Journeys: Kidneys. Stop 1

The sieve

Where does wee come from? Let's find out! We are in a kidney. This little ball of blood vessels works like a sieve. Shake it left and right!

Small things seep through the walls of the ball. Water, salt, sugar and rubbish go through, and the red cells stay in the blood.

You have two kidneys, near your back, a little above your belt. Each has about a million tiny sieves like this.