What is the term for the main shaft of a long bone, which is hollow and covered by compact bone?

• A. Epiphysis
• B. Diaphysis
• C. Medullary cavity
• D. Articular cartilage

Answer: (B)

The main shaft of a long bone is known as the diaphysis. It is characterized by its hollow structure, which allows for a reduction in weight while still providing strength and rigidity necessary for support and movement. The diaphysis is primarily composed of compact bone, which contributes to its strength and the ability to bear weight. This solid external layer protects the inner medullary cavity, which contains bone marrow, an important site for the production of blood cells. Understanding this term is crucial for recognizing the fundamental anatomy of long bones and how they function in the skeletal system.

The other terms refer to different components of a long bone: the epiphysis is the end part of the bone next to the joint; the medullary cavity is the hollow center within the diaphysis that houses bone marrow; and articular cartilage covers the surfaces of the bones that form joints, providing cushioning and facilitating smooth movement.