The last two pairs of ribs forming the sides of the chest cavity are called ..................

Explanation

**Step-by-Step Solution:**

1. **Understanding Ribs**: The human ribcage consists of 12 pairs of ribs, totaling 24 ribs. These ribs protect vital organs such as the lungs and heart.

2. **Types of Ribs**: Ribs are categorized into three types:
- **True Ribs**: The first 7 pairs (ribs 1-7) are called true ribs because they attach directly to the sternum (breastbone).
- **False Ribs**: The next 5 pairs (ribs 8-12) are known as false ribs. They do not attach directly to the sternum but connect to the last true rib or are indirectly connected.
- **Floating Ribs**: The last two pairs of ribs (ribs 11 and 12) are referred to as floating ribs. They are called so because they do not attach to the sternum or to the other ribs, making them free-floating.
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