Bone is a living tissue that supports our muscles, protects vital internal organs, and stores most of the body's calcium. It consists mainly of a framework of tough, elastic fibers of a protein called collagen and crystals of calcium phosphate mineral that harden and strengthen the framework. The combination of collagen and calcium phosphate makes bones strong yet flexible to hold up under stress.
Bone also contains living cells, including some that nourish the tissue and others that control the process known as bone remodeling. Throughout life, our bones are constantly being renewed by means of this remodeling process, in which old bone is removed (bone resorption) and replaced by new bone (bone formation). Bone remodeling is carried out through the coordinated actions of bone-removing cells called osteoclasts and bone-forming cells called osteoblasts.
During childhood and the teenage years, new bone is added to the skeleton faster than old bone is removed, or resorbed. As a result, bones grow in both size and strength. After you stop growing taller, bone formation continues at a faster pace than resorption until around the early twenties, when women and men reach their peak bone mass, or maximum amount of bone. Peak bone mass is influenced by various genetic and external, or environmental, factors, including whether you are male or female (your sex), hormones, nutrition, and physical activity. Genetic factors may determine as much as 50 to 90 percent of bone mass; environmental factors account for the remaining 10 to 50 percent. This means you have some control over your peak bone mass.
After your early twenties, your bone mass may remain stable or decrease very gradually for a period of years, depending on a variety of lifestyle factors such as diet and physical activity. Starting in midlife, both men and women experience an age-related decline in bone mass. Women lose bone rapidly in the first 4 to 8 years after menopause (the completion of a full year without a menstrual period), which usually occurs between ages 45 and 55. By age 65, men and women tend to be losing bone tissue at the same rate, and this more gradual bone loss continues throughout life.
Our bones support us and allow us to move. They protect our brain, heart, and other organs from injury. Our bones also store minerals such as calcium and phosphorous, which help keep our bones strong, and release them into the body when we need them for other uses.
There are many things we can do to keep our bones healthy and strong. Eating foods rich in calcium and vitamin D, getting plenty of exercise, and having good health habits help keep our bones healthy.
But if we don’t eat right and don’t get enough of the right kinds of exercise, our bones can become weak and even break. Broken bones and fractures can be painful and sometimes need surgery to heal. They can also cause long-lasting health problems.
But the good news is that it is never too late to take care of your bones.
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