Human Body Encyclopedia

HumanBody
Encyclopedia

A DORLING KINDERSLEY BOOK

LONDON, NEW YORK, MUNICH, Contents
MELBOURNE, and DELHI
Human body
Senior editor Penny Smith
Senior art editor Cheryl Telfer 4-5 Your amazing body
6-7 What makes you you?
Editors Ben Morgan, Zahavit Shalev 8-9 Building blocks
Additional design Jacqueline Gooden, 10-11 Organizing the body
Tory Gordon-Harris, Claire Patane, Laura Roberts
Skeleton and bones
Illustrator Peter Bull
Digital illustrator Pilar Morales 12-13 Skeleton
14-15 Head case
Consultants Dr Penny Preston, Dr Frances Williams 16-17 Bendy backbone
18-19 Living bone
Publishing manager Sue Leonard 20-21 Bone and cartilage
Managing art editor Clare Shedden 22-23 Moving joints

Jacket design Victoria Harvey Moving muscles
Picture researchers Marie Ortu, Rob Nunn
24-25 The body’s muscles
Production controller Shivani Pandey 26-27 How muscles work
DTP designer Almudena Díaz 28-29 Muscle power

First published in Great Britain in 2005 by Brain and senses
Dorling Kindersley Limited
30-31 Headquarters
80 Strand, London WC2R 0RL 32-33 Network of nerves
34-35 Touchy feely
A Penguin Company 36-37 Taste and smell
38-39 Look out!
2 4 6 8 10 9 7 5 3 1 40-41 How we see
42-43 Eye to brain
Copyright © 2005 Dorling Kindersley Limited, London 44-45 Listen here
46-47 Balancing act
All rights reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without the prior

written permission of the copyright owner.

A catalogue record for this book
is available from the British Library.

ISBN 1-4053-0848-6

Colour reproduction by Colourscan, Singapore
Printed and bound in China by Toppan

Discover more at

www.dk.com

2 Test yourself with the questions at the bottom of each page...

LONDON, NEW YORK, MUNICH, Contents
MELBOURNE, and DELHI
Human body
Senior editor Penny Smith
Senior art editor Cheryl Telfer 4-5 Your amazing body
6-7 What makes you you?
Editors Ben Morgan, Zahavit Shalev 8-9 Building blocks
Additional design Jacqueline Gooden, 10-11 Organizing the body
Tory Gordon-Harris, Claire Patane, Laura Roberts
Skeleton and bones
Illustrator Peter Bull
Digital illustrator Pilar Morales 12-13 Skeleton
14-15 Head case
Consultants Dr Penny Preston, Dr Frances Williams 16-17 Bendy backbone
18-19 Living bone
Publishing manager Sue Leonard 20-21 Bone and cartilage
Managing art editor Clare Shedden 22-23 Moving joints

Jacket design Victoria Harvey Moving muscles
Picture researchers Marie Ortu, Rob Nunn
24-25 The body’s muscles
Production controller Shivani Pandey 26-27 How muscles work
DTP designer Almudena Díaz 28-29 Muscle power

First published in Great Britain in 2005 by Brain and senses
Dorling Kindersley Limited
30-31 Headquarters
80 Strand, London WC2R 0RL 32-33 Network of nerves
34-35 Touchy feely
A Penguin Company 36-37 Taste and smell
38-39 Look out!
2 4 6 8 10 9 7 5 3 1 40-41 How we see
42-43 Eye to brain
Copyright © 2005 Dorling Kindersley Limited, London 44-45 Listen here
46-47 Balancing act
All rights reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without the prior

written permission of the copyright owner.

A catalogue record for this book
is available from the British Library.

ISBN 1-4053-0848-6

Colour reproduction by Colourscan, Singapore
Printed and bound in China by Toppan

Discover more at

www.dk.com

2 Test yourself with the questions at the bottom of each page...

Heart and blood Reproduction and growth

48-49 Blood flow 94-95 Making a baby

50-51 Boom boom 96-97 Growing in the womb

52-53 All about blood 98-99 Double trouble

54-55 Blood cells Life cycle
56-57 Bumps and cuts
58-59 Hormones 100-101 The early years
102-103 Growing up
Lungs and breathing 104-105 Growing older

60-61 Air bags Keeping healthy
62-63 Air and oxygen
64-65 Making sounds 106-107 What’s in food?
66-67 Ah-choo! 108-109 Sleep
110-111 Doctors and dentists
Skin, nails, and hair
Communication
68-69 All wrapped up
70-71 At your fingertips 112-113 Body language
72-73 Fairly hairy 114-115 Use your hands
116-117 Express yourself 
Fighting disease
Reference section
74-75 Germs
76-77 Body defences 118-119 Amazing facts about YOU!
78-79 Fighting germs 120-121 Through the ages
80-81 Allergies 122-123 Glossary
124-127 Index
Digestive system 128 Acknowledgements

