Which bone tissue is located just inside the layer of compact bone and contains many small spaces?

• A. Spongy bone
• B. Compact bone
• C. Endosteum
• D. Yellow marrow

Answer: (A)

Spongy bone, or cancellous bone, is the porous tissue found just inside the dense outer layer. Its lattice of trabeculae creates many small spaces, which house bone marrow and keep the bone strong yet light. This contrasts with the dense, solid compact bone that makes up the outer shell. The inner lining of bone is the endosteum, a membrane rather than a bone tissue with spaces, and yellow marrow is adipose tissue filling some of the cavity spaces rather than a bone tissue itself.