Haversian System

Compact bone is very hard and dense. It consists of microscopic cylindrical structures oriented parallel to the long axis of a bone. The cylindrical, column-like structures are the Haversian systems and are laid down in concentric rings called lamellae. Each of these systems is in turn interconnected to other systems to provide a continuous network of blood vessels and nerves. Trabecular bone comprises the majorityof interior long bone tissue, in addition to that of the hip and vertebrae. It is also called "spongy" or "cancellous" bone becaue of its soft, spongy texture. Cortical bone, however, is dense and very hard. It is the second of the two types of bone and forms bone surfaces. Periosteum is the fibrous membrane of connective tissue that snugly covers all bones, but it does not cover articular surfaces (where bones come in contact with each other). The articular surfaces are cofererd with cartilage, which prevents bones from rubbing together. The periosteum also contains attachment sites for musles, ligaments, and tendons. For adults, the periosteum is responsible for forming new bone as a result of injury or infection. And in children, the periosteum is critical to new bone formation, as well as configuring the shape of bone. A Volkmann's canal is one which allows the transmission of blood vessels (or capillaries) from the periosteum into the bone. A nutrient artery is an artery which supplies the medullary cavities of long bones.