The diaphysis is the middle section of a long bone, which is hollow and contains the bone marrow and adipose material. The diaphysis is only found on long bones. This type of bone is covered with periosteum, which has an osteogenic layer that helps with appositional growth prior to maturity.
The diaphysis is the longest part of a long bone. The tubular bone formation connects to epiphyses, located on each end of the long bone. Along with these two parts, the long bone also has disks shaped areas called the epiphyseal disk or plate. The ends of the long bones, the epiphyses, are coated with cartilage.
The periosteum that covers the long bone is very important when it comes to the growth of bones and the repair of them after an injury. The periosteum is made up of collagenous fibers and cell. These cells are called osteoblasts, which help remove bone fragments and blood debris so that fibroblasts can enter a break in the bone and begin knitting it back together. When a long bone is done growing, the ends of the bones go from being hollow bone sections, to being filled with spongy bone. This spongy bone helps absorb impact between the bones when running or walking.