How is the lung adapted for gas exchange?

Large surface area: Branches off, starting with bronchioles until microscopic in size with air filled sacs called alveoli. The alveoli also have massive capiliary networks surrounding them so there is a big surface area for the exchange of gases.

Small diffusion distance: The microscopic alveoli means tha gases only have to difuse through the epithelial cells of the alveoli and capilary before getting to the blood supply

Maintains concentration gradients: Air is constantly breathed in and out giving enough time for gas exchange and then swifty taking products away and replacing with fresh air. The blood networks surrounding alveoli also move oxygen away to maintain the gradient for oxygen to move in.

All of these follow the physical law, ficks law, which states that difusion is directly proportional to concentration gradient and surface area but indirectly proportional to diffusion distance.