82-83 Digestive system

84-85 Chew it over Coloured discs contain
 facts about special topics,
86-87 From mouth to stomach Circles show such as taste.
88-89 Inside the intestines close-up images
Brain and senses Taste and smell
Urinary system you might not
otherwise be able Taste and smell Different tastes Runny nose Your nose
There are five types of tastes When you have a cold, tiny and mouth
to see. We need to eat and drink to  – bitter, sour, salty, sweet, hairs in your nose get clogged are linked at
survive, but taste and smell and umami. with mucus. This stops them the throat.
are what make these everyday
activities so enjoyable. Bitter foods, suchas wafting smell particles deep into
coffeecanbebadfor you. your nose and makes it difficult
Taste detector Most poisons arebitter. to smell – and taste – things.
Your tongue is a big muscle covered
90-91 Waterworks in clusters of taste buds. Each cluster Sour foods includelemon Sensitive nose
recognizes a particular kind of taste. andvinegar. Foodthat Much of what we
92-93 The stretchy bladder has“goneoff”tastessour. think of as taste is

Salt detecting tastebuds actually smell.
canbefoundon thelips The back of your
as wellas onthe tongue.
nose is linked to
“Get into it” activity Sweet foods naturally your mouth so
attract us. Our first food you can smell
buttons show you how  –milk – is sweet. your food as
you chew it.
Umami is thesavoury
Bitter Sour tasteoffoodslikesoy n o s es can re  c  o    g  n   i   z     
Sour
sauceandmushrooms.    S  o  m e e   

you can try things Salt     b   u d s a re cramme   d      , 1    
0     
Sweet 0      

out for yourself.  g e t i nt o  i t     0      

Try putting       s  t  e 0      
sugar on different places    a  d       
on your tongue. It tastes        t
sweeter in some places    e fif               
Salt      0   n  er 
than others. Now try      0   t 
salt, lemon juice,       0
and coffee.    ,        m s
  .   s  l  l    e  
       0 

           1

Taste buds

Saliva in your

mouthdissolves    e . Smell receptors
your food. The food Special cells deep inside your nose
washes over tiny taste     g  u 
buds between the bumps o n t o y o  u  r t  o   n recognize scent particles floating
in the air. These cells link
on your tongue. Taste buds directly to your brain.
recognizedifferentflavours.
37
36  .  s  e r t i l i l l  i  m   0  0  5  1  -  0  0  0 1
How much saliva does an average person produce in a day?

About this book

This book has special features that will

show you how to get your hands on as

much information as possible! Use the

“become an expert” buttons to find out

more about a subject on other pages.

  !  e  r e  h   s  r  e   w s  n  a  e  h t   d  n i f  s  y   a  w l  a l l  i  w    u o  Y 3

Human body Become
an expert...
Your amazing body
on the skeleton,
The greatest machine you’ll ever own is pages 12-13
your body. It’s more complicated
than any computer, it on digestion,
lasts for a lifetime, and pages 82-83
it’s yours for free.

Body parts

Your body is made up

of hundreds of different Hair

parts. You probably know   s Forehe ad    Inside your body
the names of the bits you Doctors can see
can see, but there are     r  Eyebro  w s   inside your body
many more hidden    a
      E

deep inside you. with special cameras.

    k  s Nose     Ey  e s X-ray cameras take
pictures of hard body
   e
    e
       h
      C 

Li ps    parts like bones. Other
cameras, called scanners,
Te  e   th can see soft body parts.

   H a   n d s    F   i  ngers   

Two of everything

Body parts often come W   
in pairs. You have
r i   s  t    s 

two feet, two eyes,

two ears, two lungs,

and so on. This

means you have

a handy spare in

case one of them

gets damaged. A chest X-ray shows the bones in
your chest. The white shape in the
middle is the heart.

4 What do we call the study of the human body?

Water, water Your amazing body
Water is the most
important chemical Curiosity quiz
in your body. About
two-thirds of your Take a look at the first
few pages in this book
weight is water.
and see if you can
find these pictures.

Robot The ingredients

No substitute Your body is made of just
The human body is too a few simple chemicals,
complicated for robots to plus water.
copy. Robots can copy the
way we walk, but they Carbon is the chemical
can’t think or feel like we do. in diamonds and coal.
A fifth of you is carbon.

Iron makes your blood
red. You have enough to
make one small iron nail.

Phosphorus is in the
tips of matches, as well
as your bones and teeth.

Sodium and chlorine
make salt. Blood is one-
third as salty as sea water.

Potassium is used in
some types of soap. It’s
also in your body fluids.

Nitrogen is important in
muscles. It’s also the main
ingredient in air.

