Of which walls do respiratory gases diffuse through?

Question

is it through the small arteries, small veins, arterioles, or capillaries?

Answer 1

Respiratory gases like O2 and CO2 diffuse through the capillaries of the alveoli. The alveolar wall thickness is about 0.2 microns, and the capillary wall thickness is about the same. Gases like CO2, N2 and NO2 diffuse faster and reach equilibrium faster than O2.

Answer 2

1