Diseases that can affect these airways include: Your airways branch into tiny tubes (bronchioles) that end in clusters of air sacs called alveoli. These air sacs make up most of your lung tissue.

The bronchi branch out into smaller tubes called bronchioles. At the ends of the bronchioles are little air sacs called alveoli. At the end of the alveoli are capillaries, which are tiny blood ...

A narrowing of the smallest airways in the lung (bronchioles) causes wheezing. This narrowing results from swelling caused by a virus. The respiratory syncytial virus (RSV) causes most bronchiolitis.

A narrowing of the smallest airways in the lung (bronchioles) causes wheezing. This narrowing results from swelling caused by a virus. The respiratory syncytial virus (RSV) causes most bronchiolitis.