What is the main shaft of a long bone called?

• A. Diaphysis
• B. Epiphysis
• C. Articulate Cartilage
• D. Periosteum

Answer: (A)

The main shaft of a long bone is known as the diaphysis. This central part is typically cylindrical in shape and composed primarily of compact bone, which provides strength and rigidity. The diaphysis serves several important functions; it houses the medullary cavity, which contains bone marrow, a crucial element for blood cell production. Additionally, it is instrumental in supporting weight and facilitating the bone's ability to withstand stresses during movement.

In contrast, the epiphysis refers to the end parts of the long bone, which are often involved in joint articulation, while the articulate cartilage covers the surfaces of the epiphysis to reduce friction and absorb shock at the joints. The periosteum is a dense layer of vascular connective tissue that envelops the outer surface of bones, playing a key role in bone growth and repair, but it is not the main shaft. Understanding these distinctions is essential in the study of skeletal anatomy and function in relation to athletic training.