Bronchioles

Bronchioles

Tertiary bronchi divided into terminal branchioles (very small branches).

Terminal branchioles divided into small branches called respiratory branchioles.

Respiratory branchioles ends in microscopic passage form alveoli ducts, alveoli sacs and alveoli. 

Tracheobronchial Tree

Trachea and two primary bronchi referred as bronchial tree. 

Trachea (conducting portion consist) "dead space" air is present in that area but no gas exchange occurring. Epithelium tissue help to remove debris from air.

 Bronchi, Primary bronchi

Secondary bronchi

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Tertiary bronchi

Bronchioles-Terminal bronchioles

Respiratory bronchioles (gas exchange happen) respiratory portion consist-

Alveolar duct

Alveolar sacs

Alveoli

Bronchi consists cartilage and mucus glands in their walls but bronchioles do not.

Bronchioles contains more smooth muscle tissue than bronchi.

Both bronchi and bronchioles are lined with ciliated columnar epithelium.

Respiratory bronchioles more deeply into lungs. Epithelial lining changes from simple cubodial to simple squamous in the alveolar duct and alveoli.