New Blood Cells Are Made Inside Your Bones

Bones do more than hold you up. The National Institute of Arthritis and Musculoskeletal and Skin Diseases, part of the U.S. National Institutes of Health, explains that some types of bone have a jelly-like material inside called bone marrow, and that new blood cells are made inside the bone marrow. Making blood is not the only extra job. Bones can store minerals like calcium and phosphorus, and release them when the body needs them. They are made mostly of a protein called collagen and a mineral called calcium phosphate, which together make bones strong and flexible. Bones also change with use. According to the institute, when you are young, new bone is made faster than old bone is broken down, and bones respond to exercise by making new bone tissue.