Bronchioles are small tubes that branch off of bronchi
and connect to the air sacs (alveoli) in the lungs
. The word is derived from the Greek word bronchos, which refers to the passageways to the lungs. Bronchiolitis is a condition in which the bronchioles become inflamed. It occurs most commonly due to viral infections.
Image Source: MedicineNet, Inc.
Text Reference: University of California Keck School of Medicine: "Bronchus/Bronchi/Bronchioles"