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RESPIRATORY SYSTEM (GAS TRANSPORT IN THE BLOOD (Oxygen repels the plasma…
RESPIRATORY SYSTEM
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GAS EXCHANGE
In order for gases to move either across the membranes of the lungs and also across the membranes of the cells, we have to look at gas pressures for the individual gases. At sea level, the atmospheric pressure is 760 mmHg. Only some of this is due to oxygen. Air is made up of a combination of gases so the pressure is made up off all the parts; oxygen, carbon dioxide, nitrogen. This means that they each exert a partial pressure in the mixture. The symbols for these are as follows: PO2= partial pressure of oxygen; PCO2 = partial pressure of carbon dioxide. To see how this works, you already learned that oxygen is 21% in atmospheric air. The partial pressure of oxygen would be 0.21 X 760 mmHg = PO2 159.6.
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PULMONARY VENTILATION
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The change in pressure and volume links to a law called Boyle's Law. This law states that in a contained vessel as volume increases, pressure will decrease. And the reverse is also true so that as volume decreases, pressure increases. Of course this has to come with an equation: P1V1 = P2V2. Our thorax is a contained vessel in which we fill and empty our lungs this way.
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PULMONARY CAPACITY
VC = IRV + TV + ERV
Inspiratory Reserve Volume (IRV) - this is the maximum amount of air that one can inhale above the tidal volume
Tidal Volume (TV) - this is the normal amount of air one breathes at rest which is usually about 500mL
Expiratory Reserve Volume (ERV) - this is the maximum amount of air that one can exhale above the tidal volume
Residual Volume - this is the amount of air that remains in our lungs after the most forceful exhalation so our lungs don't collapse
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