Activity 4B: Race for the Pure: Blood Cleansing in the Kidneys Topic: Blood Part of: Unit: Cast Your Net: Adventures with Blood

Entire Activity Download (15 pages)

Individual Downloads

• Teacher Background Information
• Teacher Administrative Information (TEKS)
• Teacher Kidney Façade
• Student Information Pages
• Student Data Page
• Student Processing Out

Keywords

kidney, kidney model, diabetes, high blood pressure, kidney function

Search Curricular Keywords

Key Concepts

basic structure and function of the kidney

Process Skills Utilized

differentiating between structure and function; utilizing a model to interpret the natural world; exploring the relationship between structure and function in living organisms

Intended Grade Levels - 6 - 8

Objectives

Utilizing a model, students will be able to:

• Explore the structure and function of the kidneys
• Discuss the limitations of the kidney model used in this activity
• Explain why the function of the kidney is so important
• Explain how diabetes and high blood pressure affects kidney function

Activity Description

Students will race against a simulated kidney in filtering toxins from simulated blood.

Activity Materials (per group of 3)

Kidney Model:

• 1 - 3 minute egg timer with kidney façade (paper cut out of kidney, provided at the end of this teacher section, to be taped to face of the timer)
• 1- stopwatch

Filtering Materials:

• 1 - colander with large enough slots to allow “nitrogenous wastes” (rice and birdseed) to pass through but not “blood cells”
• 1 - bar magnet enclosed in a Ziplock® bag
• 1 - 250 ml clear containers (clear plastic cups work well) to hold the filtered toxins
• 1 - large bowl (e.g. cheap plastic salad bowl) to control spillage of the filtering activities. The very thin, inexpensive type works best as it can be flexed to form a lip for pouring the materials.

Blood Model Containing Toxic Materials*

• 1000 ml graduated cylinder to hold the “blood” mixture. (A 2 liter plastic soda bottle can substitute, just cut off the top then measure and mark 1000 ml level with a permanent marker)
• “Red Blood Cells” = 700 ml volume of red kidney beans
• “White Blood Cells” = 200 ml volume of white lima beans

Note: The ratio of red blood cells to white blood cells in the blood is actually about 700:1. The ratio in the graduated cylinder/kidney model is not accurate but necessary to illustrate the presence of white blood cells visually to the students. See extension activity # 2.

• “Nitrogenous Wastes” (urea and creatinine) = 100 ml volume of white rice (creatinine) and 100ml volume of white millet (urea)
• “Drug” = 20 ml volume iron filings (coarse, unoiled)

Note: The “toxin” particles fill in the small spaces between the “blood cells” to make a total volume of 1000ml. You may need to slightly adjust the volumes of the “toxin” particles depending on the size “blood cell” particles you use.

• 1 Class set Student Information Page
• 1 Copy Student Data Page per student

Note: This activity uses only dry materials, so the blood serum is not represented. This is a limitation of this model and should be discussed with students.

Activity Management Suggestions

Assign tasks to each group member. (One student will measure time with the stopwatch and record while the other two manage the filtering. Have students rotate positions with each successive race).

Have several extra “Blood with Toxins” set up in the graduated cylinders/soda containers in case a group spills theirs. This allows them to get right back into the game.

Allow as much student discovery as possible by allowing students to figure out how to use the different tools to filter the substances as quickly as possible.

Allow enough time for each group to “re-race” so everyone has the opportunity to succeed and have a turn at timekeeping and filtering.

Extensions

1. The chart in the Teacher Background indicates the amount of O delivery and blood flow rate to various organs. This illustrates the kidney’s predominance in both these categories. The rates are in ml/min per 100 grams of organ. Students can research or be provided with the average masses of the various organs so they can determine/calculate the approximate blood flow/oxygen delivery to their various whole organs. Students can then generate a new data table with the information they have calculated.

2. The ratio of red blood cells to white blood cells in the blood is actually about 700:1. The ratio in the graduated cylinder/kidney model is not accurate but necessary to illustrate the presence of white blood cells visually to the students. This model does not include the other components of the blood, e.g. plasma and platelets. This is a good opportunity to discuss the limitations of scientific models utilized to represent the natural world and how the application of a particular model determines what components are emphasized or deemphasized. Canvass students for ideas for alternative ways to model blood with its various components and discuss different applications e.g. a model for teaching medical students vs. one to inform patients with blood disorders. Students can research or be provided with the various components of blood then challenged to create models of same while at the same time identifying and discussing the limitations and possible applications of their own models.

3. Point out that the volumes of the components making up the blood and toxin mixture sum to more than 1000ml (1120 ml) yet when added together the volume is 1000ml. Have students hypothesize how this could happen and use the opportunity to discuss how smaller molecules fit into the spaces between larger molecules just like the seed and rice do with the beans.

4. Data from the data tables can be graphed and variables that affected the students’ cleansing time can be discussed and compared to variables that affect the kidney’s cleansing time e.g. blood flow constriction due to decreased cardiac output etc.

5. Students can research kidney diseases and apply them to the model and process out their findings.

Activity References Used

National Institutes of Health
http://www.nlm.nih.gov/medlineplus/ency/imagepages/1101.htm

National Kidney Foundation http://www.kidney.org/

Renal Blood Flow – Glomerular Filtration Rate, George N Coritsidis, MD, Stony Brook University Medical Center http://www.uhmc.sunysb.edu/internalmed/nephro/webpages/Part_A.htm

National Institute of Diabetes and Digestive and Kidney Disease http://kidney.niddk.nih.gov/kudiseases/pubs/kdd/

Nemours Foundation sponsored website “Teen Health”, an excellent source for students written in their language at their level http://www.kidshealth.org/teen/your_body/body_basics/kidneys.html

Comprehensive clinical nephrology. Richard J. Johnson, John Feehally. London ; New York: Mosby, 2000. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Blood.html

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