Human Body Unit - Week 12 - Kidneys and Bladder

Week 12: We built a model of the kidneys and bladder.

Urea arrives at the kidneys from the liver containing blood, waste and water. It is their job to filter it and send the waste onto the bladder for removal from the body. David Macaulay's The Way We Work was our reference book for this project.

First we made urea by mixing lentils to represent the blood, water and yellow food coloring.

We used a clothes rack to hold up the parts of our system. The kids tied two water bottles with the ends cut off to the frame to represent the arteries carrying urea from the liver to the two kidneys.

The three parts of the kidneys; Cortex, Medulla, and Pelvis were represented by the colander, yogurt container and funnel. Both the Cortex and Medulla filter blood. Holes were poked into the bottom of the yogurt container so it would also function as a sieve.

Waste exits the kidneys via the pelvis. In our model the pelvis was a funnel. A plastic bag was taped to the bottom of the funnel to function as the bladder. A straw was poked through the bottom of the plastic bag and taped into place to function as the urethra. The kids pinched the straw in two places to stop the flow of urine. They were the internal and external sphincters.

After the set-up was complete, urea was poured into the kidneys.

It collected in the bladder. The blood (lentils) was collected in the Cortex and Medulla (colander and yogurt sieve) for use elsewhere in the body.

Once the sphincters were relaxed the bladder let loose into the potty.

Our other human body projects are easy to find on the Science Page.

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