If you're seeing this message, it means we're having trouble loading external resources for Khan Academy.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Urinary system introduction

8 videos
1 skill
If you want to learn more about the renal system, then urine the right place! (Pun aside, the kidneys are about more than just making urine). Every thirty minutes, your kidneys filter the entire blood supply in your body. Imagine a dirty pool filled with algae. Placing a filter in this pool will cause the algae to be flushed out, and after a time you’ll have a clean, crisp blue pool to enjoy. Just like the filter for a pool, our kidneys filter the blood and remove toxic wastes. These paired organs are key to maintaining electrolyte and water homeostasis in your body.

Meet the kidneys!

VIDEO 6:24 minutes


VIDEO 9:33 minutes

The kidney and nephron

VIDEO 18:38 minutes
Overview of how the nephrons in the kidney filter blood and reabsorb water and other molecules.

Secondary active transport in the nephron

VIDEO 14:13 minutes
Secondary Active Transport in the Nephron

Introductory urinary system quiz

Introductory renal quiz