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. Read on to find out more
about the cool kidneys.
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). The
average person has 1 to 1 1/2 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
(nephrons) remove the waste. Nephrons (say:
neh
-fronz) are so small you can see them only with a high-powered
microscope.
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
-ih-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!
Reviewed by:
Steven Dowshen, MD
Date reviewed: March 2007
Originally reviewed by:
Laszlo Hopp, MD
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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