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Tracheobronchial Tree

The tracheobronchial tree comprises the distal portion of the lower respiratory tract.
Tracheobronchial Tree
The tracheobronchial tree comprises the distal portion of the lower respiratory tract.
Key structures:
Trachea:
  • Cartilaginous "trunk" of the tree.
  • Comprises 15 – 20 C-shaped cartilaginous rings, are stacked vertically and connected via anular rings.
  • Trachealis posterior forms posterior wall of trachea; moves to accommodate foods passing posteriorly through the esophagus.
Bronchi:
  • Primary bronchi enter the lungs.
  • Secondary bronchi serve lobes of lung ("lobar" bronchi).
  • Tertiary bronchi serve bronchopulmonary segments ("segmental" bronchi); 10 on the right, 8-10 on the left.
Bronchioles:
  • Numerous, and narrow as they branch.
  • Have more smooth muscles in their walls, but still have cartilage in their walls.
  • Terminal bronchiole is the final passageway of the conduction portion of the respiratory system.
Respiratory bronchioles:
  • Demarcate the respiratory portion of the respiratory tract.
  • Thin walls allow some gas exchange.
Alveolar ducts:
  • Arise from respiratory bronchioles.
Alveolar sacs:
  • Terminal ends of the alveolar ducts.
Alveoli:
  • Thin-walled out-pockets of the alveolar sacs.
  • Surrounded by pulmonary capillaries.
  • Facilitate gas exchange between the respiratory and cardiovascular systems.
Lungs:
  • Hundreds of millions of alveoli.
  • Left lung = superior and inferior lobes; heart nestles into medial left lobe.
  • Right lung = superior, middle, and inferior lobes.
Clinical Correlations: