Bone

Bones!

Bones are amazing parts of our anatomy, they are not dead as you may think, but living tissue that serve critical functions within our bodies.

The outer layer of our bones is known as cortical or compact bone, it is the strong dense calcified tissue, and is for structure and protection.  Cancellous bone is the soft portion of our bones, where the marrow, blood vessels, and connective tissue is located.  

Our bones are made up of both living and non-living material.  The organic portion (20-25%) is mostly collogen, but also has non-collagenous protiens (meaning proteins not made of collagen), and bone cells.  The inorganic portion (70%) is almost entirely mineral called hydroxyapatite.  5% of our bones are made up of water.  Our bones are in a constant state of change.  Microscopically there are cells building and removing bone material.  These are known as osteoblasts, which work to build bone, and Osteoclasts which work to remove it. 

Structurally our bones provide us with protection for our internal organs, support for our body weight, and the impact of movement.

Our bones provide an attachment point for muscles and ligaments.  We utilize them as levers in order to move our bodies in conjunction with our muscles.  They are amazing at adapting to stress and repairing themselves when damaged.

Metabolically they are a reservoir for calcium, phosphorus, and fat.  Within the center marrow of our bones is the formation of our blood cells, known as hematopoiesis.

As stated above our bones are in a constant state of change.  Physical activity, or a lack of physical activity can have an enormous effect on the building and breaking down of our bones, which in turn affects how strong our bones are.  Physical activity increases mineral deposition and collagen production.  It also signals the cells within our bones to build more bone.  A lack of physical activity signals our bones to remove bone without replacing with new bone.  Ideally we have enough physical activity so that our bones are being built at the same rate they are being removed. 

Who knew bones were such an amazing, versatile part of our anatomy!

Our bones grow throughout childhood, until they reach their peak mass at around 18 years old for women, and 20 years old for men. Then beginning around age 40 our bones begin to lose mass. That loss is accelerated sharply in women after menopause. Individual peak bone mass varies from person to person, influencing factors include gender, genetics, and race. As our bone mass declines we become more susceptible to fractures.

Men have an advantage over women in that their bones are wider, and thicker. Men's bones also have an advantage in a process known as periosteal apposition, which is new layers of outer bone is produced. So when men lose bone density from the center of their bones, they have a larger outer layer to compensate.

Genetics can influence peak bone mass by as much as 50-85%. Genetics influences the onset of menopause which typically results in a sharp decline of bone mass. Genetics also influences how your body is shaped, your muscle strength, as well as bone turnover. Different races have different genetic make ups. White and Native American women have the highest fracture rates, and African Americans have the lowest. It is interesting to know that Hispanic and African American women reach their peak bone mass later than white women. And Asian women have greater thickness and density, giving them stronger bones.

Hormones produced by our bodies have a large influence on our bone density. These hormones work to maintain a balance of calcium in our blood, and to promote bone growth.
Parathyroid hormone, and vitamin D work to control our levels of calcium in the blood by stimulating the breakdown of bone, releasing calcium into the blood when needed. Calcitonin works to slow the flow of calcium into the bloodstream when there is an excess by inhibiting the breakdown of bone.

Some of the hormones that have influence over our bone mass are estrogen which stimulates vitamin D activation, while also limiting the breakdown of bone, and enhancing the formation of bone. Estrogen is an important hormone for both men and women. Testosterone has influence of peak bone mass, and increased size of bones. Growth hormone, and insulin-like growth factor are important for increasing bone density, and growth. Thyroid hormone is necessary for growing our bones, but having high levels can promote the breakdown of our bones.

Osteoporosis is a disease of the bones, and can affect both men and women. Our bones are in a constant state of breakdown and rebuilding, Osteoporosis occurs when the rate of breakdown outpaces the rate of rebuilding. This results in lower bone mass, so the bones become porous, weak and susceptible to fractures

Many factors contribute to Osteoperosis, but there are some things you can do to help lessen your risk of developing this disease.

- Regular vigorous exercise is a major factor in the development of strong bones, and in continuing to keep our bone healthy. Not only does exercise increase our bone mass, it also improves our flexibility, muscle strength, and balance which can help prevent falls.  Participating in exercises, such as strength training, that creates stress on our bones is important in the prevention of osteoporosis. 

- Getting adequate amounts of calcium and vitamin D are essential to building and maintaining bone.

-Your overall nutrition is another important factor. Maintaining a healthy balanced diet, including a wide variety of fruits, vegetables, and protein sources.