American Academy of Professional Coders (AAPC) Practice Exam

What defines a flat bone's cross-section?

1. It is round

2. It is thick

3. It is flat

4. It is tubular

The correct answer is: It is flat

A flat bone is characterized by its thin, flattened shape, which is reflected in its cross-section. This design allows flat bones, such as the sternum, ribs, and cranial bones, to provide protection to underlying organs while also serving as areas for muscle attachment. The flat nature facilitates a broad surface area that can absorb impact and distribute force more evenly. In contrast, round shapes may indicate bones that are categorized differently, such as long or irregular bones. Similarly, a thick cross-section would imply robustness more akin to the structure of a long bone or a short bone, which are designed for strength and support rather than flatness. Tubular shapes are descriptive of long bones, like femurs or humeri, which have a medullary cavity to house bone marrow. Thus, the defining feature of a flat bone's cross-section is its flatness, providing both structural and functional advantages.