The arm bones of a weight lifter will be thicker and heavier than that of a runner because of the role of bone remodeling. Mineral turnover, the process where bones are recycled and replaced through the balanced activity between osteoblasts and osteoclasts, is essential for the body to be able to adapt to new environmental stresses. Bones being utilized more frequently, such as arm bones in a weight lifter, will become thicker, stronger and develop denser surface ridges. Runners do not use their arm bones as frequently as weight lifters and as a result, their bone development in the arms is not subjected to the same stimulation as weight lifters to increase bone remodeling.
As we observe a given a sample of long bone that shows concentric layers surrounding a central canal, we are observing the basic functional unit of compact bone, or the osteon, also known as the Haversian system.
Within each osteon are concentric circles (formed by calcified matrices called lamellae) comprised of osteocytes (bone cells). Lamellae-formed concentric circles surround a central canal containing one or more blood vessels and function to provide nutrients to (and remove waste materials from) osteocytes via diffusion with blood vessels.
In a long bone, the shaft is called the diaphysis while the expanded portions at the ends are called epiphyses.
The diaphysis, or the shaft of the lone bone, is formed by compact bone (or dense bone). Spongy bone, consisting of bony rods and is spacious compare to compact bone, forms the epiphyses, or the ends of the long bone.
The ends of long bones are called epiphyses and as they are comprised of spongy bones, the lamellar arrangement is different in that there are no osteons. Conversely, compact bones contain osteons. As a result, the sample of long bone showing concentric layers surrounding a central canal is from the shaft of the bone and not the end of the bone.
As bone forms throughout the human skeleton, they develop to accommodate other tissues and organs from tendons and ligaments to nerves and blood vessels. Such formations result in external and internal features on the surface of the bone. Surface features on the bone are known as bone markings and are characterized and described as follows:
• Elevations and projections
• Bumps formed where tendons and ligaments attach
• Bumps or elevations formed for articulation with adjacent bones