Question

Arrange the following in the order in which inhaled air passes:
(res.= respiratory, ter.= terminal)

• A. Alveolar sacs
• B. Ter. bronchioles
• C. Alveoli
• D. Alveolar ducts
• E. Res. bronchioles

Answer 1

The bronchi extend out to form the terminal bronchioles and then the respiratory bronchioles. These then terminate to form the pulmonary acini or alveolar sacs which are made of air sacs called alveoli. The alveoli are present at the end of alveolar ducts. The alveoli are made up of cells called pneumocytes.
The respiratory bronchioles, alveolar ducts and the alveolar sacs containing the alveoli together to form the respiratory zone.