respiratory tree (anatomy)

Last reviewed 01/2018

In this text, the respiratory tree is taken to mean the branching portion of the respiratory tract within the thoracic cavity:

  • trachea
  • main bronchi
  • lobar bronchi
  • segmental bronchi
  • lobular bronchi
  • conducting bronchioles
  • terminal bronchioles
  • respiratory bronchioles
  • alveolar ducts
  • alveolar sacs
  • alveoli

There may be up to 28 divisions of the bronchial tree beyond the tracheal bifurcation. The proximal divisions are involved with air conduction whereas the latter divisions are adapted to gaseous exchange.

The areas of the lung supplied by successive divisions of the bronchial tree have special terms e.g.:

  • lobe - area supplied by a lobar bronchus
  • bronchopulmonary segment - area supplied by a segmental bronchus
  • lobule - area supplied by a terminal bronchiole