The number of bicephalic ribs in human are:

Options

A. Seven pairs
B. Twelve pairs
C. Two pair
D. Three pairs

Answer

To determine the number of bicephalic ribs in humans, we need to understand the structure and classification of ribs.

### Step-by-Step Solution:

1. **Definition of Bicephalic Ribs**:
- Bicephalic ribs are those that have two articulation surfaces. This means they connect to two different structures: one end connects to the vertebral column (dorsal side) and the other end connects to the sternum (ventral side).

2. **Classification of Ribs**:
- Ribs are classified into three categories:
- **True Ribs**: These are the first seven pairs of ribs (1st to 7th) that directly articulate with the sternum. They are considered bicephalic because they have two articulation points.
- **False Ribs**: These are the next three pairs (8th, 9th, and 10th) that do not directly attach to the sternum but are connected to the 7th rib. They are not bicephalic.
- **Floating Ribs**: The last two pairs (11th and 12th) only articulate with the vertebral column and do not attach to the sternum at all. They also do not have two articulation points.

3. **Counting the Bicephalic Ribs**:
- Since only the true ribs (1st to 7th pairs) are bicephalic, we count these pairs:
- Total bicephalic ribs = 7 pairs (1st to 7th).

4. **Conclusion**:
- Therefore, the number of bicephalic ribs in humans is **7 pairs**.

### Final Answer:
The number of bicephalic ribs in humans is **7 pairs**.

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