What is the inner lining of a long bone called?

• A. Periosteum
• B. Endosteum
• C. Epiphysis
• D. Medullary cavity

Answer: (B)

The inner lining of a long bone is the endosteum. This thin membrane drapes the inside surfaces, including the walls of the medullary cavity and the inner surfaces of the cortical bone and trabeculae. It houses osteogenic cells that can become osteoblasts or osteoclasts, playing a key role in bone growth, remodeling, and repair from the inside. By contrast, the outer covering is the periosteum, the epiphyses are the bone ends, and the medullary cavity is the hollow interior that contains bone marrow.