Introduction
Everybody knows that some organs in the human body are necessary for survival: you need your brain, your heart, your lungs, your 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.
Cleaning Up
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). About 400 gallons (1,514 liters) of recycled blood are pumped through the kidneys every day! Then the waste is collected out of the blood by tiny filters inside the kidneys. These filters are called nephrons, and they are so tiny they can only be seen with a high-powered microscope! There are over a million nephrons inside each kidney.
The waste that is collected combines with water (which is also filtered out of the kidneys) to make urine (pee). As each kidney makes urine, the urine slides down a long tube called the ureter (say: yur-uh-ter) and collects in the bladder, a storage sac that holds the urine. When the bladder is about halfway full, your body tells you to go to the bathroom. When you pee, the urine goes from the bladder down another tube called the urethra (say: yu-ree-thruh) and out of your body.
The kidneys, the bladder, and their tubes are called the urinary system. Here's a list of all of the parts of the urinary system:
* the kidneys: filters that
take the waste out of the blood and make urine
* the ureters: tubes that carry the urine to the bladder
* the bladder: a bag that collects the urine
* the urethra: a tube that carries the urine out of the body
Keeping a Balance
The kidneys also balance the volume of fluids and minerals in
the body. This balance in the body is called homeostasis (say:
hoh-mee-oh-stay-sus).
If you put all of the water that you take in on one side of a scale and all of the water your body gets rid of on the other side of a scale, the sides of the scale would balance. Your body gets water when you drink it or when you drink other liquids. You also get water from some foods, like fruits and vegetables.
Water leaves your body in several ways. It comes out of your skin when you sweat, out of your mouth when you breathe, and out of your urethra in urine when you go to the bathroom. There is also water in your bowel movements (poop).
When you feel thirsty, your brain is telling you to get more fluids to keep your body as balanced as possible. If you don't have enough fluids in your body, the brain communicates with the kidneys by sending out a hormone that tells the kidneys to hold onto some fluids. When you drink more, this hormone level goes down, and the kidneys will let go of more fluids.
You might notice that sometimes your urine is darker in color than other times. Remember, urine is made up of water plus the waste that is filtered out of the blood. If you don't take in a lot of fluids or if you're exercising and sweating a lot, your urine has less water in it and it appears darker. If you're drinking lots of fluids, the extra fluid comes out in your urine, and it will be lighter.
What Else Do Kidneys Do?
Kidneys are always busy. Besides filtering the blood and balancing
fluids every second during the day, the kidneys constantly react
to hormones that the brain sends them. Kidneys even make some
of their own hormones. For example, the kidneys produce a hormone
that tells the body to make red blood cells.
Now you know what the kidneys do and how important they are. Maybe next Valentine's Day, instead of the same old heart, you can give your parents a special card featuring the kidneys!
Disclaimer: This information is not intended be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.
Updated and reviewed by: Laszlo
Hopp, MD
Date reviewed: January 2004
Originally reviewed by: Steven Dowshen, MD