A nephron combines filtration with selective transport. Its glomerulus filters water and small dissolved substances from blood while retaining cells and most large proteins. Along the tubule, reabsorption returns much of that filtrate to circulation. Other substances can be secreted into the tubule. The final remaining fluid contributes to urine.
The human body · Discover & try
What stays in blood, and what becomes urine?
Reading level 3 of 5 · IndependentChange
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Nephron
A kidney unit containing a filter and tubule.
Reabsorption
Returning a filtered substance to blood.
Watch · Try · Explain
See how it works
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A simplified nephron route map. Particle counts do not represent real filtration rates, concentrations or individual kidney function.
What to look for
- Compare a blood cell with glucose.
- Notice the route back to blood.
Explain what you noticed
A large protein approaches the normal filter in this model. Which route is most appropriate?
Keep this idea: Kidneys filter fluid, then selectively return and remove substances before urine leaves.
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Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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