The trachea, also known as the windpipe, is a part of the air passage that contains cartilaginous plates. These plates are C-shaped rings of cartilage that provide structural support to the trachea and help keep it open. The trachea is located in the upper part of the respiratory system, connecting the larynx (voice box) to the bronchi.

The bronchi are the two main branches that extend from the trachea into the lungs. They further divide into smaller and narrower tubes called bronchioles. While the bronchioles do not contain cartilaginous plates, the proximal portion of the bronchi, which are the larger airways closer to the trachea, do have cartilage rings.

1) Trachea:
- The trachea is a flexible tube that is composed of smooth muscle, connective tissue, and cartilaginous rings.
- The cartilaginous rings provide structural support to the trachea and prevent it from collapsing during respiration.
- The cartilage rings are incomplete at the back, allowing the trachea to expand and accommodate the movement of the esophagus behind it.

2) Distal portion of bronchi:
- The bronchi are the two main branches that extend from the trachea into the lungs.
- As the bronchi branch out into smaller tubes called bronchioles, the cartilaginous support decreases.
- The distal portion of the bronchi, which refers to the smaller airways further away from the trachea, does not contain cartilaginous plates.

3) Proximal portion of bronchi:
- The proximal portion of the bronchi refers to the larger airways closer to the trachea.
- These airways contain cartilaginous plates, similar to the trachea, to provide structural support.
- The cartilaginous plates in the proximal portion of the bronchi help maintain the shape and patency of the airway.

4) Bronchioles:
- The bronchioles are the smallest airways in the respiratory system.
- They do not contain cartilaginous plates but are instead surrounded by smooth muscle.
- The smooth muscle in the bronchioles allows for constriction or dilation of the airways, regulating airflow to the alveoli in the lungs.

In summary, while the trachea and the proximal portion of the bronchi contain cartilaginous plates, the distal portion of the bronchi and the bronchioles do not. The cartilaginous plates provide structural support and help keep the airways open, ensuring efficient airflow during respiration.

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