Questions: Arrange the following structures in the order air passes through them during inhalation: (1) alveolar ducts (2) alveolus (3) respiratory bronchiole (4) terminal bronchiole 4,3,2,1 1,2,3,4 3,2,1,4 2,1,3,4 4,3,1,2 The most common cell making up the alveolar wall is the:

The answer to the first question is the last one: \(4, 3, 1, 2\).

Explanation:

• During inhalation, air passes through the respiratory structures in the following order:
  1. Terminal bronchiole (4): This is the last part of the non-respiratory conducting airway, which leads to the respiratory bronchioles.
  2. Respiratory bronchiole (3): These are the first structures of the respiratory zone where gas exchange begins.
  3. Alveolar ducts (1): These are passages that connect the respiratory bronchioles to the alveolar sacs.
  4. Alveolus (2): These are the tiny air sacs where the exchange of oxygen and carbon dioxide occurs.

For the second question: The most common cell making up the alveolar wall is the Type I alveolar cell (also known as Type I pneumocyte). These cells are thin and cover about 95% of the alveolar surface area, facilitating efficient gas exchange.