The lungs, it's how they breathe air, just like humans.
In mammals and fish it is lungs
The primary organ of the respiratory system is the lung.
mammal-lungs. Reptile-lungs+gills. Bird-lungs. Spider-book lung. Cockroach-trachea. Aquatic Arthopod-gills
that they are a type off a sail OK
Multicellular animals normally have body organs, yes.