In the alveoli
The gas occurs by simple diffusion through the cells.
Gas exchange does not occur in the respiratory tract, it occurs in the alveoli.
the alveolus
in the leave
gills
Gas exchanges occurs in the "alveoli".
gas exchange occurs between the thin walls of the alveoli and the thin walls of the capillaries
in their gills.
lungs
Gas exchange does not occur in the pleura. The pleura is a membrane that lines the outside of the lungs and inside of the chest cavity. Gas exchange, where oxygen is taken in and carbon dioxide is removed, happens in the alveoli of the lungs.
The gases are to dissolve and diffuse through.
Capillaries