Which bone layer is known as cancellous or spongy bone?

• A. Periosteum
• B. Compact bone
• C. Cancellous bone
• D. Bone Marrow

Answer: (C)

In bone anatomy, there are two main dense tissue types: compact bone and cancellous bone. The layer known as cancellous or spongy bone is the porous, lattice-like interior found mainly at the ends of long bones and inside others. It’s made up of a network of trabeculae with spaces that often contain bone marrow. This structure keeps the bone light yet strong and provides a large surface area for metabolic processes like hematopoiesis. The outer dense shell is compact bone, the covering membrane is the periosteum, and bone marrow resides in the cavities but is not a separate bone layer.