Life is Solid (Bone)

Why do I have bones and where do they come from?

Bone is a solid connective tissue containing calcium that is vital for human life.  There are over two hundred bones in your body.  The bones provide support and protection from external injury for many important organs. The skull protects your brain and the vertebrae protect your spinal cord and your ribs and breast bone protect your heart and lungs. Deep inside your bones is the marrow tissue that makes your blood cells (red blood cells to carry oxygen, white blood cells to fight infection and platelets to prevent bleeding).  Your bones are shaped differently in relation to their function and are attached to each other by ligaments to form your different joints.  Your upper body has shoulders, elbows, wrists and finger joints and your lower body has hips, knees, ankles and toe joints.  Your muscles are attached by tendons from one bone to another, spanning across these joints, and when they contract this allows you to move around and handle things.  There are also joints between the vertebrae in your spinal column, both ends of your ribs and your jaw and temporal bone so you can open your mouth to talk, chew and yawn.  Finally, there are three tiny bones (ossicles) in each ear which allows you to hear.  But that’s not all that your bones do for you.  Your body’s ability to live and work properly (clotting and nerve, heart, skeletal muscle and gland function) depends on it having the right amount of calcium in your blood and your bones fulfill this need by acting as a reservoir for its calcium needs.  But how does your body get calcium in the first place and then how does it make your bones?

Nobody ever tells us to be sure we take in enough sugar or salt.  In fact we're usually told to be careful not to take in too much or else we'll get fat and develop diabetes or high blood pressure.  That's because our gastrointestinal system readily absorbs all the sugar and salt we bring in.  But that isn’t the case for calcium.  Calcium is a mineral that’s present in foods like milk products, eggs, nuts, fruits and green leafy vegetables.  However, without vitamin D our gastrointestinal system can only bring in about ten percent of the calcium it receives which isn’t enough for us to live.  Vitamins are chemicals your body usually doesn’t produce but are needed nonetheless for certain metabolic reactions and so must be obtained from the diet.  When exposed to sunlight your skin helps your body to make its own vitamin D.   But medical science has shown that, although vitamin D is naturally present in certain types of fish, mushrooms and eggs, since deficiency can lead to significant debility and even death, supplements in fortified foods such as milk, orange juice and cereals are needed to keep you healthy.  However, what most people don't realize is that the vitamin D we make ourselves and bring in from our diet can’t help in the absorption of calcium from the gastrointestinal system until it becomes activated.  It must first travel in the blood to the liver and then the kidneys where certain chemicals are added to it so it can become calcitriol (activated vitamin D).  Calcitriol then travels to the intestine and helps it bring in about thirty percent of the calcium from a normal diet and up to ninety percent from a calcium-deficient diet.

Bone is formed by living cells that contain organic material and minerals.  There are mainly two types of bone cells involved in the formation, growth, and turnover of bone.  These cells actually live within the bone and are surrounded by tissue fluid with calcium in solution.  To make bone the osteoblast lays down a firm organic mesh, called osteoid, which is made up of protein.  It then takes some of the calcium from the surrounding bone fluid and mineralizes the osteoid by depositing calcium crystals into it.  It’s the calcium in your bones that gives them the strength to withstand the forces of nature.  The other bone cell is the osteoclast which reverses what the osteoblast does by removing calcium (and placing it back into the surrounding bone fluid) and the osteoid from the bone. Although bone is a very solid and rigid material, it nevertheless has a very dynamic metabolism.  All of the bones in your body continually undergo a process of bone turnover called remodeling.  This involves the osteoclasts breaking down the bone followed by the osteoblasts building it back up again.  The remodeling of bone usually involves anywhere from five to twenty percent of your body’s total bone mass each year.  It is thought to allow your skeleton to adapt to changes in mechanical stresses like weight-bearing and multi-directional movements, which take place with activities of daily living.  A person who leads a very sedentary life or is forced to remain in a chair or bed for prolonged periods of time may lose significant amounts of bone mass.  In fact, as a result of prolonged weightlessness in space, loss of bone mass has been shown to take place in astronauts who have not undergone exercise programs.  Despite its present knowledge of what happens during bone remodeling, medical science has a very limited understanding of what factors control this process 
     
Finally, about ninety-nine percent of the calcium in your bones is in crystalline form.  Being a solid, the calcium within these crystals is not available to the rest of your body.  The remaining one percent of the calcium inside your bones is dissolved as calcium phosphate in the bone fluid that surrounds the bone cells.  This bone fluid is in direct contact with your capillaries and is therefore also in communication with the rest of your body by way of your circulation.  It’s by way of the capillaries and the bone fluid that your body can supply your bones with the calcium they need as well as what it needs to live and work properly.  This is how your bones act as a reservoir for the calcium needs of your body. 

Three Questions for Mr. Darwin (Sir Charles)

  1. How did my body anticipate the need for my over two hundred bones and place them exactly where they’re needed so I can move around, handle things, talk, chew and yawn?

  2. How did my body know that to bring in enough calcium from my intestine it would not only need enough vitamin D but that it would first have to activate it by way of its liver and kidneys and where did the information come from to teach these organs what to do?
  3. Which came first, the osteoblast or the osteoclast and where did the information come from to tell them what they’re supposed to do, how fast and when?

Also see Dr. Glicksman's Series on

"Beyond Irreducible Complexity"

"Exercise Your Wonder"


Howard Glicksman M. D. graduated from the University of Toronto in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario and Spring Hill, Florida. He now practices palliative medicine for a Hospice organization in his community. He has a special interest in how the ethos of our culture has been influenced by modern science’s understanding and promotion of what it means to be a human being.

Comments and questions are welcome.

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