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Development of the Respiratory System Quiz
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Which of the following structures is part of the conducting portion of the respiratory system?
- A Alveolar sacs You picked ✕
- B Alveoli You picked ✕
- C Alveolar ducts You picked ✕
- D Bronchi You picked ✓
- E Respiratory bronchioles You picked ✕
Correct!
Incorrect
The answer is D: Bronchi
Explanation
Why D is correct
See Anatomical Divisions. Option D is correct. The airways can be divided by what they do. The conducting portion is the set of tubes that carry air in and out, warm and moisten it, and clear dust and microbes; no gas exchange takes place in it. It includes the trachea (windpipe), the bronchi (the two main branches of the trachea and their subdivisions) and the bronchioles (small airways without cartilage) up to and including the terminal bronchioles. The respiratory portion begins at the respiratory bronchioles, which have alveoli opening from their walls, and continues through the alveolar ducts to the alveoli and alveolar sacs. These have very thin walls and sit next to the pulmonary capillaries (the small blood vessels around the air sacs), so oxygen and carbon dioxide can pass between air and blood. A simple way to remember the border is that the conducting tubes end where the first alveoli appear.
- Conducting portion: carries, warms and cleans air with no gas exchange, from the trachea to the terminal bronchioles.
- Bronchi: the branches of the trachea are conducting tubes with no alveoli in their walls.
- Respiratory portion: begins at the respiratory bronchioles, where alveoli first open from the walls.
Only the bronchi, with the trachea and the bronchioles as far as the terminal bronchioles, are purely conducting.
Why the other options are incorrect
- A. Alveolar sacs: Alveolar sacs are the clusters of alveoli at the end of the airways, where gas exchange takes place. They sit in the respiratory portion at the end of the airway tree. They are the destination of the conducting airways rather than part of them. Your answer
- B. Alveoli: Alveoli are the tiny air sacs where oxygen and carbon dioxide cross into and out of the blood, so they belong to the respiratory portion. They are not part of the passage that simply carries air. They would be the answer to a question about the site of gas exchange. Your answer
- C. Alveolar ducts: Alveolar ducts are short passages lined by alveoli, and they open into clusters of air sacs. Because gas exchange happens along them, they belong to the respiratory portion. The conducting portion has no alveoli in its walls. Your answer
- E. Respiratory bronchioles: Respiratory bronchioles are the smallest bronchioles and have alveoli opening from their walls, so some gas exchange happens there. This makes them the start of the respiratory portion. The conducting portion ends at the terminal bronchioles, just before them. Your answer
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More questions from this set. Start the quiz to answer them and see each explanation.
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1
Which structure is part of the respiratory portion of the airway?
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2
A preterm infant born in the late second trimester develops respiratory distress shortly after birth because the alveoli expand poorly. Which alveolar cell type is mainly responsible for producing the substance that reduces surface tension within the alveoli?
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