Alveolar exchange Flashcards
(28 cards)
What is the partial pressure of atmospheric O2?
160 mm hg
What percentage of atmospheric air is oxygen?
21%
What state does gas diffuse into at the alveoli?
a liquid
What is added to the normal composition of air as it is brought into the lungs?
water
What is the composition of air in the lungs by percentages?
14% oxygen
75% Nitrogen
5% CO2
6% water
What 5 things affect the rate of diffusion of a gas?
- solubility of the gas in a liquid
- surface area of the barrier across which diffusion occurs
- distance of diffusion (membrane thickness)
- molecular weight of the gas
- Temperature
Why is aqueous diffusion the limiting factor?
respiratory gases are highly soluble in lipids (cells and tissue)
What are the partial pressures of O2 across the alveolar membranee on inspiration?
inside the alveoli: O2 is 104mm hg
outside the alveoli: O2 is 40 mm hg
What are the partial pressures of CO2 across the alveolar membrane on inspiration?
Inside the membrane: CO2 is 40 mm hg
Outside the membrane: CO2 is 46 mm hg
Can distance of diffusion be pathologically increased?
Yes
What is the functional residual capacity?
The amount of air that remains in the lungs after normal expiration.
What volume of air remains in the lungs after expiration?
2300 mL
How much air is being exchanged with each breath?
350 mL
What is the function of the functional residual capacity?
It acts as a buffer that prevents sudden changes in alveolar gas mix. This keeps blood gas levels relatively constant.
What is the partial pressure of O2 in the blood after it leaves the lungs and mixes with the shunted blood?
95 mm hg
What is the partial pressure of oxygen of individual cells in the periphery?
23 mm hg
Is oxygen more soluble as free O2 or when bound to Hb?
When bound to Hb
How many oxygen atoms do you get for each binding site on Hb?
2 atoms because it is elemental oxygen.
What does cooperative binding mean?
As each oxygen is bound, the affinity for the next one gets higher.
What is the most effective way to increase oxygen delivery to tissues?
Increase the concentration of Hb rather than partial pressure of O2.
How many subunits are on one Hb? How many Hb are on one RBC?
4, many
If cooperative binding keeps the O2 on a Hb very tightly, how do they dissociate?
When there is a low partial pressure of O2 in periphery, the opposite of cooperative binding occurs where with each O2 that dissociates, the easier it is for the next to dissociate.
What is the utilization coefficient? What is this number at rest and at exercise?
the percentage of blood that gives up its O2. At rest, it is 25% and during exercise it is 85%
Why is the disassociation curve of O2 sigmoidal?
The steep part of the curve represents cooperative binding, but as you aadd more you end up with diminishing returns, which is why it levels off at the top.
