How does the excretory system work?

Every day you get rid of about 1 kg of carbon dioxide, a litre and a half of urine and a surprising amount of sweat. The body gets rid of waste four ways: urine from the kidneys, carbon dioxide from the lungs, sweat from the skin and stool carrying bile from the liver.

Read how it works: How does the excretory system work? · The history of understanding excretion · More boxes on Glassbox

Chapters in this interactive model

1. Four ways out: Urine, breath, sweat and stool: five organs share the job of getting rid of waste.
2. What you throw away every day: Carbon dioxide, urea, bile pigment, salt and water, and the exit each one takes.
3. Turning poison into urea: Protein leaves nitrogen behind as ammonia. The liver locks it safely into urea.
4. Hold on: the bladder and your brain: A stretchy bag, two gates and a brain that says “not yet” until you are ready.
5. Sweat or urine: balancing with the weather: The same water has to leave somehow. Heat sends it out through the skin; cold sends it to the bladder.
6. When the exits have trouble: Infections, stones, dehydration, bedwetting and the prostate, and when to see a doctor.