The humerus is an example of which category of bone?

• A. Short bone
• B. Irregular bone
• C. Long bone
• D. Sesamoid bone

Answer: (C)

A long bone is longer than it is wide and has a shaft (diaphysis) with proximal and distal ends (epiphyses) that typically articulate with joints for movement. The humerus fits this pattern: it has a long, cylindrical shaft and distinct ends that form the shoulder and elbow joints, with the outer wall mainly compact bone and a central medullary cavity inside. This shape supports leverage and body movement, which is the hallmark of long bones.

Short bones, in contrast, are roughly cube-like and nearly as wide as they are long (think wrist and ankle bones). Irregular bones have complex shapes that don’t fit the other categories (like vertebrae). Sesamoid bones are small bones embedded within tendons, such as the patella, and they function to modify tendon mechanics.