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