Bones and Their Disorders

Our musculoskeletal system is a complex network of bones, muscles and joints. These components, along with tendons, ligaments, and cartilage, work together to allow us the freedom to move about and do practically anything we please.

Bones, although very light, are strong enough to support our entire weight. From our heads to our toes, bones provide support and help form our shape. The skull forms the shape of our face, but more importantly, the skull protects the brain. The backbone, or spinal column, protects the spinal cord. The ribs form a cage that shelters the heart, lungs, liver and spleen, and the pelvis helps protect the bladder, intestines, and the reproductive organs in women.

The adult human skeleton has 206 bones. Our bones begin to develop before birth, and at birth, a baby’s body has about 300 bones. Baby’s bones are made of flexible cartilage, but within a few weeks, the process of ossification begins. Slowly but surely, bones are fused together and cartilage is replaced by hard deposits of calcium phosphate and stretchy collagen, the two main components of bone. This ossification process takes approximately 20 years; at age 25, the bones are as big as they will ever be.

Bone growth may stop there, but bone building continues throughout life. Bone contains three types of cells:

• Osteoblasts: make new bone and help repair damage
• Osteoclasts: break down bone and help to sculpt and shape it
• Osteocytes: carry nutrients to and waste products from blood vessels in the bone

Through the function of these cells, the bones’ living tissue is constantly renewed and reshaped. Despite this constant renewal, bones can develop problems. There are many different kinds of bone problems:

• Fracture or broken bone is common and can happen because of falls, sports injuries, or accidents. Osteoporosis can also cause a fracture. Overuse can cause stress fractures, which are small cracks in the bone.
• Osteoporosis makes the bones weak and more easily broken. It is a silent disease; you may not know you have it until you break a bone. Anyone can develop osteoporosis, but it is most common in older women.
• Osteogenesis imperfecta (OI) is known as brittle bone disease and is caused by a defect in a gene. OI causes weak bones that break easily, sometimes for no known reason. OI can also cause other problems such as brittle teeth, weak muscles, and hearing loss. Approximately 20,000-50,000 people in the U.S. have OI.
• Paget’s disease, also called osteitis deformans, is a disease that causes the bones to grow larger and weaker than normal. The disease might affect one or several bones, but not the entire skeleton. The most common bones affected are the spine, pelvis, skull and legs. The cause of Paget’s disease is unknown, although in some cases, a virus could be responsible. About one million people in the U.S. have Paget’s disease. It is most common in older people and more men than women are likely to have the disease.
• Cancer beginning in a bone is rare; it more commonly spreads to the bone from another part of the body. There are three types of bone cancer:
1. Osteosarcoma which develops in growing bones, usually between ages 10 and 25
2. Chondrosarcoma starts in cartilage, usually after age 50
3. Ewing’s sarcoma that begins in nerve tissue in bone marrow of young people, usually after treatment with radiation or chemotherapy
• Other bone diseases caused by poor nutrition, genetic factors or problems with rate of bone growth or remodeling

There are some things that happen to our bones which we have no control over. However, we can control our diet, exercise and unhealthy habits. Keep bones strong by eating a diet rich in calcium and vitamin D, incorporate weight-bearing exercise into your daily schedule and avoid smoking and excessive alcohol.