Which of the following is not a part of the axial skeleton?

Options

A. Sternum
B. Coxal bone
C. Coccyx
D. Atlas

Answer

To solve the question "Which of the following is not a part of the axial skeleton?" we will analyze the given options and determine which one does not belong to the axial skeleton.

### Step-by-Step Solution:

1. **Understand the Axial Skeleton**:
- The axial skeleton consists of the bones that form the long axis of the body. This includes the skull, vertebral column, ribs, and sternum. The total number of bones in the axial skeleton is 80.

2. **Identify the Options**:
- The options provided are:
- A) Sternum
- B) Coaxial bone
- C) Coccyx
- D) Atlas

3. **Analyze Each Option**:
- **A) Sternum**: The sternum is part of the axial skeleton. It is located in the chest and connects the ribs.
- **B) Coaxial bone**: The coaxial bone (more commonly known as the coxal bone) is part of the pelvic girdle, which is part of the appendicular skeleton. Therefore, this option is not part of the axial skeleton.
- **C) Coccyx**: The coccyx, or tailbone, is part of the vertebral column, thus it is part of the axial skeleton.
- **D) Atlas**: The atlas is the first cervical vertebra and is also part of the axial skeleton.

4. **Conclusion**:
- The only option that is not a part of the axial skeleton is **B) Coaxial bone**.

### Final Answer:
**B) Coaxial bone**

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