Table Of ContentT H E A M A Z I N G H U M A N B O D Y
EXCRETORY
SYSTEM
LORRIE KLOSTERMAN
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Marshall Cavendish Benchmark
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Tarrytown, New York 10591
www.marshallcavendish.us
Text copyright © 2010 by Marshall Cavendish Corporation
All rights reserved. No part of this book may be reproduced or utilized in any form or by any
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and retrieval system, without permission from the copyright holders.
All websites were available and accurate when this book was sent to press.
Editor: Karen Ang
Publisher: Michelle Bisson
Art Director: Anahid Hamparian
Series Design by: Kay Petronio
Library of Congress Cataloging-in-Publication Data
Klosterman, Lorrie.
Excretory system / by Lorrie Klosterman.
p. cm. — (The amazing human body)
Includes bibliographical references and index.
Summary: "Discusses the parts that make up the human excretory system, what can go wrong, how to treat those
illnesses and diseases, and how to stay healthy"—Provided by publisher.
ISBN 978-0-7614-4485-5
1. Excretory organs—Juvenile literature. 2. Excretion—Juvenile literature. 3. Feces—Juvenile literature. 4. Urine—Ju-
venile literature.
I. Title.
QP159.K66 2010
612.4'6—dc22
2008037261
This book is not intended for use as a substitute for advice, consultation, or treatment by a licensed medical practitioner. The
reader is advised that no action of a medical nature should be taken without consultation with a licensed medical practitioner,
including action that may seem to be indicated by the contents of this work, since individual circumstances vary and medical
standards, knowledge, and practices change with time. The publisher, author, and medical consultants disclaim all liability
and cannot be held responsible for any problems that may arise from use of this book.
Front cover image: A colored X ray of the kidneys
Title page: Kidney cancer cells
Back cover: A microscopic view of glomeruli in the kidneys
= A microscopic view of the surface of the bladder.
Photo research by Tracey Engel
Front cover photo: David Becker/Getty Images
The photographs in this book are used by permission and through the courtesy of: Alamy: Scenics & Science, 10; Phototake,
26; Bartee Photography, Inc./Phototake, p. 36. Custom Medical Stock Photo: Educational Images Ltd., 24. Getty Images:
3D4Medical.com, 12, 18, 29, 46; Nucleus Medical Art, Inc., 14, 15, 54; Dr. Richard Kessel & Dr. Randy Kardon, 16; Dr. Kessel &
Dr. Kardon/Tissues & Organs, 21; Ralph Hutchings, 28; Dr. Dennis Kunkel, 40; David Becker, 47; Tim Boyle, 56; Jeanene Scott,
59. Photo Researchers, Inc.: James Cavallini, 4; Volker Steger, 23; SPL, 35 (both); BSIP, 38; John Bavosi, 42, 50; Stephen J.
Krasemann, 45; Sam Ogden, 49; AJPhoto / Hôpital Américain, 53; Sheila Terry, 67. Phototake: ISM, 20; Craig Zuckerman, 43.
Shutterstock: Sebastian Kaulitzki, 6; Christina Richards, 7; Antonio Munoz Palomares, 8; Christopher Edwin Nuzzaco, 30;
cardiae, 31; Christina Richards, 34; Jim Barber, 41; gresei, 58; Robyn Mackenzie, 60; Elena Elisseeva, 61; mark cinotti, 63;
Andi Berger, 64; Thomas M. Perkins, 65; Anetta, 68. SuperStock: Image Source, 19, 52. Visuals Unlimited, Inc.: Dennis Kunkel
Microscopy, Inc., 17, 33.
Printed in Malaysia
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CONTENTS
CHAPTER 1
What Is the Excretory System?
. . . . . . . . . . . . 5
CHAPTER 2
The Parts of the Excretory System
. . . . . . . 13
CHAPTER 3
How the Excretory System Works
. . . . . . . . 27
CHAPTER 4
Problems with the Excretory System
. . . . . 39
CHAPTER 5
Caring for Your Excretory System
. . . . . . . . . 57
GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
FIND OUT MORE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
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1
What Is the
Excretory System?
