The ends and interiors of long bones are composed of an open lattice of bone called spongy bone tissue or marrow. Within this lattice framework, most of the body's red blood cells are formed. Surrounding the spongy bone tissue at the core of bones are concentric layers of compact bone tissue in which the collagen fibrils are laid down in a pattern that is far denser than marrow. The compact bone tissue gives the bone the strength to withstand mechanical forces. New bone is formed by cells called osteoblasts, which secrete collagen fibers on which calcium subsequently is deposited.
Bone is laid down in thin concentric layers called lamellae.
The lamellae are laid down as a series of tubes around narrow channels called Haversian canals, which run parallel to the length of the bone. The Haversian canals are interconnected and carry blood vessels and nerve cells. The blood vessels provide a lifeline to living bone-forming cells and the nerves control the diameter of the blood vessels and thus the flow through them. With that rather pedantic, textbook explanation of bone as a basis, we now can look into what happens to it as a result of exercise. We return to information provided by the New Bolton research.