The kidneys

Imagine a road that leads out of a town. The road can be used by anyone: cars, trucks, bikes, even roller-skaters and horses travel on it. But here the road becomes a motorway, where not everyone is allowed to drive. Vehicles that are supposed to be there are allowed to carry on, but everything else has to take a different road. In this way traffic remains safe and efficient.

Police officer Nephron makes sure of that! The blood system is like a huge system of highways. All the traffic in there needs to run smoothly too. There are special organs in your body which take care of that. Two of them are located behind the lower ribs near the spine.

They are: the kidneys! Most people have two kidneys. They look a bit like large, brownish beans, about the size of a fist. Each kidney consists of a million tiny filters called nephrons. The nephrons separate waste from the bloodstream, and remove it.

But how does this work? Your blood carries important nutrients and oxygen. But there are also other things in the blood that your body doesn’t need. Some of these are poisonous and dangerous. All substances travelling in your bloodstream enter the kidneys through the renal artery.

They are then pushed through this dense network of tiny nephrons. Blood cells and proteins are too big to get through, so they go back to the bloodstream.. ..along with everything else that the body might still need.. ..such as minerals, sugars, amino acids, and some water. The rest is a waste substance which is called urea. Mixed with water and unnecessary salts, urea forms a liquid called urine, or as you might call it: pee. Urine leaves the kidneys through two narrow tubes connecting the kidneys to the bladder.

These are called ureters. When your bladder fills up with urine, you start to feel like you need to go to the toilet. When you pee, all the extra water and salts - along with the other unwanted substances - leave your body through another tiny tube: the urethra. An adult produces up to one and a half litres of urine every day, most of which is water. The kidneys however, do much more than remove waste from your body.

They are in charge of traffic control! They make sure that: there are enough blood cells to carry oxygen in your blood, that water and minerals are in balance, and that your blood pressure is right. If the kidneys are so important to us, what happens if they don’t work as they should? Then, we have a problem! Things are going where they shouldn't go, and things that should be there can't get through.

It’s getting dangerous! The good thing is that most people have two kidneys, so that one of them can always take over the work from the other. The traffic in our bodies can move around as it should because our kidneys, just like Police officer Nephron, are doing their job!