The document provides instructions for a lab to model the function of kidneys using everyday materials. Students will filter a mixture of gravel, sand, and water through different materials including a wire screen and filter paper to separate particles from water, simulating how kidneys filter waste and toxins from the blood. The lab aims to demonstrate that kidneys remove toxins and other unwanted substances from the blood through selective filtration so the blood stays clean.

1. URINARY SYSTEM
SEVENTH GRADE.
FIRST TERM.
Guided stage.
TOPIC II
FIELD WORK.
How can you model the function of a kidney?
The kidneys filter substances from blood plasma. How can you use everyday materials to model the
function of the kidneys?
1. Read and complete a lab safety form.
2. Label three plastic cups 1, 2, and 3.
3. Mix a small amount of fine gravel and sand with water in cup 1.
4. Place a small piece of wire screen in a funnel and, place the funnel in cup 2.
5. Carefully pour the sand-water-gravel mixture into the funnel. Let it drain. Record your
observations in your Science Journal.
6. Remove the screen. Replace it with a piece of filter paper. Place the funnel in cup 3.
7. Carefully pour the contents of cup 2 into the funnel. Let it drain. Record your observations.
Analyze and Conclude
1. Describe what happened during each filtration.
2. Key Concept Summarize how your filtration systems model the function of the kidneys.
From: iScience Grade 7, Davis County Edition. Page 487.