The Alveoli has many features including-

• Good blood supply for maximum oxygen to enter the body
• Moist Lining for dissolving gases
• Very thin walls-it allows gasses to pass through
• Large surface area-the size of a tennis court

The nose and mouth produces;

Mucus-which traps dust particles and microbes.

To prevent the muscus blocking the lungs the trachea contains;

Cillia-ting, hair-like structures which move the muscus to the back of the throat where it can be swallowed.

The lungs are the main part of the human breathing system. They are adapted for gas exchanges. The  trachea is a tube bringing air from the nose and mouth to the lungs. It splits into two bronchi which branch further, ending in the alveoli which are tiny air sacs.

Did you know? : Inhaled air contains 21% oxygen and 0.04 carbon dioxide whereas exhaled air contains 17% oxygen and 4% carbon dioxide.