Physiology question, respiratory system

[kov82]

---

Members don't see this ad.

PO2 concentration of blood to the lungs is 40 and arterial blood leaving lungs is PO2=100,

PCO2 concentration of blood to the lungs is 46 and arterial blood leaving lungs is PCO2=40,

I understand why it drops for CO2, because you breadth it out, but why is there such a small range in change for CO2 but a large one for O2?

 

[UndergradGuy7]

PO2 concentration of blood to the lungs is 40 and arterial blood leaving lungs is PO2=100,

PCO2 concentration of blood to the lungs is 46 and arterial blood leaving lungs is PCO2=40,

I understand why it drops for CO2, because you breadth it out, but why is there such a small range in change for CO2 but a large one for O2?

You don't have to memorize numbers, just know that blood going to the lungs has high CO2 and low O2 compared to blood leaving the lungs.

Anyway to answer your question. The CO2 reacts with H2O to make H2CO3 which then goes to HCO3-. It is buffered. So it does not exist as CO2. The partial pressure of CO2 only takes into account dissolved CO2, not CO2 in other forms such as HCO3-.