area and resistance explain the requirement for cartilage rings in the upper airways?
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large, upper airways: low cross-sectional area, high resistance, high velocity, low lateral wall pressure (Bernoulli), high rate of collapse
small, lower airways- large cross-sectional area, low resistance, low velocity, high lateral wall pressure, no need for cartilage because wont collapse |
