Gas exchange in the lungs

• Air passes into the lungs through a tube called the trachea
• The trachea contains rings of cartilage to prevent it from collapsing during inhalation
• The trachea splits into two smaller tubes called the bronchi with one passing to each lung
• Further into the lungs the bronchi subdivide into smaller tubes called bronchioles
• The bronchioles end in tiny air sacks called alveoli
• The lungs contain a huge number of alveoli, which are tiny air sacs.
• The alveoli are where gasses diffuse in and out of the blood stream
• The millions of alveoli means the lungs have a huge surface area
• The alveoli have very thin walls so the diffusion path Is very short
• The alveoli have a very good blood supply this insures the concentration graidient is as steep as possible
• By breathing we also increase the rate of diffusion breathing brings freash oxygen into the alvioli and takes away carbon dioxide making the concentration gradient high for these gasses