The partial pressure of oxygen in inspired air..
Refer to figure.
EXCHANGE OF GASES
Gas exchange takes place in the alveolis in the lungs and the capillaries that envelop them. Inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide, that was produced by cells as a waste product, moves from the blood in the capillaries to the air in the alveoli to be exhaled. Thus, exhaled air contains more CO2 than inspired air (which contains more O2).
This gas exchange is based on the law of diffusion. Diffusion is the spontaneous movement of gases, without the use of any energy or effort by the body, where the gases will move from the area of high pressure into the area of lower pressure. Thus, rate of diffusion is dependent on the partial pressure gradients of O2 (pO2) and CO2 (pCO2).
This gas exchange is based on the law of diffusion. Diffusion is the spontaneous movement of gases, without the use of any energy or effort by the body, where the gases will move from the area of high pressure into the area of lower pressure. Thus, rate of diffusion is dependent on the partial pressure gradients of O2 (pO2) and CO2 (pCO2).
- This is how it happens: the partial pressure of inhaled O2 in the alveoli is higher (around 100 mmHg) than the partial pressure of O2 in the return blood (which is approximately 40 mmHg). Consequently, O2 will diffuse from the alveoli into the blood. Likewise, the partial pressure of CO2 in the return blood is higher (about 46 mmHg) than the partial pressure of CO2 in the alveoli (which is approximately 40 mmHg. As a result, the carbon dioxide will diffuse from the blood to the alveoli (lungs).
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