It pumps blood into the veins of the animal
the air sac itself.
birds have air sac that work as bellow that ensure the unidirectional flow of air
The biological term for an air sac is alveolus. The plural is alveoli.
An alveolus is a single air-sac, and alveoli are multiple air-sacs.
It is easy for air to pass across the wall of an air sac because the wall is thin.
Alveoli is an air passage
A air sac
Air sac
Air sac
There is no specific name for this physiological feature of the kakapo. It is simply called an inflatable thoracic air sac.
there are millions of air sacs in your lungs
It's an Air Sac.