lecture 13 Flashcards
what are some factors regulating movement of gas across the respiratory surface?
area?
huge surface area helping gas exchange
thickness of tissue
abcde and 0..5
partial pressure differential across tissue?
partial pressure of oxygen in the alveoli is 100 mmhg, but we lose 40-50 of the pressure by the time it gets to the alveoli. This is because there is residual gas which will dilute the fresh air, not all of it comes out, so next inhaled air will be contimationed it gets to the partial pressure of carbon dioxide is around 46 mmhg
10 times bigger driving force for oxygen compared to co2
solubility and molecular weight?
why is the rate of gas uptake across the alveolar membrane in gas diffusion and blood perfusion limited?
under resting conditions a rbc spends 3/4 of a second running around the capillary of the alveoli. You dont want this to be so quick that it doesnt have time to offload co2 and pick up o2, so the blood flow and the dynamics of these two processes have to be matched
the only we can pick up more oxygen is to increase diffusion because we still have half a second in which oxygen can be taken, we can speed up the flow rate of the alveoli as well to increase uptake of oxygen
overall: oxygen is perfusion limited meaning that there is plenty of capacity to increase perfusion and pick up more oxygen
carbon monoxide?
carrying capacity of blood for oxygen?
haemoglobin molecule?
one h molecule will take up four oxygen molecules
why does Haemoglobins affinity for oxygen change?
environment is different between the tissue and the lungs
the tissues are generating lots of co2, which is highly diffusable in blood and iwll combine with water to form carbonic acid, that freely dissociates to form hydrogen ions and bicarbonate ions
anaemia
reduced hb, everything is depressed (me core)
oxygen dissociation curve?
partial pressure of oxygen in the alveoli is 100 and in the tissues is 40 dependent on the metabolic demand of that tissue. We can see that hte relationship of saturation is dependent on Po2 in a sigmoidal fashion.
lungs is around 100 and tissues is around 40 so its like veins and arteries hmmm
okay this slide actually kind of makes sense
oxygen dissociation curve?
draw it
oxygen gets pushed into plasma when u add 100% pure oxygen
oxygen concentration increases with P02
shifting the o2 dissociation curve?
we talked about hydrogen ions and theya re being produced at the tissues and they help unload oxygen from Hb
at the tissues ther eis likely to be a slightly higher temperature than there is in the lungs, so the lungs will be running slightly cooler because youre breathing colder air from the outside
hotter temperature reduces the affinity of oxygen by hb
overall: both high h+ ions generated from the increased co2 and the increased co2 and the temperature will reduce the affinity of hameoglobin for oxygen, therefore helping unloading
the other factor here is dpg, a product of aerobic metabolism, dpg is really important becauase it will bind to hb, there is more in the tissues, and it helps offload oxygen in the tissues
left line = lungs
right line = tissues
middle line = the mean oxygen dissociation curve
bohr shift?
