The tiny sacs insure that the maximum area of tissue can be in close contact with the blood vessels to facilitate gas transfer
They are called Alveoli, look that up on wikipedia, or in your textbook.
lungs
alveoli
alveoli
Alveoli
Alveoli
The tiny sacs are called alveoli and are basically the lungs.
These "tiny sacs" are called vacuoles, but there are many other vacuoles that contain things other than starch.
alveoli
air sacs
tiny little sacs in lungs