Chimps have Compared to chimps, Being human
hands like ours. our bodies look almost
Although we look different to
hairless.
animals, our bodies are similar

Chimpanzee on the inside. Our closest

animal relatives are

chimpanzees. 5
  .   y     m   o t   a   n    A

Human body

What makes you you?

All human bodies work the same way, but everyone
is different. Nobody looks, sounds, or thinks exactly
like you. You’re different because of the way your
genes and experience shape you as you grow up.

Fair skin

Green eyes

Curly hair

Black hair

Unique

The shape of your face,

the colour of your hair,

and many other things

Freckles make you unique – 
different from

everyone else.
6 How many genes are there in the human body?

What makes you you?

In the genes

Genes are instructions that
build your body and tell it

how to work. Your genes
control many of the things

that make you unique,
like the colour of 
your eyes or how
tall you’ll be.

DNA T he re  ’  s     e n    This girl has a gene that allows  g e t int o  i t    
her to roll up her tongue. The
o     boy doesn’t have the gene, Look in a
so he can’t roll his tongue.
u    

   g     

h     

Your genes  D NA in  si   de      yo   u      mirror and see if you
are stored in can roll your tongue. Don’t
a chemical called to       cheat by squeezing it with
DNA, which looks like a
twisted ladder with four s    your lips. Test your
different types of rung. tr       
The rungs make up a  family to see who
four-letter alphabet that e    
spells out your genes,
like letters in a book. t     has the gene.

ch       to    th  e     S   

u   

n   

DNA can an     d    back  40   0     
split and
copy itself. ti   m      

es   .   

Learning to ride
a bike changes your
brain and your

body.

In the family Changing body
Your genes came from your parents. Genes don’t control
Half come from your mother and everything – experience
half come from your father. If 
you look like your parents, it’s also shapes you.
because you share the same genes. If you exercise a
lot, for instance,
your body gets
stronger.

  .  0  0 0  ,  0 3  t   u o   b  A 7

Human body

Building blocks

Every part of your body is made of 
tiny building blocks called cells, which
fit together like bricks in a wall. Cells
are so small that hundreds could fit
on the point of a pin.

The nucleus DNA is
controls the rest stored in
of the cell. the cell
nucleus.
The inside of 
a cell is packed     D  N   A The skin on your
with a kind of   fingertips is made
living jelly called
cytoplasm. of lots of small
ridges.

Inside a cell

In the middle of a cell
is its control centre – the
nucleus. The nucleus sends
instructions to the rest of 
the cell, telling the cell
what chemicals to make.

Before a cell divides,
the nucleus splits to
make two nuclei.

The outer skin, or Tiny generators
membrane, stops provide cells with
things leaking out. power.

Making new cells The new cells pull apart
A cell makes new cells by dividing. and separate, but they
The two new cells are half the size,
but they soon grow back. Millions of  usually stay close
your cells die every second, but millions neighbours.

of others divide to replace them.

8 How many cells are there in the human body?

How big are cells? Building blocks

Cells are too small to see with the  M o r e t han 200   0  de  a  d    sk   i   n   
naked eye, but scientists can
photograph them through ce    l l  s       
powerful microscopes.
The cells on your skin f e  l    l        
are about a hundredth
of a millimetre wide. o   
ff             
   y    
o    

u   

w   

h    

i         
l         

e     

   y     

o     

u    

r       

  e a     
 d 

  ht    

  si       

  n e s 
  n e t  
   e c

  .

A microscope can The cells on
zoom in to see the the surface of 
tiny, flaky cells on the your skin are tough
ridges of  and flat. They overlap to
a person’s fingerprint.  form layer of armour that
protects the softer cells below.

Fat cells are Many blood cells Nerve cells are thin Bone cells make Cells make tissue
bubble shaped. are red. They carry and wiry. They your bones hard. Your body contains
They store fat oxygen around the carry electrical They live in tiny hundreds of different
under your skin. signals. holes in bones. types of cells that do
body. different jobs. Cells of 
the same type usually
 .   n o i l l  i  r t   0  0 1  t   u o   b  A group together to form
tissue. Fat, muscle,
bone, and nerves are
types of tissue. Blood
is a liquid tissue.

9

Human body Systems

Organizing Organs and
the body tissues work in
teams to carry out
Your cells and tissues are major tasks, like
organized into larger body transporting blood
parts called organs. In turn, or processing food.
your organs work together These teams are
to form body systems. called systems.

Kidney The heart is the largest
organ in
Heart the blood system.
It pumps blood around
Brain the body.

Organs The tubes that carry
blood away from the
An organ is a body part that heart are called
does a specific job. Your heart’s arteries (shown in
 job, for instance is to pump red).
blood. Kidneys clean blood.
The tubes that
carry blood back to
the heart are called
veins (shown in
blue).

