Incomplete cartilagenous rings are present upto_____

Answer

**Step-by-Step Solution:**

1. **Understanding the Structure of the Respiratory System**: The respiratory system consists of various structures including the trachea, bronchi, bronchioles, and alveoli. Each of these structures plays a role in the process of breathing and gas exchange.

2. **Identifying the Trachea**: The trachea is the main airway that connects the larynx to the bronchi. It is a tubular structure that has incomplete cartilaginous rings that help maintain its shape and prevent collapse.

3. **Tracing the Division of the Trachea**: The trachea divides into two primary bronchi at the level of the 5th thoracic vertebra (T5). These primary bronchi further divide into secondary and tertiary bronchi.

4. **Understanding Bronchi and Bronchioles**: After the tertiary bronchi, the airway continues to branch into smaller tubes called bronchioles. The bronchioles further divide into terminal bronchioles.

5. **Identifying the Presence of Cartilaginous Rings**: In the respiratory system, incomplete cartilaginous rings are present in the trachea and continue through the primary, secondary, and tertiary bronchi. However, these rings are only present up to the terminal bronchioles.

6. **Conclusion**: Beyond the terminal bronchioles, the airway structures do not contain cartilaginous rings. Therefore, the incomplete cartilaginous rings are present up to the terminal bronchioles.

**Final Answer**: Incomplete cartilaginous rings are present up to the terminal bronchioles.

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