1. Tardigrade
  2. Question
  3. Biology
  4. Which statements about the human gas exchange system are correct? I. The absence of cartilage in small bronchioles allows them to expand. II. The walls of the alveoli are made of cuboidal epithelium. III. The recoil of the elastic fibres surrounding the alveoli helps to move air out during expiration. IV. The trachea and bronchi are supported by circles of cartilage.

Q. Which statements about the human gas exchange system are correct?
I. The absence of cartilage in small bronchioles allows them to expand.
II. The walls of the alveoli are made of cuboidal epithelium.
III. The recoil of the elastic fibres surrounding the alveoli helps to move air out during expiration.
IV. The trachea and bronchi are supported by circles of cartilage.

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Solution:

The tracheae, primary, secondary and tertiary bronchi 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 made of squamous epithelium. Alveolar walls contain elastic fibres which stretch during inspiration and recoil during expiration to help force out air. This elasticity allows alveoli to expand according to the volume of air breathed in.