Organ transplant Heart and blood
If a vital organ stops working, doctors Your heart, blood, and
may replace it with an organ from another blood vessels make up
the blood system. It
person. This is called a transplant. transports vital supplies
around your body.
10 Which body system makes your
stomach rumble?

Muscles Muscles change Organizing the body
Your muscle system is made the position of your Other systems
of tissues that move parts skeleton by pulling
of your body by pulling different bones. Some of your other
on them or squeezing important systems
them. Your biggest are shown in this list.
muscles all pull
on bones. Breathing system: the
main organs are your
Your fingers lungs, which take in air.
are moved by
muscles in Hormone system: this
your arm.
uses powerful chemicals to
The most powerful control your body and mood.
muscles are
in your legs. Skin, hair, and nails:
these form your body’s
Skeleton protective covering.

Bones and Immune system: this
seeks and destroys germs
 joints make that get into your body.

up the skeletal Urinary system: this
cleans blood and gets
system, an rid of waste chemicals.

inner frame Reproductive system:
these are the organs that
that supports make babies.

the body. Digestive system
Your digestive
A quarter of  organs break
your bones are down food to
provide your
Nerves in your feet. body with energy
and raw materials.
Your nervous system carries
Your mouth is the first
electrical signals around part of the digestive

your body. You need system.

Signals shoot this system to see, A long, twisting tube
along nerves to makes up your
muscles, hear, think, intestines, where
telling them digested food is
when to pull. and react.
absorbed.
Senses, such as Your brain is the
touch, rely on nervous system’s 11
nerve cells that control centre.
send signals to
your brain.   .   m e  t s   y s  e  v i  t  s  e g i  d  e  h  T

1  Skull Smallest bone  S 
2  Jaw bone Around the same length k 
as a grain of rice, this
Skeleton is one of the smallest  e
bones in your body. It  el  
Your bones all join up to   to 
lies deep inside your ear.
make a frame for your body n

called the skeleton. This  a
n
protects your insides, and
 d 
H helps you move about.
 b 
  wo Shoulder  o

n
 e
 s 

m blade A giraffe’s long
   yan neck helps it to
Each finger eat leaves
has three bones, off tall trees.
except for your
  sbri      thumb, which
   aveh  has two.
    you
     g?to   You have eight
small bones in
each wrist.

206 bones There are Rib Neck bones
24 bones in Pelvis Did you know that you
There are 206 bones your spine. have seven bones in your
in an adult skeleton. neck, the same number
Over half of these are found in as a giraffe? The top one
the hands and feet – the parts allows you to move your
of your body that perform the head up and down, the
most complicated movements. second lets you rotate it
from side to side.

       62. T      Your tail bone is Frogs have very short
         tih h      at the very spines to withstand the
  w bottom of your strain of the huge leaps
         born e      spine. they take.
             lepoep
        erar Long lasting t         Thigh bone Snakes are A fish’s
        the Bone is a very hard incredibly bendy spine allows it
     fo material and one of the last h      Shin bone thanks to many to bend its body from
      eon parts to rot away when a identical side to side so it can
    re body is buried. This woman i           vertebrae forming swim smoothly.
lived in the Stone Age, 5000 their long spines.
   g    
h      

b       

o     

n     

 e

  si        

  ht    

 e

 b 

 i   

   g

     se g 

 t   

 a
 n
 d 

 s       

 t r              
 o     

n     
   g     

Skeleton and bones

Head case The frontal bone forms

your forehead.

The most complex part of the d o med p ar  t     o f     

skeleton is the skull. It is  c  r  a  n   i u  m i s t  h e  y  
o u    
made of many bones
r   
that fit together
Helmet s k    u l   l .       
tightly, to protect      T   h   e
the brain and The upper part of the skull

support the face. is like a helmet that protects

the brain. The lower part

forms a structure for your

Eye sockets are facial features to attach to.
made up of seven

different bones.

The brain fills The front of the
most of the nose has no
cranium. bones.

Label

Facial features Teeth are set
This image shows the relationship into the
between your skull and face. There upper and
are no bones shaping the front part lower jaws.
of your nose, your lips, or your ears.

Your nose and ears are

14 shaped by cartilage.

Why does a baby have spaces between its cranial bones?

Head case

The spinal cord     k o f th  e    h  
goes through a
large hole in the    c e    

skull.    a a    

     B d      

Blood vessels
pass through
small holes in the

skull.

There are two Upper jaw The lower
parts to the  jaw is not
upper jaw. shown here.

The lower jaw is Jigsaw Hole in the head
hinged. It is the only
The skull From underneath you can
skull bone that can bones fit clearly see the big hole at the
move. together like the bottom of this skull. The spinal
pieces of a jigsaw. cord – which runs down your
back – meets your brain here.

