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Would you believe it?Bones are a living tissue…
[mis à jour le 17 October 2006 à 15h22]
The architecture of our bodies is based on the bone framework, but this is not a fixed, definitive structure as one might think. Our bones evolve throughout our lives, keeping the traces of certain events. Our skeleton is a living thing! And while it enables us to stand up, it also has other more unexpected functions that are essential for our health.
It all starts very early on… From the 4th week of pregnancy, the first ossification points appear on the embryo’s future vertebral column. Hence the name vertebrate inherited by human beings. Up until the 6th week, however, the foetus’ skeleton still only consists of cartilage. This is a tissue that is both resistant and elastic, containing a large amount of water. Hence its almost translucent appearance. This cartilage known as conjugation cartilage is found only in the foetus.
Its role at this stage is to separate the body of the bone (diaphysis) from its extremity (epiphysis) to permit the bone to grow in length. It is gradually replaced by hard bone as the child grows. A different type of cartilage is found in adults, in the ear auricle and nose, for instance, and also in joints where the cartilage tissue facilitates the rotation of the bones. Because of its flexibility and smooth appearance, this cartilage acts as a “buffer” between bony elements, preventing them from wearing out.
The growth of the skeleton is regulated by a hormone secreted by the hypophysis or pituitary gland. When the bones are mature, their centre becomes empty. The marrow, surrounded by a layer of cancellous bone, begins to form. The outside consists of a sheath of harder compact bone which protects everything.
Ossification requires various elements, the best known indeed being calcium, which ensures that the bone is hard and solid. It is transformed into calcium phosphate, a mineral component representing 65% of the finished bone. Hence the importance of ensuring a calcium-rich diet throughout life and during pregnancy.
Balance, in every meaning of the word!
The human skeleton consists of 206 bones. It enables us to stand up and also protects our most fragile organs, such as the brain and lungs. The more bones we have, the greater our dexterity. For instance, the hand contains 26 small bones linked to each other and controlled by muscles and tendons. They allow us great freedom of movement and a good balance when we are on our feet.
The bones also play a chemical role as they help to detoxify the body. The blood vessels they contain eliminate certain heavy metals. The marrow found in some bones (the humerus and femur, the flat bones of the skull, the vertebrae, the ribs, the sternum and the hip) produces blood cells: red globules, white globules and platelets. In the case of anaemia caused by iron deficiency, the marrow no longer produces enough red globules, and this leads to chronic fatigue and other disorders.
And that’s not all! Our bones function like reservoirs: 99% of calcium in the body is concentrated in the skeleton. The body uses this reserve by resorption, depending on its needs. Calcium is necessary for the contraction of our muscles, the transmission of the nerve impulses and the coagulation of the blood. Permanent recycling is carried out to enable this to be done.
Cells penetrate the old bone to remove calcium, while other ones replace the missing cells with new tissue that will calcify. This balance is regulated by vitamin D and hormones, such as the growth hormone, calcitonin and parathormone. Sex hormones slow down bone deterioration.Please note: this is a living tissue!
When calcium needs are high, the bone supplies the part that the diet cannot cover. This is what happens when a woman is pregnant or breastfeeding. The bone density is then temporarily weakened. After the child is weaned, however, bones return to normal density within a few months.
The bone is a living tissue which is constantly changing depending on the life period. Specialists in fact talk about bone tissue. One-quarter of its weight consists of water, organic matter (for instance, a protein named ossein) and mineral salts (calcium, phosphorus and magnesium). It also contains small amounts of fluoride, chloride and potassium.
Nerves and blood vessels are also found in it. The latter transport new red globules to the rest of the circulatory system. They also supply the bone with calcium and vitamin D.
Even after reaching maturity, the skeleton does not remain the same throughout a lifetime. Between the ages of 25 and 35, our bone capital is at its zenith. But there may be considerable variations depending on our lifestyle. Smoking reduces the absorption of calcium, for instance. It therefore speeds up bone loss, and is a risk factor in osteoporosis.
Practising a sport regularly increases bone mass. However, a long period of inactivity will reduce it. In the event of fractures, the damaged bone engages in repair work autonomously, re-establishing a layer of bone substance. To facilitate and direct this re-calcification properly, plaster is placed on the broken limb after having “reduced” the fracture. In other words, after having put the bone parts back into place either manually or surgically… Once it is immobilised, the bone will knit properly.
