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- Focus:
There is a relationship among the structure of bones, bone mineral density, and the strength of bones. This lesson will help students understand these relationships and recognize how the strength and density of bone can reduce fractures.
Activities | Introduction | Objectives | Resources & Web Sites
Activities
| Activity 4A: Applying the Density Formula |
(calculation, density formula, density, mass, volume) |
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| Activity 4B: Determination of Bone Density with Bone Specimens |
(density, observation, graphing, volume, mass, bone, specimen preparation, trabecular bone, cancellous bone, calculation, mean, median) |
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| Activity 4C: Magnified Examination of Bone Sections |
(bone, cancellous bone, observation, trabecular bone, specimen preparation) |
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| Activity 4D: Figuring Fracture Rates |
(fracture rate, calculation, population statistic)
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| Activity 4E: Graphing Fracture Rates |
(fracture rate, graphing, coordinate point, risk factor, inference) |
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| Entire Lesson Download (23 pages) |
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Introduction
Lesson 4, "Bone Density" extends the knowledge of bone anatomy in lesson 3 to an understanding of bone function. The central physical science concept of "density" is taught by using bone mineral density as an example. After an introduction to the formula for calculating density, students directly measure volume and mass of serial bone specimens in a group class activity. Students should observe that the ends of bone are less dense (more trabecular bone) than the shafts (cancellous bone). This lab also reinforces the mathematical concepts of mean, median, and range introduced in the Embracing Diversity Unit. The last two activities of this lesson are math and graphing exercises relating age to hip fractures. Students will use numerators (the number of fractures) and denominators (the years of exposure), to calculate fracture rates for men and women at different ages. These rates are graphed in two lines (one for each gender) and students are asked to interpret the results. The central observation is that hip fracture risk increases with age for both men and women. However, fracture rates are much higher for women than men. Challenge students to ask "Why?" The primary reasons are that (a) bone mass and density decrease with age, and (b) women, on average, have lower bone mineral densities than men. The strength of bone and its ability to resist fracture is directly related, in large part, to its mass and density.
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Objectives
Students will be able to:
- Calculate density - mass (in grams) per unit volume (in milliliters).
- Examine bone specimens for density and micro-structures.
- Calculate fracture rates.
- Graph and interpret line graphs
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Resources & Web Sites
Fracture Rates Around the World http://courses.washington.edu/bonephys/mapfxs.html
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