All but one of the

bones are locked in

place. This makes

the skull very strong.

Face from the past

Scientists can work out what a

Meet the relatives dead person’s face looked like

Chimpanzees and humans share a common ancestor. from their skull alone. They

However, chimps have smaller brains than humans so examine the facial bones and

their craniums are smaller. Chimps also have a large build up artificial cartilage,

ridge above their eyes, and a jutting jaw. muscle, and skin over them. 15

 .   n  r o  b  g  n  i e  b  s  a   w  t i  e l i  h   w    d e   h s  a  u   q s  g  n  i e  b   d  n  a  t s  h t  i  w   d l   u  o c   d   a e  h  s t i   o S

Skeleton and bones

Bendy backbone

Your spine is a length of bones
running down the back of your
body. Without it you couldn’t hold
up your head and body, or make
any sort of movement.

 Y The first seven Stack of bones The thoracic
 o bones are in your vertebrae form
neck. They are Your spine contains 24
 u known as the separate bones called  joints with
cervical vertebrae. vertebrae. At the bottom the ribs.
 r  are nine more vertebrae.
The next 12 They are much smaller A straight
    ps  are called the and are fused together. back is
 n i        thoracic actually quite
vertebrae. curvy.
 e
The five lumbar The fused
  cu           bones of the
vertebrae bear sacrum and
r        coccyx don’t
most of your    a  B allow much
v      movement.
weight.    k c  F   
e      
 o r    
s        o    
f       
    g      n   
s      t    
e     
   p      o     
n      f    
t     i         s
l      
   y     n       e     n  i p  
 , 
e     The spinal cord goes
a     through this hole.
The five sacral
b      vertebrae are
 fused together.
i       
The coccyx Segments of the spine
t       consists of four Each vertebra has a strong, stubby
 fused vertebrae. section that supports the weight of 
k       l            your body, and a hole for the spinal
cord to pass through.
i            
What is a slipped disc?
 e

  ht    

 e
  el      
  e tt    
 r 

“  

 ”s   
 .

16

Shock absorbers Bendy backbone
You twist and bend your spine
almost every time you move. Ribcage
Sandwiched between the vertebrae Your thoracic vertebrae
are pads of cartilage to stop them connect to your ribs.
banging and rubbing against each Together they form a
other and getting worn out. cage around your heart
and lungs. Rib bones
Space for Pad of  are curved. They are
spinal cord cartilage also thinner and more
bendy than the bones
in your spine.

The pads give A woman’s
pelvis is shaped
you a little bit differently to a
man’s. A baby can
Vertebra of movement pass through it
in all
when she
c o  u ld be  directions. gives birth.

   u th  i  s     b   Pelvis
en    d    y  .  .. Reproductive organs and some
    Y   o ... digestive organs rest in the
bowl-shaped hollow of your
pelvis. The sacral vertebrae

and coccyx form

the bottom

The way the of t  h .. w. e bowl.
back curves
means we can’t  t   i       
bend as far
back as we can  h 
 forwards.

a    

Bendy backbone  g   e Btenidnotv oer .  i t       l     

The amount of  Gently feel the o    
movement between bones of your spine t      
each vertebra and its with your fingertips.
o   
neighbours is actually Can you follow
very small, but added f         
together they allow for
   p    

r       

a    

c      

t         

i c               

e      

!      

a large range of  them from neck

movement. to waist?

 .   d  e g  a   m  a  d  s  t  e g  e   a r   b e  t  r e  v  e  h t    n  e  e  w  t e  b  s  d  a  p  e  h t   f o  e   n o    n e  h   w  s ’ t I 17

Skeleton and bones Marrow can be found
in the spine, skull,
Living bone and the main leg and
arm bones.
Their outer surface may be hard
and dry but that doesn’t mean
your bones aren’t alive. Bones
are always growing and
repairing themselves.

What’s inside our bones?

Bone accounts for one
sixth of your body’s
weight. Its clever
structure means
it’s often
lighter than
it looks.

Spongy bone Bone marrow
Parts of some bones have a A jellyish substance
honeycomb structure with lots of  called marrow fills
spaces. This makes them weigh less the centre of many of 
than if they were solid right through. your larger bones. It
supplies your body
Compact bone with red blood cells
The hardest and most at a rate of 3 million
dense part of the bones is cells per second.
the outer layer. It is made
of calcium, a substance
we get from our food. Teeth
are made of calcium too.

18 What are the most commonly broken bones?

Broken bone Living bone
Bones are strong and
flexible enough to cope Curiosity quiz
with a lot of pressure,
Take a look through
but, as this X-ray the skeleton and bones
shows, they sometimes
pages and see if you
break. Luckily they can identify where these
can heal themselves.
bony bits come from.

