Hands-on Activity: Kidney Filtering
Educational Standards :
Learning Objectives (Return to Contents)
After this activity and accompanying worksheet, students should be able to:
Materials List (Return to Contents)
Each group needs:
To bind the screens for safety:
Introduction/Motivation (Return to Contents)
To which human body system do the kidneys belong? The excretory ─ or urinary system! This is an important body system because it helps us remove any harmful substances from our body. The kidneys actually work as a filtering system for our blood. They take blood in from the bloodstream, remove waste products (such as salt, minerals and any toxins, or bad stuff) and combine them with water. Then the body gets rid of this water and waste combination, known as urine. The kidney, in a healthy adult, can process as much as 45 liters of water a day, releasing only 1-2 liters in the form of urine.
Engineers have designed many amazing filtering systems. They have designed systems to filter bad stuff out of water so that people can have clean water to drink, which helps us stay healthy. They have designed filters to remove bad particles from the air, so we can have clean air to breathe. They have even designed filters to prevent extra noise from coming through on our phones. Engineers also design special filters for people in the hospital or who have medical problems. Many of the machines that you see in a hospital have been designed by engineers.
Sometimes people have kidneys that do not work well, so engineers have designed a special machine, called a dialysis machine, which filters their blood when their kidneys can not. A dialysis system removes a person's blood through a tube, runs it through filters to remove wastes and extra fluids, and then returns the clean blood to their body. It is a truly amazing system! The dialyzer consists of thousands of small fibers. The blood runs through the fibers, and a cleansing solution runs along the outside of the fibers. The solution acts like a sponge, and it soaks up the extra fluid and waste from the blood. The dirty solution is discarded, and the clean blood gets returned to the body.
Today we are going to test some filter materials and decide which ones work best for removing objects from water. Although these filter models are larger than an actual kidney, they help us investigate how kidneys filter waste from our blood. Also, the model allows us to understand how engineers can design filters to create dialysis machines for people whose kidneys are not working properly.
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
Before the Activity
With the Students
Attachments (Return to Contents)
Safety Issues (Return to Contents)
Be careful when handling the sharp edges of the mesh screening.
Troubleshooting Tips (Return to Contents)
Use a large enough container to contain the poured water.
Assessment (Return to Contents)
Vocabulary: Have students write down the terms kidneys, excretory system, ureters and bladder under the Vocabulary section of the Filtering System Journal. Have them discuss with a neighbor what these terms mean and write short definitions next to the terms.
Activity Embedded Assessment
Worksheet/ Observations: Explain to students that engineers and scientists record their observations while they are working with a model. Using the Filtering System Journal, ask them to write down anything they noticed during the activity in the "Observations" section of their journal, and any questions they might have in the "Questions I Have" section. Review their answers to gauge their mastery of the subject.
Discussion: Lead a discussion out loud, asking students what they have learned about filters and engineering. Have students write down the things they have learned in their Filtering System Journal under the "What I've Learned" section. Make sure to answer any questions the students may have written in the "Questions I Have" section of their journal.
Math Extension: Have students work through the Filtering Worksheet. Remind students that there are numbers that engineers would need to know in order to size a dialysis machine properly.
Activity Extensions (Return to Contents)
Have students research engineering systems that use filters (water treatment systems, waste water treatment systems, etc.) Remind students that many engineered systems actually are designed with knowledge that engineers have learned through science and nature.
Invite a medical technician to speak to the class about dialysis machines.
Activity Scaling (Return to Contents)
For upper grades, explain more of the details of how a dialysis machine works. Some students may have a friend or relative who is or has been on dialysis. Talk about what qualities are important to consider when designing a dialysis machine (sterility, work as similar to the body's function as possible, comfort level of the patient, ease of use for the patient and nurse/aide, etc.). Check out http://kidney.niddk.nih.gov/kudiseases/pubs/hemodialysis/ for more information on dialysis. Have students complete the challenge section of the math worksheet.
For lower grades, discuss why we use the filters in order of largest to smallest mesh size, and not the other way around. Talk with students about how in mathematics and in many engineering applications ─ (as well as in life!) ─ the order in which we do things is very important. Doing things in the correct order helps us achieve and understand the outcomes of a model. The math worksheet may not be appropriate for students under 3rd grade.
References (Return to Contents)
U.S. Department of Health and Human Services, National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), NIH Publication No. 06–4281, March 2006, "Prevent Diabetes Problems: Keep Your Kidneys Healthy," http://diabetes.niddk.nih.gov/dm/pubs/complications_kidneys/ - accessed May 24, 2006.
U.S. Department of Health and Human Services, National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), NIH Publication No. 03–4666, September 2003, "Treatment Methods for Kidney Failure: Hemodialysis," http://kidney.niddk.nih.gov/kudiseases/pubs/hemodialysis/ - accessed May 19, 2006.
ContributorsJessica Todd, Emily Weller, Sara Born, Abigail Watrous, Denali Lander, Malinda Schaefer Zarske, Janet Yowell
Copyright© 2006 by Regents of the University of Colorado
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0226322. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.
Supporting Program (Return to Contents)Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder
Last Modified: March 7, 2014