BioEd Online

Teacher Background

Internal skeletons, or endoskeletons, must be strong enough to support a body against the pull of gravity. They also must be light and flexible enough to allow easy movement. Endo­skeletons meet all these requirements by connecting bones of different shapes and sizes (flat, irregular, long, short) that provide support, allow freedom of move­ment, and protect many of the body’s most vital internal organs.

With only a few exceptions, like the tailbone in humans, each bone fulfills a particular need. The skull protects the brain and sense organs (eyes, nose, mouth and ears). A flexible spine encloses and protects the spinal cord—the main highway for messages from the brain to the rest of the body. The rib cage surrounds the lungs, heart and other internal organs. Four limbs (arms and legs in humans) are joined to the spine via broad flat bones (shoulder blades and hip bones). Arms, legs and wings contain some of the longest and strongest bones in vertebrates. More than half of the 206 bones in the adult human body can be found in the limbs.

Vertebrate skeletons are comprised primarily of cartilage and bone. Cartilage is firm, but flexible. The skeletons of most embryos are made of cartilage, which gradually is replaced by a harder material—bone. Bone is living tissue that changes in response to exercise and use.

Objectives and Standards

Concepts

• Endoskeletons are made of connected bones inside a body.

• Bones provide support for the body.

Science, Health and Math Skills

• Observing

• Comparing and contrasting

• Inferring

Materials and Setup

Teacher Materials

• Overhead projector

• Transparency of "Head-to-Toes" page

Materials per Group of Students (see Setup below)

• Clear container with straight sides that holds at least 1 liter of water (or a glass aquarium in a central location)

• Food coloring

• Paper towels

• Plastic zip-top bag, snack-size

• Water

• Copy of the student sheet

Setup

1. Obtain and cook enough chicken pieces to provide one or more different bones (any size or shape) to each group of students. You also may have students bring leftover cooked chicken bones from home.

2. Remove all meat from the bones (additional boiling may be necessary), and soak the bones in a 1:10 bleach/water solution for five minutes.

3. Allow the bones to dry before using them in class.

4. Have students work in groups of four.

5. Save the bones to use with the activity, “What Are Bones Made Of?” or dispose of them.

Safety

Please read “Setup & Management” (above) and follow all school district and school laboratory safety procedures. It always is a good idea to have students wash hands before and after any lab activity.

Procedure and Extensions

1. Remind students of the skeletons they constructed in the activity, “Skeletal Structures.” Ask, What kind of skeleton do vertebrate animals have? (animals with backbones, or endoskeletons) What are some examples of vertebrates? (fish, birds, reptiles, amphibians, mammals)

2. Distribute cleaned chicken bones.

3. Direct the groups to observe the bones carefully with and without their magnifiers. Ask questions to promote careful observations, such as, What color are the bones? Are the bones as hard as rock? Does the surface texture vary along the length of the bone? (Students may be able to observe that the ends of some bones are porous, while other parts are smooth.) Can you see softer parts (cartilage) attached to any of the bones? (Ribs, for example, will have flexible cartilage tips.)

4. Have each student make a detailed drawing or written description of a single bone. Challenge students to think about where the bones they observed would be found in a chicken’s body. Discuss their observations.

5. Make a class list of the similarities among the different bones observed. Follow by making a list of the differences.

6. Give each student a copy of the “Chicken Bones” page and have students identify the bones they observed. Ask, Were you able to predict the location of the bones you observed? What helped you decide where the bones would be found?

7. Next, prompt students to think about the human skeleton. Ask, Do you think human skeletons are very different from chicken skeletons? Why or why not? Make an overhead transparency or give each student a copy of the “Head-to-Toes” page. Have students compare the drawing of the human skeleton to the drawing of the chicken skeleton and identify similarities and differences.

8. Using context clues from the poem, help students fill in the appropriate names for the major bones of the body. You may want to have students read the poem aloud or write additional verses.

9. Discuss the human skeleton with students. Have them notice that bones are precisely arranged with bilateral symmetry. Point out that we have pairs of bones. Ask, Why is this structure a good design for us to maintain balance? Did anyone build an unsymmetrical skeleton? (See “Skeletal Structures” activity.) Help students understand that the symmetrical skeleton provides balance and potential for mobility.

Handouts and Downloads

Download color images from The Science of Muscles and Bones Teacher's Guide.