If the broken bone Become
ends have slipped an expert...
apart they must
be repositioned on the skeleton,
by a doctor before pages 12-13
healing begins.
on skin and nails,
On the mend pages 70-71
New cells form at each end of 
the broken bone, closing the
gap between them. It takes
about 6 weeks for this
to happen.

   s. Padded clothes
help protect
    e n bones from
    e sudden impact.
               l
        t Looking after
                      i l your bones
     e Calcium from
          t  milk and cheese
          t  is needed to build
      s strong bones.
Weight-bearing exercise
     e      a like walking, climbing,
or skating helps to
     r               l strengthen bones.
    a       r
  .  s   m r  a   d  n  a  , s  t s  i  r  w  ,  s  r  e g  n  i F
    n    e  s      u
   g   Yr  o  o  w u    ri  nb   g o  u  n     t     i l
  y  o 

19

Skeleton and bones Baby’s
hand
Bone and cartilage

When you were a baby, you were tiny.
Slowly, as you get older and bigger,
your bones do a clever trick. Not only
do they grow, but they also change.

Making bones More, less

Babies’ bones are made out You’ve got more bones
of a soft and bendy material than your mum or dad!
called cartilage. Slowly this
hardens and turns into bone. You were born with over 300 “soft”
bones, but as you get older, many fuse
Baby bones are entirely
made of soft, growing together. By the time you’re 25 you’ll
cartilage. have 206 fully formed bones.

Adolescent bones are Cross-section of an
mostly bone, with a small ear – the cartilage sits
amount of cartilage. between two layers of 
skin.
Adult bones have
stopped growing. Most no
longer contain cartilage.

Stick out your ears!
Your ears are made of 
cartilage, not bone. They
are strong, but much
more bendy than
your bony bits.

20 Which foods are rich in calcium, the mineral you need to grow healthy bones?

Child’s Bone and cartilage
hand
Adult’s
hand

Bone shows up as purple in
these X-rays. The difference
between the amount of bone
can clearly be seen.

Taller, shorter
Between each bone
in your spine are small
disks of cartilage. During the day
these get squashed, and when you
rest at night they spread out again.
This means you’re a little bit taller
in the morning than in the evening.

Cartilage coats Smooth coated joints
the ends of these The ends of neighbouring
bones are covered in
bones. smooth cartilage. That
way, they can glide against
The pads of  each other when you move.
cartilage get
squashed from
standing up and
stretch back out
while you’re lying
down.

  .  m   a  e  r c  -  e c i   d  n  a   t r   u  g o  y  ,  e  s  e e   h c ,  k l  i   M 21

Skeleton and bones

Moving joints

Joints are the places where
bones meet. Different kinds
of joints allow you to move
in different ways.

Hinge joint Fixed joints
The bones that make up
Your knee can bend your skull start to join up
in the middle but soon after you are born.
it can’t swing from Once they have fused,
side to side. This none of them allow
 joint has a hinge movement except the
like the one that hinged jaw joint.
allows you to
open and Knee joint
close a door.

Have you ever used
a joystick? That’s a ball

and socket joint!

Ball and socket

Your hips are ball and socket joints.
They allow you to move your legs in

There are 19 moveable joints in

all directions and even to turn them. your hand – not counting the ones
in your wrist!

22

What is tennis elbow?

Moving joints

Bendy bits h a nd i s a te  r   r  i  f   i         

Different sorts of joints   Y o  u  r c    
all over your body keep
you moving.  g e t i nt o  i t     f         

Neck bones feature a e a         
pivot joint that allows
your head to turn.  t    

Wrists have a joint that  o
allows them to turn but  f   
not to go right round. Tape your
thumb to your first   n e
Ankles contain different
 joints for up and down  finger. See how      n  i g    
and side to side movement. difficult it is to open a    i r     e  e
notebook, pick up a Thank your thumbs
  n Your thumb is the most
pen, and write
your name.    g flexible of your fingers.
 !   You rely on your thumbs

whenever you handle

Hip hooray delicate objects.

Joints, particularly This woman has
knee and hip joints, stretchy muscles and

sometimes wear out in ligaments that
old age. When this allow her spine
to bend

happens, doctors can  further than
remove the worn-out most people
can manage.

 joint and replace it

with an artificial one.

Ligaments Fabulously
 flexible
Bands of tissue called ligaments act People whose
like elastic. They hold your  joints are
bones together yet particularly
still allow you flexible are
to move. called “double-
 jointed”. The condition
Ligament can run in families, but
people who are double-
Your elbows Bone  jointed must practise if 
have a hinge they want to keep their
 joint for bending ligaments stretchy.
and a pivot joint so
they can turn.

