Which bone tissue lines the medullary cavity of long bones?

• A. Spongy bone
• B. Compact bone
• C. Periosteum
• D. Endosteum

Answer: (D)

Verified step by step guidance

1. Understand the anatomy of a long bone: Long bones consist of several layers, including the outer periosteum, compact bone, spongy bone, and the medullary cavity, which is the hollow space inside the bone.
2. Learn the function of the medullary cavity: The medullary cavity is where bone marrow is stored, and it is lined by a specialized tissue called the endosteum.
3. Define the endosteum: The endosteum is a thin layer of connective tissue that lines the inner surface of the medullary cavity. It contains osteoblasts and osteoclasts, which are involved in bone remodeling and repair.
4. Differentiate the endosteum from other bone tissues: Compact bone forms the dense outer layer of the bone, spongy bone is found at the ends of long bones and within the epiphyses, and the periosteum is the outermost layer covering the bone. None of these tissues line the medullary cavity.
5. Conclude that the correct answer is the endosteum, as it specifically lines the medullary cavity and plays a role in bone maintenance and marrow support.