Gerald F. Abbott, MD

Melissa L. Rosado-de-Christenson, MD, FACR



  • Secondary pulmonary lobule (SPL)

Overview of Airways


  • Tapering tubular structures

  • Asymmetric dichotomous branching beyond carina

Functional Zones

  • Conductive: Gas conduction through airways

    • Trachea and bronchi

    • Membranous and terminal bronchioles

  • Transitional: Gas conduction and exchange

    • Respiratory bronchi

    • Alveolar ducts

  • Respiratory: Gas exchange between inspired air and blood

    • Oxygen delivery to alveoli and carbon dioxide delivery to atmosphere

    • Alveoli and alveolar sacs

Anatomy of Airways


  • Largest airway

  • Connects larynx to main bronchi

  • Supported by incomplete (C-shaped) cartilage rings

  • Membranous posterior wall


  • Connect trachea to bronchioles

  • Crescent-shaped discontinuous cartilage in walls


  • < 1 mm in diameter

  • Lack cartilage in walls

Terminal Bronchioles

  • Last conducting airways

Respiratory Bronchioles

  • Connect terminal bronchioles to alveolar ducts

  • Walls contain alveoli, i.e., partially alveolated

Alveolar Ducts

  • Connect respiratory bronchioles to proximal alveolar sacs and alveoli

  • Walls completely alveolated, i.e., formed by alveoli

Alveolar Sacs & Alveoli

  • Small cup-shaped structures

  • Outpouchings from respiratory bronchioles, alveolar ducts, and alveolar sacs

Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Airways
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