How does the body maintain bone health: bones are living organs that contain, several tissues (including bone tissue, nerves, cartilage, connective tissue. Bone composition and structure provide strength and flexibility. 65% of bone tissue is make up of many minerals (mostly calcium and phosphorus) that provide hardness. 35% of bone is a mixture of organic substances that provide strength, durability, and flexibility: the most important substance is collagen. The ends of long bones (arms and legs) Inside flat bones (breastbone, ribs and most bones of the skull) The constant activity of bone tissue promotes bone health: bone develops in a series of three processes, bone growth, bone modelling. Continues until early adulthood: bone remodelling. Replaces old bone with new bone to maintain mineral balance. Bone remodelling maintains a balance between breakdown and repair: bone density- the degree of compactness of bone tissue, reflecting the strength of the bones. Other bone density measurement tools: quantitative ultrasound technique.