EE
very day, when you get hungry or thirsty, your body is telling you
that it needs something. Hunger is your body’s way of saying that it
needs more food to use as fuel. That fuel keeps you alive and active.
Thirst is a signal that your body needs more moisture inside. Without
the proper amount of moisture, the billions of cells that make up your
body cannot survive. In fact, drinking fluids is more important to
survival than eating food. Most people could live for many days, or
even a few weeks, without food. But nobody can survive for more than
a few days without water.
The excretory system, which is sometimes called the urinary
system, is made up of several organs (shown in yellow).
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EXCRETORY SYSTEM
This diagram shows some of the parts of the digestive system (pink). Waste material from the foods
you eat and drink are processed and eliminated by your digestive system.
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What Is the Excretory System?
Even though foods and beverages are so important, not every last bit of
a meal, or sip of a drink, gets used once it is inside the body. Instead, there
is leftover waste. The body’s waste materials are familiar to everyone.
Things go into our bodies, and things come out.
T WO KINDS OF WA STES
All sorts of words are used to talk about the waste that our bodies make.
Solid waste is called feces. To defecate means to get rid of the solid waste.
The process of doing that is defecation. Liquid waste from the body is
called urine. To urinate means to get rid of liquid waste. The process of
doing that is urination.
Urine is a form of liquid waste, and is made up of chemicals and substances that have been removed
by organs called kidneys.
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WHERE FOOD AND DRINKS GO
Many people believe that solid waste carries the bits of food and drink to all parts
comes from the foods we eat, while liquid of the body—wherever the blood goes. That
waste comes from is how a meal fuels the
beverages we drink. body’s needs.
That is not true. All However, there are cer-
things we swallow tain parts of food that our
go into the digestive bodies cannot break into
system. After pass- pieces very well. That ma-
ing the throat, they terial is called fiber. It gets
go into the stom- pushed along the intes-
ach, and then into tines until it reaches the
the intestines. Along end. There, it collects until
that journey, foods Your body processes and uses all of the food the person feels the urge
and drinks you consume during the course
and beverages are to rid of it by defecating.
of the day. Some parts of the food and drinks
mixed with strong are used to nourish your body, while some is At that point, the waste is
excreted as waste.
chemicals made by called feces. If a person
the stomach and intestines. Those chemi- stops eating for a few days, feces are no
cals, called digestive enzymes, break up longer made.
what we have swallowed into pieces that Liquid waste, or urine, is very different.
are far too small to see with the naked The internal organs that create urine are
eye. The pieces then work their way out not part of the digestive system. Kidneys
of the intestines and into nearby blood continue to make urine all the time, even if
vessels. The blood within the vessels a person stops eating and drinking.
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What Is the Excretory System?
Feces and urine are made and eliminated, or removed, in two very
different ways. Feces are made in the digestive tract. That tract is the
long pathway through which foods and beverages travel after you have
swallowed them. The beginning of the digestive tract is the mouth.
The end is the anus. In between those two are the portions of the tract
called the stomach and intestines. In those places, food and beverages
are changed into microscopic bits that our bodies can use for energy. But
some of what we swallow makes the journey along the digestive tract
without being used. It reaches the end and collects as waste. Whenever
a person feels the need to defecate, the waste—feces—is released into
the toilet.
Urine is made very differently from solid waste. Odd though it may
seem, urine is made from blood. Urine is mostly water—as is blood—but
urine has several kinds of chemicals that the body does not need. The
water and chemicals are taken out of blood by a pair of organs called the
kidneys. These remarkable organs are able to cleanse the blood that passes
through them, and create a liquid waste—urine. All day and all night the
kidneys are at work making urine. Another organ in the body, the bladder,
stores the urine for up to several hours. As the bladder gets full, a person
feels the need to urinate. Urine flows out of the bladder through a tube
that opens to the outside of the body, between a person’s legs.
YOUR PERSONAL PLUMBING
Getting rid of feces and urine is just as important as taking in food
and water. It is like keeping house. You need to bring in supplies for the
household, and you also have to get rid of trash. The body has internal
organs that do these jobs. Getting rid of solid waste is one job of the
digestive system (the digestive tract, plus other organs that are important
in breaking foods into bits). Getting rid of liquid waste is one job of
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