Getting Started

What keeps us from flopping to the floor like a rag doll? What functions do our bones perform besides protecting our organs. Why are some of our bones big while others are very small and delicate?

Do you know how many bones we have? Name some functions of these different bones. What is our largest bone and what is our smallest? What do you think is the most important bone we have? Why?

Overview

Like a house, the human body has a framework. But instead of wood, the body's framework is made of all the bones in our skeletal system. There are long bones (arms and legs), short bones (fingers and toes), flat bones (skull and sternum), and even tiny bones (in the middle ear). Some bones, like the ribs, permit respiration and protect vital organs such as the heart from harm. Others, like the spinal vertebrae, form the framework to keep us upright as well as surround and protect the spinal cord.

Unlike a house's framework, however, the body's framework is alive - bones are living tissue. From birth until mid- to late- adolescence, bones grow as we do. They reshape themselves throughout our lives. Some of the bone cells that carry on this growth and "remodeling" work are called osteoblasts and osteoclasts. Bones grow at special areas called growth plates.

The outer layer of hard "compact" bone (the cortex) consists of a system of tunnels that looks like a miniature collection of hollow pipes. These tunnels keep bones lightweight, yet provide the strength necessary to support the body. The tunnels also allow for the exchange of nutrients and waste products. Collagen, a protein, gives bones their elasticity while calcium salts make them hard. Bone marrow, located in the center of our long bones, makes blood cells.

To develop properly and grow strong, our bones need calcium, vitamin D, and regular exercise. Sources of calcium such as milk, yogurt, ice cream, and broccoli provide the nutrients for continuous bone building and remodeling. Vitamin D helps our bodies absorb this calcium through the gut. Vitamin D comes either from a chemical action of sunlight on our skin or from fortified milk. Finally, regular exercise makes bones stronger by stressing them. When bones are stressed, they respond by fortifying themselves. This cycle of stress and response to stress promotes strengthening.

When we don't get enough calcium, vitamin D, and exercise, our bones deteriorate. For example, young children who are deprived of calcium and vitamin D may develop a type of bone weakness called rickets. Older people, particularly women, may develop a form of weak bones called osteoporosis.

Prevention of bone weakness is crucial - once weakness occurs, it may not be reversible. So to have healthy bones and keep our body's living framework strong and supple, we must eat foods containing calcium every day, exercise on a regular basis, and get either a moderate amount of exposure to sunlight or drink milk fortified with vitamin D.

Connections

1. What contributes to making and keeping bones strong?
2. What would happen if bones didn't grow or stopped growing too soon?
   What are some ways to help with this problem?

Resources

Baldwin, D. & Lister, C. (1984) You and your body: The structure of your body.
New York: Bookwright Press.

Dineen, J. (1988) How our bodies work: The skeleton and movement.
Englewood Cliffs, NJ: Schoolhouse Press, Inc.

Getting calcium without the fat.(1996, May) Consumer Reports, pp. 48 - 49.

Parker, S. (1994) How the body works. Pleasantville, NY:
The Reader's Digest Association, Inc.

Optimal calcium intake:
http://isis.nlm.nih.gov/nih/cdc/www/97txt.html

Nation Dairy Council
10255 West Higgins Rd Suite 900
Rosemont, IL 60018-5616
(800) 426-8271

Main Activity

Scary. Creepy. Weird. Cool. That's what you may say about skeletons on Halloween. Now you can easily make one in your classroom. Close your eyes and think of yourself as a skeleton. Imagine all your bones from the top of your head down to your toes. Did you know that when fully grown, you will have 206 bones in your body?

Materials

• poster board
• brads, medium and small
• glue
• scissors
• tape measures
• metric conversion charts
• anatomy book illustration of
  skeletal system
• chalkboard and chalk
• string

1. On the chalkboard, list the names of all the bones you want to include when you make your skeleton. Copy the list on paper.

2. Next, take measurements of all the bones on your list, using yourself as a model. Write measurements next to the appropriate bone on the list.

3. Either working in a small group or individually, start drawing your bone pieces on your poster board, using your measurements. Label all your pieces so you will know which are which. Then, cut out the pieces. Finally, connect the various bones using brads or glue.

4. When you have completed your skeleton, insert a string near the top of its head and hang your masterpiece in the classroom.

Questions

1. What things did you notice about your skeleton that are different from the real you? How could this skeleton move?
2. What did you notice about the bone sizes? Where are big bones? Little ones? Why?
3. What do the brad connectors and your joints have in common? Why is it necessary to use brads for joining some bone but not others?

Bring clean, dry chicken bones to class. Place half the bones in a bowl with a lid and cover them with vinegar. Place the remaining bones in a similar bowl and cover them with water. Cover the bowls. Check the bones daily for ten days. What effect did the different solutions have on the bones? Why?

Ask a radiologist or orthopedic surgeon from a local hospital to bring in some bones or portions of a skeleton as well as some x-rays used to examine bones. X-rays of broken bones would be especially interesting.

Discuss the daily calcium needs of a 16-year-old athlete in training. Design a one-day diet that would meet her or his daily calcium requirements as well as all other nutritional needs. What are all the things you have to consider in planning this diet? What percentage of calcium is needed in it? What types of foods provide calcium?