  .  e s   u  r e   v o   y  b    d  e s  u   a c  s   n o  d   n e t    w o  b  l e   e  r  o s   r o f   e  m  a  n  e   h  T 23

Moving muscles

The body’s muscles

Every time you move, you use Pulling strings
muscles. Muscles make you walk,
blink, and smile. Some muscles About 650 of your muscles are
work without you thinking about
them, but others need to be told to wrapped around the bones of 
move. They all work by shrinking,
which makes them pull or squeeze. your skeleton. They move your

body by pulling on the bones.

Together
they form

the muscle

Smooth muscle The pectoralis system.
This type of muscle muscle swings
makes things move your arm.
inside your body. It
mixes food in your The biceps muscle
stomach and pushes bends your arm.

Smooth muscle cells food through
are short your intestines.
with pointed ends.

Heart muscle cells Heart muscle Your longest muscle
are stripy with When you put your is the sartorius. It
oval blobs. hand on your chest, helps cross your
you can feel your legs.
Skeletal muscle cells are heart beating. Your
long and heart is a strong The tibialis muscle
threadlike. muscle that squeezes bends your foot.
blood around your body.
24
Skeletal muscle
Skeletal muscles pull on
bones to change the shape
of your skeleton and
move your body. These
muscles are voluntary,
which means you can use
thought to control them.

What weighs more: all your bones or all your muscles?

The body’s muscles

Muscle magic Who’s in charge?

Muscles have hundreds You use hundreds of muscles when
of uses. They make up
about a third of your you run and jump. Your brain
body weight.
controls them all, a bit like Become
Largest muscle: you use a conductor controlling an an expert ...
the muscle in your buttock orchestra. It sends signals
for sitting and walking. along nerves to every on making sounds,
muscle, saying pages 64-65
Fastest muscle: this one exactly when
makes you blink. It works to work and on how intestines
up to 5 times a second. when to rest. push food,

Ear wiggling: a few pages 88-89
people can control the
muscles around their ears. Hundreds of muscles
work in a carefully
Smile: a fake smile uses controlled sequence
different muscles from a when you jump in the
real, involuntary smile. air.

Tongue twister
Your tongue is a bundle of 
lots of muscles that make it

super flexible. It can reach
anywhere in your mouth
to pull and push bits

of food. Its acrobatic
movements are also
vital to speech.

 n m yl e Y ma    o  s  u  a  t   r k  1  te 4  o    i nd tg iafu f me e ra ce   ozn i  tn  t  ga    l   i  un   ss  f  c  a  l   l  eet    xs       i     tb   h    l  ea   . t   .  s e  l  c s   u  m  r   u  o  Y 25

Moving muscles

How muscles work

Muscles work by contracting, which means
they shorten. As a muscle contracts, it pulls.
The larger the muscle, the more powerfully
it pulls.

When the bicep Working in pairs
muscle contracts, it
pulls your forearm Muscles can pull but
and bends your not push. They work
arm. in pairs that pull in
opposite directions.
When one muscle
pulls, its partner
relaxes.

When the triceps Your forearm
muscle contracts, it contains pairs
straightens your of muscles that
arm. move your hand
and fingers back
and forth.

Fibres in fibres
Skeletal muscles
are made of cells
called muscle fibres.
Inside these are even finer
fibres called myofibrils, which
contract to make a muscle shorten.

A typical
muscle

Bundle of  One muscle cell Myofibrils inside

muscle cells a muscle cell
26 Where is the body’s smallest muscle?

Try raising your Tendons How muscles work
ring finger with
your hand in this Muscles are fastened Making faces
position. to bones by tough bands
It’s stuck because called tendons. When you Muscles in your face are
it’s joined to the wiggle your fingers, you attached to skin as well
same tendon as bone. They pull the
as the middle can see the tendons skin when you change
 finger. move on the back your expression. You
of your hand. use about 17 muscles
when you smile.

Middle finger

Ring finger

A floppy start

A newborn baby has little
control over his head or neck

muscles. It takes about a
month before it can hold up
its head, and six months for
strong, steady head control.

No rest

Muscles work all the time. They hold
you upright - without them you would
flop on the floor. Muscles also work
when you are asleep, keeping your body
firm and toned.

Getting a stitch 27

If you run a lot, you may get a
pain in your side. This is a stitch.
Scientists aren’t sure exactly why
it happens but it might be because
the muscles and ligaments in your
abdomen are working too hard.

  . r   a e  e   h t    n I

Moving muscles Stamina
If you have stamina, you
Muscle power can keep going for a long
time without getting tired.
The more you use your muscles,the Exercise that makes you feel
better they get. Active games and out of breath, like running,
exercise make your muscles larger, improves your stamina.
stronger, and more flexible. They also
help you keep going without tiring.

Flexibility
When you’re flexible,
your joints and muscles can
move freely and your body
can bend and straighten
easily. Exercise that
stretches your body, such
as gymnastics or dancing,
improves your flexibility.

