1 – Alveolar saccules; 2 – Respiratory bronchiole (3-th order); 3 – Respiratory bronchiole (1-th order); 4 – Terminal bronchiole; 5 – Respiratory bronchiole (2-th order); 6 – Alveoli; 7 – Alveolar duct
1 – Alveolar saccules; 2 – Respiratory bronchiole (3-th order); 3 – Respiratory bronchiole (1-th order); 4 – Terminal bronchiole; 5 – Respiratory bronchiole (2-th order); 6 – Alveoli; 7 – Alveolar duct