Gas Transport Flashcards
what is the difference between inspired (tracheal) air and atmospheric air?
- when you breathe in, it becomes saturated with water vapor
- the water vapor pressure varies with temperature
how does vapor pressure change in the respiratory system?
- at normal body temp, vapor pressure = 47mmHg
- when you increase temperature, you increase the partial pressure of water and vice verse
how do the partial pressures of oxygen and nitrogen change with vapor pressure being added?
they decrease! now have to factor in an additional pressure
how does the air change in the alveoli?
- this is the site of gas exchange, so O2 is absorbed into the blood and CO2 is added to the alveolar air
- the uptake of CO2 in the alveoli is not a drastic amount but a lot of O2 is absorbed into the blood
what is Henry’s law of dissolved gases? what does it tell us?
- the amount of gas that dissolves in a given volume of liquid is directly proportional to the partial pressure of that gas
- when there is a gas-liquid interface, the gas will dissolve into the liquid
- if you increase the pressure, there will be more diffusion and increase the concentration of dissolved gas
- this can be used to determine the amount of oxygen transported in the plasma
what is the structure of hemoglobin? why is it important?
- has 4 chains, iron, heme – 4 oxygen binding sites on each molecule of Hb
- depending on how many binding sites are occupied by oxygen determines the amount of oxygen transported by the blood
when fully saturated with oxygen, how much oxygen binds to 1 gram of Hb?
1.34 mL of O2 is bound = maximum per gram
what is oxygen capacity?
- the maximal amount of oxygen that will combine with the Hb of that blood
- varies with the Hb concentration of the blood
- O2 only binds to Hb
- important for understanding anemias (low Hb = low O2)
what is normal oxygen capacity?
- the normal amount of oxygen in the blood based on normal Hb levels
normal Hb = 15 grams/dLof blood
normal O2 capacity = 20.1 mL O2/dL of blood
what is oxygen saturation? (SO2)
- the percentage of the oxygen capacity that is actually occupied by oxygen
(how much is bound out of how much is there) - arterial ≈ 100%
- venous ≈ 75%
what is Hb bound oxygen content?
the concentration of oxygen that is bound to hemoglobin out of the maximal amount that you can hold (how many of the binding sites are full with O2)
what is total oxygen content?
- the total amount of oxygen dissolved in the blood (unbound) + the total amount of oxygen bound to hemoglobin
- sample questions on 136-139
what is the oxygen-Hb dissociation curve and what does it tell us?
- a graph that shows the relationship between the pressure of oxygen in blood, hemoglobin saturation, and Hb-O2 content
- when there is a higher pressure of oxygen (more of it) and higher hemoglobin saturation, there is a higher Hb-O2 content
- must have enough hemoglobin and oxygen to induce maximal binding between the two
- sigmoid relationship that results from heme-heme interactions
what happens to total oxygen content when oxygen partial pressure changes?
- increase PO2 = increase blood oxygen content bound to Hb
- there is a small amount of dissolved (unbound) O2
why is the oxyhemoglobin dissociation curve important for understanding gas transport and exchange?
- it tells us the relationship and binding affinity of Hb to oxygen in different parts of the body
- in the tissues, there is a lower binding affinity for O2, which allows for gas exchange – as you change the pressure, there are bigger changes to the saturation
- in the lungs, the affinity is much higher and small changes to pressure don’t affect the amount of bound O2 as significantly
what is the physiologic significance of the S-shape of the oxyhemoglobin dissociation curve?
- basically the same thing as the last card but in Edinger’s terms
how does arterial oxygen and HbO2 content compare to that of venous?
what happens to the Hb-O2 binding when you change the pH?
if you increase the concentration of H+ = decrease saturation of Hb-O2 at higher O2 pressures and vice verse
– lower pH = shift right
– higher pH = shift left
what happens to the Hb-O2 binding when you change the temperature?
if you increase temperature = decrease saturation of Hb-O2 at higher O2 pressures and vice verse
– higher temp = shift right
– lower temp = shift left
what happens to the Hb-O2 binding when you change the pressure of CO2?
if you increase CO2 = decrease saturation of Hb-O2 at higher O2 pressures and vice verse
– higher CO2 = shift right
– lower CO2 = shift left
why does CO2, H+, and temperature concentration have this affect on Hb-O2 binding?
- because these are consequences of tissue metabolism
- when you increase metabolism, the are products made by it and need to be rid of or taken else where
- O2 needs to go the the tissues so all of this is exchanged
- so blood looses O2 and gains the metabolism byproducts
what is anemia and polycythemia?
anemia = less than normal Hb and less RBCs
polycythemia = more than normal Hb and RBCs
what is the effect of anemia and polycythemia on the Hb-O2 dissociation curve?
- anemia = less Hb but full saturation – results in lower maximum HbO2 content but still full saturation
- polycythemia = higher Hb at full saturation – so there is a higher Hb-O2 content
how does carbon monoxide affect Hb-O2 binding?
- CO has a MUCH higher binding affinity for Hb than O2 does
- so sensitive that if PCO2 = 0.5mmHg, CO will be bound to 50% of Hb
- causes a shift to the left of the Hb-CO2 curve because CO will consume the binding sites
why is CO2’s ability to bind to amino groups important?
- because CO2 has an affinity for binding with amino groups and Hb has amino groups
- it is favored for CO2 to interact more with Hb because of the presence of amino groups
how is CO2 transported in the blood?
- bicarbonate!!! = the most important transporter of CO2
- to make bicarbonate, H2O + CO2 have to make carbonic acid – to do so is slow so you need carbonic anhydrase to speed it up
- carbonic acid isn’t very favorable for transport like bicarbonate, so there is small amounts of carbonic acid in blood and most is converted to bicarbonate
how does CO2 get transported?
- it is formed in the tissue as a byproduct of metabolism
- diffuses from tissue into the plasma and dissolved CO2 forms carbamino, carbonic acid, or bicarbonate
- also can go from plasma to RBCs and dissolved CO2 forms carbaminos, carbonic acid, or bicarbonate
- formation of bicarbonate is favored when there are lots of hydrogen ions that are buffered by Hb
- the RBCs forms so much bicarbonate that the bicarbonate can move from the RBCs into the plasma
- Cl ions also move into RBCs to maintain neutral charge
- water moves into RBCs to maintain an osmotic equilibrium thus cells swell
what is the total carbon dioxide content and in what forms is it found in the body?
- can be upwards of 50mL/dL
- mostly found in plasma bicarbonate
- can also be found as dissolved CO2, carbamino, red cell bicarbonate
how does oxygen and carbon dioxide compare?
