Lung structure

300 million alveoli, 1/3mm in diameter => 50-100 m2 surface area

Z0 - Trachea

Z1 - Bronchi

Z4 - Bronchioles

Z16 - Terminal bronchioles

Z17-19 - Respiratory bronchioles

Z20-22 - Alveolar ducts

Z23 - Alveolar sac

Z0 to Z16 - Conducting airway

• No gas exchange
• i.e. anatomical dead space
• About 150mLs

Z17 to Z23 - Transitional and respiratory zone

• About 2.5L to 3Ls

Alveolar are polyhedral, not spherical, and not all surface areas are available for gas exchnge.

=> Total surface area can only be estimated.