Which type of bone includes the humerus?

• A. Long bones
• B. Short bones
• C. Irregular bones
• D. Flat bones

Answer: (A)

Classification by shape is what this item tests. A long bone is longer than it is wide and has a central shaft (the diaphysis) with expanded ends (the epiphyses) that form joints. This structure provides leverage for movement and can handle large loads along the limb. The humerus fits this category because it has a long shaft with proximal and distal ends and acts as a major lever for the upper arm. In contrast, short bones are roughly cube-shaped, like the carpals and tarsals, and provide stability with limited lever action. Irregular bones have complex shapes, such as the vertebrae, and flat bones are thin and curved, like ribs and many skull bones, offering broad surfaces for muscle attachment or protection.