5.- EXCRETORY SYSTEM: THE KIDNEYS
KIDNEYS? Absolutely. Even though you won’t find a Valentine’s Day card with a kidney on the cover, the kidneys are every bit as important as the heart. You need at least one kidney to live!
Kidneys normally come in pairs. If you’ve ever seen a kidney bean, then you have a pretty good idea what the kidneys look like. Each kidney is about 5 inches (about 13 centimeters) long and about 3 inches (about 8 centimeters) wide — about the size of a computer mouse.
To locate your kidneys, put your hands on your hips, then slide your hands up until you can feel your ribs. Now if you put your thumbs on your back, you will know where your kidneys are. You can’t feel them, but they are there. Read on to find out more about the cool kidneys.
One of the main jobs of the kidneys is to filter the waste out of the blood. How does the waste get in your blood? Well, your blood delivers nutrients to your body. Chemical reactions occur in the cells of your body to break down the nutrients. Some of the waste is the result of these chemical reactions. Some is just stuff your body doesn’t need because it already has enough. The waste has to go somewhere; this is where the kidneys come in.
First, blood is carried into the kidneys by the renal artery (anything in the body related to the kidneys is called "renal"). The average person has 1 to 1½ gallons of blood circulating through his or her body. The kidneys filter that blood as many as 400 times a day! More than 1 million tiny filters inside the kidneys remove the waste. These filters, called nephrons (say: neh-fronz), are so small you can see them only with a high-powered microscope.
If you’ve ever wondered where pee comes from, this movie has the answer!