To help teach students about the importance of bones and bone mass, we’ve developed this teacher resource and activity to use in the classroom. This article and activity originally apeared on wardsci.com.

When most people think of bones, they tend to think of inert, rigid components that make up the skeleton, and not much else. Actually, bones are quite alive and every bit as dynamic as other organs in the body. In addition to providing an internal support for the body, bones also allow for locomotion, protect internal organs, produce blood cells, store and regulate calcium levels, and remodel by breaking down old bone and replacing it with new bone.

Bone remodeling is controlled by a complex mix of hormones and chemical factors, which balance the activity of two types of bone cells, osteoblasts (bone-forming cells) and osteoclasts (bone-resorbing cells).

• Osteoclasts dig holes into the bone, releasing the small amounts of calcium into the bloodstream that are necessary for crucial body functions, such as muscle contraction, nerve function, and blood clotting.
• Osteoblasts then rebuild bone by first filling in the holes with collagen and then by laying down crystals of calcium and phosphorus.

These cells continually remodel bone as part of the cyclical process that enables bone to change its physical and metabolic characteristics over time. When we are young, bone is built at a much faster rate than it is broken down, resulting in skeletal growth. By the time we reach the age of 30 or so, bones are as dense as they will ever be. After that time, as a normal part of the aging process, bone is broken down at a faster rate than it is created, thus resulting in a reduction of bone mass. Once the process begins, females experience bone deterioration at a rate nearly three times as rapid than do males. All too often, however, the amount of calcium present in the bones decreases to the point where the bones become brittle and are prone to fracture. Once this state has been reached, osteoporosis is diagnosed.

Osteoporosis

Osteoporosis has been described as a geriatric disease with an adolescent onset. This statement emphasizes the importance of regular exercise and a healthy diet beginning at a young age in order to reduce the effects of the disease in later years. Bones that are subjected to weight-bearing exercise become thicker and stronger, whereas bones that are inactive become thin and brittle. Surprisingly, these skeletal changes can occur after a relatively brief period of time. For example, if a leg is broken and becomes unused, it will only take a few weeks for the injured leg to lose approximately a third of its bone mass. However, these bones will rebuild equally as quickly when normal leg use resumes.

The entire bone remodeling process is dependent on a diet providing adequate amounts of calcium and phosphate as well as the absorption and transportation of these minerals to sites of bone formation. Since we excrete calcium every day, we must replace it daily to avoid having it taken from our bones and weakening them over time. Good sources of calcium are dairy products, dark green leafy vegetables, foods fortified with calcium, or dietary supplements. But, calcium alone cannot build bone. Vitamin D is also needed to help absorb the calcium. This nutrient is naturally produced by our skin when its exposed to sunlight, but it can also be obtained from dietary supplements and fortified foods such as milk products and orange juice.

Other than diet and exercise, there are also a number of other factors that can affect your chances of developing osteoporosis. Some of these factors can be controlled, but others cannot. For instance, you can also lower your risk of developing this disease by not smoking and by not consuming excessive amounts of alcohol. However, certain factors beyond your control will actually increase your chances of getting osteoporosis. Included in the list are: aging, being female, having a naturally small-boned frame, being a Caucasian or Asian woman, being post-menopausal, and the prolonged use of certain medications. Interestingly, though, even if many of these factors apply to you, you may never develop osteoporosis, but it is also possible to develop the disease even if none of these factors apply. The best bet is to error on the side of caution and take the steps necessary to reduce your chance of getting this debilitating disease later in life.

Activity

Here’s a simple and fun activity you can do to illustrate the crucial role calcium plays in obtaining strong bones. It’s a great way to actively engage your students in a discussion about bones. If you have never tried this experiment before, you may be surprised at the results!

Materials:

• White vinegar
• 2 Chicken bones
• 2 Jars with lids

Procedure:

1. Clean two chicken leg bones until they are free of meat and cartilage or “gristle” and let them dry overnight.
2. Place one bone in a jar and completely cover it with vinegar. Seal the jar tightly with a lid and label it “vinegar”.
3. Place the remaining bone in the empty jar and completely cover it with water. Seal the jar tightly with a lid and label it “water”.
4. Let the bones soak for 3 days and remove them.
5. Rinse the vinegar-soaked bone with water and compare the properties of each bone.

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