The Backbone
The backbone is not just a simple bone. It really consists of a series of bones, one fitting snugly on top of another. Each of these small bones is called a vertebra. The vertebrae are hollow, permitting the spinal cord to pass through them. Most people have thirty-three vertebrae. Some people have one or two more, however.
Between the vertebrae thick pads of cartilage are found. These give the backbone a certain amount of springiness, acting as cushions when you jump or sit down hard. Even walking jars the body somewhat. For with even step the body is raised a bit and then set down again. Such shocks are not very severe, but on a busy day you may take thousands of steps. The cartilage shock-absorbers between the vertebrae are very helpful in keeping the vertebrae from jarring one another.
Measure yourself carefully some morning-a Saturday morning would be best- just as soon as you wake up. Then, after you have been busy all day, walking and running about, measure yourself again in the evening. You may in for s surprise; it is likely that during the day you have grown shorter by as much as one half to three quarters of an inch. Every step you took during the day packed the cartilages a little, so that each of them because slightly thinner and more compact than it had been. Do not worry about this, for the next morning you will be as tall as ever.
Strong ligaments hold the vertebrae in line, keeping them from slipping out of place. A vertebra may be wrenched out of place in an accident, however. When a severe strain is put on the backbone, the ligaments may not be strong enough to hold the vertebrae in place. One or two of them may slip a little, and you have a sprained back.
The Ribs
Twelve pairs of ribs are attached to the backbone. They protect the heart and lungs from injury. Ten pairs of these ribs are joined also to the chest bone in the front of the body by means of ligaments. The lowest two pairs of ribs are not so attached in front; for that reason they are often called “floating ribs”. The gives them a chance for more movement when you breathe than is possible for the other ribs. You can find them at the bottom of the chest if you feel for them at your side. Floating ribs are shorter than other ribs.
When you breathe, the ribs and chest bone is raised. This gives the lungs more room, so that air passes into them. The lungs expand, filling the extra room made by the raising of the ribs and chest bone. Then the ribs are lowered again, and air is forced out of the lungs. Such movement of the ribs takes place from twelve to twenty times every minute. If you have been exercising violently, or working very hard, this rate of breathing may be much higher.
May increase your knowledge!
Thank you very much. . .
“Gerald S. Craig and John Urban”,
Professor of Sciences
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