Question

multiple choice question
indicate pathway of airflow from the more proximal to the more distal air passageway.
o secondary bronchus → tertiary bronchus → terminal bronchiole → respiratory bronchiole
o primary bronchus → secondary bronchus → respiratory bronchiole → terminal bronchiole
o terminal bronchiole → tertiary bronchus → secondary bronchus → primary bronchus

Explanation:

The primary bronchus is the most proximal (closer to the origin, which is the trachea). It branches into secondary bronchi, then tertiary bronchi. The bronchi further branch into bronchioles. Terminal bronchioles are more distal than tertiary bronchi, and respiratory bronchioles are even more distal (as they are part of the respiratory zone where gas exchange starts to occur). The correct order should follow the branching pattern from larger (more proximal) to smaller (more distal) airways.

• For the option “primary bronchus → secondary bronchus → respiratory bronchiole → terminal bronchiole”, terminal bronchioles are more proximal than respiratory bronchioles (terminal bronchioles are part of the conducting zone, and respiratory bronchioles are part of the respiratory zone which is more distal), so this order is wrong.
• For the option “terminal bronchiole → tertiary bronchus → secondary bronchus → primary bronchus”, it is in the reverse order (from distal to proximal instead of proximal to distal).
• The option “secondary bronchus → tertiary bronchus → terminal bronchiole → respiratory bronchiole” follows the correct proximal - to - distal order as per the branching pattern of the bronchial tree.

Answer:

secondary bronchus → tertiary bronchus → terminal bronchiole → respiratory bronchiole