Compact bone and spongy bone are the two types of osseous tissue or bone tissue that make up bones. Although there may be different shaped bones that have unique functions, they are mostly composed of an outer layer of compact bone and an inner layer of spongy bone. An exception to this organization is the vertebrae that protect the spinal chord. The differences between compact and spongy bone can be summarize based on a few simple characteristics:
|Compact Bone||Spongy Bone|
|Other name||Cortical Bone||Trebeculae Bone|
|Location||Outer bone||Inner bone|
Due to the strength of compact bone, its main functions is to support the entire body. Compact pact bone also stores calcium. This serves two purposes at the same time. While calcium is being stored in the bone it is also the principle molecule that hardens compact bone.
Due to the sponge-like or porous nature of spongy or cancellous bone, spongy bone has a greater surface area compared to compact bone. This allows bone marrow to develop in the region of spongy bone. The branching nature of spongy bone also makes it a prime target in diseases such as osteoporosis. Since it is not compact, decreases in calcium avilability to this tissue can weaken it and cause the overall bone to break more easily.