Combining Three Well-Known Laboratory Exercises to Better Model Kidney Function

Students often find kidney function confusing and somewhat counterintuitive, yet existing lab demonstrations often incompletely explain the process (e.g., by misrepresenting the role of filtration). I show how three easy exercises can be combined to demonstrate water recovery and reuptake of ions, as well as ultrafiltration. Materials are generally inexpensive, available through online resellers, and many are recoverable after lab. I then discuss extensions and limitations to this model.