Respiratory system during exercise of differing intensities and during recovery

Question 1

Explain why more O2 is diffused into the blood in the alveoli capillaries during exercise.

Answer 1

-Blood returning from muscles has lower pO2 when
exercising than at rest
-This creates a steeper diffusion gradient
-(between the high pO2 in the air and the lower in the
capillary)
-Causing a greater amount of diffusion

Question 2

Explain how O2 is diffused into the blood at the alveoli (external respiration).

Answer 2

-Blood (in the capillary) returning from muscles has low pO2
-Air breathed into the alveoli has high pO2
-This causes a diffusion gradient
-Gases always move from high pressure to low
pressure
-And O2 diffuses from the air into the blood