but because avian lungs have much greater tissue density, they occupy about one-half the volume 1. The air sac system is a vital part of the avian respiratory system. Air sacs are thin-walled ...

Lungs are spongy, filled with tiny air sacs which give them a spongy texture. And our lungs are really large in surface area.

Bronchiole Each bronchus splits again and again into thousands of smaller tubes called bronchioles which take the air deeper into the lungs. Alveoli At the ends of bronchioles are tiny air sacs ...