The shaft of a long bone is called the

• A. End of a long bone
• B. Thin outer layer
• C. Shaft of a long bone
• D. Medullary cavity

Answer: (C)

Understanding long bone anatomy: the shaft is the diaphysis. The diaphysis is the elongated central part of a long bone, usually composed mainly of compact bone and enclosing the medullary cavity, which contains bone marrow. The ends are the epiphyses, the outer covering is the periosteum, and the inner lining is the endosteum. The medullary cavity sits inside the shaft, not in the ends. So when a question asks for the term for the shaft, the description that labels it as the shaft of a long bone directly matches the region in question. In precise anatomy, the shaft’s proper name is the diaphysis, but referring to it as the shaft aligns with the intended concept and differentiates it from the end, the outer layer, or the cavity.