Question
| A. |
Epiphysis |
| B. |
Metaphysis |
| C. |
Diaphysis |
| D. |
Physis |
|
Correct Answer » B Explanation |
 |
A long bone is divided into epiphysis, metaphysis, diaphysis, and physis. Each region has distinct structural and functional roles. The question asks for the most metabolically active region, i.e., the area with highest blood flow, turnover, and cellular activity.
The metaphysis is the most metabolically active part of a long bone because:
- It has rich blood supply with slow-flowing sinusoidal vessels
- It is the site of active bone remodeling and growth
- High cellular activity makes it prone to hematogenous infections (osteomyelitis)
Thus, it is considered the most metabolically active region.
Explanation of Other Options:
A. Epiphysis
Contains articular cartilage and secondary ossification center but is less metabolically active than metaphysis.
C. Diaphysis
Primarily composed of cortical bone; relatively less metabolic activity.
D. Physis (growth plate)
Site of longitudinal growth, but metabolically less active compared to metaphysis in terms of vascularity and turnover.