Why is the sternum known to be bicephalic?

Options

A. It is made up of two different bones.
B. It has two articulation surfaces on its ventral end.
C. It has two articulation surfaces on its dorsal end.
D. Both (a) and (b)

Answer

### Step-by-Step Solution:

1. **Understanding the Term "Bicephalic":**
- The term "bicephalic" literally means "having two heads" or "two ends." In anatomical terms, it refers to a structure that has two distinct articulating surfaces or ends.

2. **Identifying the Structure of the Sternum:**
- The sternum is a flat bone located in the center of the chest, forming part of the ribcage. It serves as a central point of attachment for the ribs.

3. **Articulation with Ribs:**
- The sternum has two ends where it articulates with the ribs. Each rib has an articulating surface that connects to the sternum. This connection occurs at the dorsal end of each rib.

4. **Flat and Thin Nature of Ribs:**
- Each rib is described as a flat and thin bone. This structure allows them to connect vertically to the sternum, facilitating the bicephalic nature of the sternum.

5. **Conclusion:**
- Therefore, the sternum is referred to as bicephalic because it has two articulating surfaces (one for each side of the ribcage) that connect with the ribs, confirming its dual-ended structure.