Bronchioles are air passages inside the lungs that branch off like tree limbs from the bronchi—the two main air passages into which air flows from the trachea (windpipe) after being inhaled through the nose or mouth. The bronchioles deliver air to tiny sacs called alveoli where oxygen and carbon dioxide are exchanged.

Where can bronchioles be found?

In your lungs, the main airways (bronchi) branch off into smaller and smaller passageways — the smallest, called bronchioles, lead to tiny air sacs (alveoli).

What are bronchioles in the lungs?

Inside your lungs, tubes split again and again, like the branches of a tree. The smallest of those branches are called bronchioles, and they end in tiny air sacs called alveoli. The alveoli are where the oxygen is picked up by your blood.