Support and Protection
Bones provide the structure for our bodies. Otherwise we would be mainly limp bags of skin! (yuck!) Our bones give our bodies shape. Have you ever heard someone say that so-and-so's face has great bone structure? Or that someone else is big-boned? Our bones provide shape to who we are.
Our bones also protect our bodies. For example, if someone were to be punched in the chest (my Mom loves boxing, so I used that example), there would not be any damage to their lungs or heart. That's because our rib cage protects our thoracic cavity organs. Similarly, our pelvic girdle protects most of our reproductive organs. In addition, our vertebral column protects our spinal cord and our skull protects our brain; if someone "breaks their back," no one is worried about the bones, but instead people are worried about the loss of protection to that person's spinal cord. This last point reminds you that your bones are not foolproof-- and for that reason humans are often seen to wear seat belts or helmets when doing dangerous things (like going faster in a car than we could ever go on foot, or zooming along on a motorcycle or rollerblades).
The only reason that our muscles can work to move our bodies is that they are attached at their ends to bone (via tendons). This way, when a muscle shortens, it affects bone positions, and our bodies are seen to move.
Figure 7.13 and the text in Hole go farther into this topic than I care to. I would like you to understand that bones act as levers, and that joints are the fulcrums (pivot points) about which they move. I would also like you to understand that the force that acts to create the movement may be either a muscle or an outside perturbation (like someone else who shakes your hand). But the details of a first-, second-, and third-class lever are unnecessary.
Blood Cell Formation
Blood cells are made wherever their precursor cells are. These cells (you'll have to learn next semester that they are called hemocytoblasts) are found in red marrow in adults. Red marrow is simply a loose connective tissue that contains these blood cell precursors and the cells that they are making. It is red, like the red blood cells it makes, because red blood cells contain the protein hemoglobin which is a red pigment protein.
Early on in our lives, most of our bones contain red marrow. It is slowly replaced by yellow marrow as we get older, so that we only have enough red marrow to meet our needs in blood cell production. Yellow marrow is simply a fat storage area.
Inorganic Salt Storage
For those of you who had a hard time with the chemistry material you had to learn, this may be a bit more difficult to understand-- even though it is very simple. Inorganic salt storage is also a very important function of bone.
© 2011 STCC Foundation Press