A lowering of the production of sex hormones by the testicles in men and the ovaries in women signals the decline of bone mass. As we age, an imbalance emerges. The process of resorption of the bone occurs at a rhythm that increasingly accelerates while rebuilding of bone slows down. That is why fractures heal much more slowly in an old person than in a teenager!Where there is a bone, there is a solution
Bone reserves tend to diminish with age. After the menopause, bone loss is multiplied with age. Since the skeleton is no longer protected by hormonal activity, its density gradually diminishes: this is osteoporosis, a disease which affects four out of every ten women. The bone loses its qualities, becomes more fragile and can fracture when there is a slight shock or even just spontaneously.
The parts of the body most affected are the wrist, the vertebrae and the hip. Several signs should alert you. If your mother had an osteoporosis fracture, if you experienced early menopause, if you have taken a cortisone-based medicine for at least three months, if you notice that your height has fallen by over 4 cm and, of course, if after a minor fall you suffer a fracture that should only occur after a very violent trauma…
After having watched his mother lose her autonomy because of fractures caused by osteoporosis, Guy Marchand, a famous French actor and singer, is campaigning against this disease voluntarily, alongside his wife. Honorary President of the association Fracto Sud (an association which deals with osteoporosis in the Provence region), he no longer wants to see women break like glass for no reason: “Because the elegance of women is based on the skeleton. They must be able to maintain their gait and their deportment even when elderly”.
It is a question of dignity, but also a matter of life and death. Because these fractures often have dramatic consequences: physical and moral pain, disablement, loss of height, reduction in pulmonary capacity and, above all, death. The disease cuts ten years off life expectancy!
Fortunately, it is no longer a fatal disease. We now have osteodensitometry to detect osteoporosis or simply the risk of seeing the disease emerge. It is a simple, painless examination but one that is still not covered by health insurance in many countries !
Effective treatment can stop or limit bone loss, as well as strengthen the quality of the bone in order to avoid fractures. This can be done as the disease is setting in. As Guy Marchand points out: “The danger starts early on. It must be anticipated”. He is right. Bones can make us suffer in many ways. And suffer badly because the bone tissue is filled with nerve fibres and blood vessels.
Good bones before even sleeping in the cot! It is possible to prepare for the future as of the first few days of life and even long before! To give a baby a good start in life, pregnant women should follow certain rules such as ensuring a calcium-rich diet and, of course, avoiding cigarettes! It has in fact been proven that the children of mothers who smoke are 1.5 cm smaller and have a weaker bone capital.
To ensure good ossification, breastfeeding is strongly recommended by the WHO, for at least the first six months. For while there is not a large quantity of calcium in breastmilk, it is absorbed better by the infant’s body: 67% compared with 25% for cow’s milk!
A diet rich in calcium and mineral salts afterwards will maintain solid bones. Calcium is found mainly in milk and dairy products, but is also present in mineral water, almonds, fruit and vegetables, and sardines… that is why a varied diet is essential! Open air and sunshine (but not excessive) will help synthesise vitamin D, which is vital to ensure that the bones absorb calcium.
Later on, take care not to make your child walk too early. His still immature skeleton will seek support in different ways that may result in certain malformations as he grows. However, if your baby develops quickly and is trying to walk, do not prevent him! Do not force him to stand on his legs before one year if he is not showing any signs of wanting to walk.
A sport that is practised moderately and regularly will improve the cartilage system and bone framework. It prevents the emergence of arthrosis. An aerobic sport will encourage bone formation and increase the bone capital, for instance cycling, swimming, aquagym, stretching exercises, walking and body-building. There’s something for everyone!
In conclusion, any kind of exercise is good, but moderation is essential. Excessively intensive and violent sport can lead to cartilage injuries. Worse still: when pushed to extremes, as in the case of top-level athletes, sport can block hormone production. Periods stop and a few years later, there is a risk of osteoporosis. These are the famous “fatigue fractures” from which our sports stars suffer… Follow these simple rules and you will maintain good bones at every age. So do not deprive yourself! Because you must work to keep your skeleton in good shape…
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