Respiratory System in Humans -
- Respiratory Portion:
- Respiratory bronchioles
- Alveolar ducts
- Alveolar sacs and alveoli
- Each bronchus undergoes repeated divisions to form the secondary and tertiary bronchi and bronchioles ending up in very thin terminal bronchioles.
- The tracheae, primary, secondary and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings.
- Each terminal bronchiole gives rise to a number of very thin, irregular-walled and vascularised bag-like structures called alveoli.
- The branching network of bronchi, bronchioles and alveoli comprise the lungs.
Gaseous exchange takes place in the alveoli. Hence the correct option is alveoli
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