The floor of thoracic cavity is formed by `"_____________"`

Answer

**Step-by-Step Solution:**

1. **Understanding the Thoracic Cavity**: The thoracic cavity, also known as the chest cavity, is a significant hollow space in the body that houses vital organs such as the heart and lungs.

2. **Structure of the Thoracic Cavity**: The thoracic cavity is enclosed by several structures:
- Ribs: These form the lateral walls.
- Vertebral Column: This forms the posterior wall.
- Sternum: This forms the anterior wall.

3. **Separation from Abdominal Cavity**: The thoracic cavity is separated from the abdominal cavity by a specific structure.

4. **Identifying the Floor of the Thoracic Cavity**: The floor of the thoracic cavity is formed by a muscular and membranous partition.

5. **Naming the Structure**: This structure is known as the diaphragm. It is a thin skeletal muscle that plays a crucial role in the process of breathing.

6. **Function of the Diaphragm**:
- During inhalation, the diaphragm contracts and flattens, allowing the lungs to expand and fill with air.
- During exhalation, the diaphragm relaxes, which helps push air out of the lungs.

7. **Conclusion**: Therefore, the floor of the thoracic cavity is formed by the diaphragm.

**Final Answer**: The floor of the thoracic cavity is formed by **diaphragm**.

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