1. Bone Tissue

3. Of all the different types of connective tissues found in the body, bone is the most rigid, and it comes in two tissue forms called spongy bone and compact bone . As can be seen from this picture, under normal magnification spongy bone looks porous, while compact bone looks solid. Spongy Bone Compact Bone

4. A microscopic look at both types of bone tissue reveals two very different looks Spongy or Cancellous Bone Compact or Cortical bone

5. Compact bone is constructed in complex, cylindrical units called Haversian or Osteonic systems which are arranged directly next to each other and are “cemented” together with additional matrix material. This is what gives compact bone its “solid” look.

6. A more technical description of compact bone tissue is collagenous fibers embedded in a solid ground substance of calcium and magnesium salts, which is mostly calcium phosphate or the mineral hydroxyapatite , arranged in concentric cylindrical layers, called lamellae , enclosing a central canal (osteonic or “ Haversian” canal ) with “spider shaped” bone cells ( osteocytes ) lying in small spaces ( lacunae ) between the layers.

8. Spongy bone is matrix arranged as trabeculae , meaning “little beam,” which are bone “spicules” (which means a small, needlelike structure) that look like columns or “struts” with spaces between them. This is what gives spongy bone its porous look.