What are bronchial tubes?

The tubes that branch from the trachea into each lung and that further branch into finer tubes called bronchioles are called bronchi (singular: bronchus) or bronchial tubes .
The trachea or windpipe branches into two primary bronchi, one each leading into each lung. These further divide and subdivide into secondary and tertiary bronchi which then lead into bronchioles that end in the alveoli which are the ##O_2## and ##CO_2## exchange interface.