Cycle of formation and breakdown of bone tissue

Even in an adult person, the bone tissues undergo the process of constant recycling. The new tissue is usually built at the same rate as the breakdown of the old one. This is achieved by the fact that cells within the bone tissue are going through the process of maturation. Using the analogy of the human life, the babies would be called preosteocytes. To translate that to English, pre means that they are not finished yet, osteo means bone, and cyte means cell.

Those then mature into an adult cell (or person in analogy), called osteocyte, literally meaning the cell of the bone. Those then differentiate into two possible types called osteoblasts and osteoclasts. The former type build new bone tissue, and the later one breakdown of the old tissue.

The flow diagram above shows the whole process nicely in cyclical manner. The vicious cycle is not really that vicious, as it's essential for life and the health. But it indirectly points out that it's going on for the duration of whole life. The old, worn-out tissue  then would be the equivalent of the pensioner (in the analogy). Still important and functioning in certain ways, but sooner or later to be broken down into the separate components, representing the death.

The bone tissue serve a number of functions, one of them is storage, and retrieval system of calcium and phosphorus, along with some other minerals. The form in which those two are stored is the called the calcium phosphate. Calcium is also used as the substance that initiate the muscle contraction (see my other post describing this process), along with some other functions.

If the working speed of osteoblasts and osteoclasts are the same, the same amount of calcium phosphate remains inside of bones. This system is so precise that even the lack or excess of dietary calcium and phosphorus won't affect it. The excess is simply excreted, and the lack is covered by slightly slowing down of osteoblasts, and slightly speeding up of osteoclasts. All this effort is important for keeping the blood levels of calcium and phosphorus within the narrow and healthy range.

The only way to increase the amount of stored calcium phosphate in bones is via vigorous muscular activity, just like the only way to decrease it is via the of the use of muscles. That's why bed-ridden patients show significant reduction in the bone density within months, which can be then reversed by subsequent activity or sport - as it's demonstrated by many athletes and body-builders.

Also, the increase and decrease in bone density goes hand in hand with the increase and decrease of the volume of the muscle tissue. One without the other is not possible, along with many other improvements and declines of efficiency in other tissues and organs throughout the body. The heart efficiency, lung's maximum volume/capacity, the amount of hemoglobin in the blood, total amount/length of blood vessels, total amount of body fat, and the production of certain hormones - would be only a few examples.

So as you can see many processes within the human body are linked and directly influence each other. Pretty basic fact, but quite  fascinating too. The human body is just so full of wonders, so never stop wondering and pondering. See you in next post.