What is the name for small tube leading to airsac?

The small tubes leading to air sacs are called parabronchi. They connect the primary bronchi to the air sacs, which are the structures where gas exchange takes place in the lungs. Parabronchi are lined with capillaries, which are tiny blood vessels that allow oxygen to pass from the air sacs into the bloodstream, and carbon dioxide to pass from the bloodstream into the air sacs.