This contortionist has made her body Strength
more flexible by doing exercises that Pushing, pulling, and lifting make
stretch her back. your muscles bigger and stronger.
Bodybuilders lift heavy weights over
and over again until their muscles
are enormous.

n eed s t rong muscles
a tug of -war 
w i n
  Y o u

- . t o

Become
an expert ...

on how your heart
works, pages 50-51

on healthy food,
pages 106-107

28 What happens to muscles if you don’t exercise?

Muscle food Muscle power
Ways to keep fit
To build strong muscles,
you need a type of food Exercise is very good for
called protein. Meat, your health. As well as
fish, beans, milk, and making your muscles
eggs are rich in protein. bigger, it strengthens
your heart and lungs.
Most vegetables
don’t contain much Walking to school, or
protein. going out for walks, builds
strength and stamina.
Body heat Chicken Milk
This picture shows the Fish Egg Football is great for
heat of a man’s body. improving your flexibility
Muscles make heat when Beans and strength.
they work hard, which is
why exercise makes you Fish is a very Swimming strengthens
hot. On cold good source of  your heart muscle and
days, your protein. builds stamina.
muscles try
to warm Cycling strengthens your
you up by leg muscles and builds
shivering. up stamina.

Dancing keeps your
body supple and helps
build strength.

 .  k   a  e  w   d  n  a l l  a    m s   t  e g    y e   h  T 29

Brain and senses Sense signals
The cerebrum is
Headquarters the main part
of your brain.
The brain is the body’s control It gets and stores
centre. It is a complicated organ sense information
that works very quickly,
a bit like a brilliant, and also controls
living computer. your movements.

 C e rebrum

Clever calculator  C e  r e bell u m        em
The cerebrum is
also responsible for        t
thinking, speaking,     s
and complicated
tasks such as sums.   B   r   a     i n

Your brain stem
works at the same
rate whether you’re
awake or asleep.

Muscle control 24 hours a day
Your cerebellum helps you Whatever else you do,
to balance and move your the brain stem makes
muscles. You use this bit of 
your brain when you dance. sure your heart and
breathing never stop.

30 Does your brain hurt when you have a headache?

Headquarters

Skull In relation to the size Curiosity quiz
of our bodies, humans have
Brain the biggest brains of any Take a look through the
brain and senses pages
animal. and see if you can spot

Brain box

Your skull is a bony shell where these come from.

that fits together like a jigsaw

around your brain. Shock-

absorbing liquid fills the space
between the brain and skull.

Learning 31

When you
learn to do
something
you create
connections between
cells in your brain.
Next time you do it the
connections are already
there so it is easier.

Short-term memory
Your short-term memory only
holds information for about a
minute. You use it to compare
prices when you go shopping,
or to remember a name when
you meet someone new.

Long-term memory
Your name, phone numbers
you know by heart, and skills
such as riding a bike can be
kept for many years in your
long-term memory.

 .  n   a c   d   a e  h  r   u o  y   d  n   u  o r  a   s e  l  c s   u  m  e  h t  t  u  b   n i  a  p  l  e e f  t ’  n   a c   n i   a r  b  r   u o  y  ,  o  N

 3   B 

2  r 
 a
Network of nerves i  
n
All of the body contains nerve cells. These
 a
link up to form the network of nerves n
 d 
we call the nervous system. It Brain
 s 
 W transports messages between A good night’s sleep  e
 chhi     the body and the brain. Your body and brain slow down when n
you sleep, but they don’t stop working.  s 
Your brain needs sleep to sort out the  e
events of the previous day.  s 

                      yygodoeestevsetou?birnirnnlh                 Quick as a flash Your knee jumps
 forwards even
Nerve cells lie next to one Cross your though your brain
legs and tap hasn’t
another forming long chains.  just below the told it to move.
knee.
They pass messages to their

neighbours – rather like a Spinal cord –
the centre of 
speedy relay race – to and the network

from the brain. Brain cells viewed
through a
microscope.

No need to think
You do some things without
needing to think about them.
These are called reflex actions
and include blinking, coughing,

and the knee-jerk reflex.

            iensp. Messages  .           in You’ve got 150,000 km Pain-killers
        your (93,200 miles) of nerves When you get a filling,
     fo Your brain      a in your body. the dentist gives you an
         base controls your body. anaesthetic. This drug
        the It receives messages               rt
     to from all parts of  stops nerves passing
       teo your body and        d on pain messages for
        ibg decides what
        yruo to do.       e a short time.
    om       e
Walking is the result of 
your brain telling your      p
leg muscles to move.
        s-
Hunger is your stomach       h
telling your brain that it’s
empty and you must eat.       g

Needing to urinate is              i
a response to the message
that your bladder is full.        h

    a

    n
    a
       h

          t 

      r
      e 
          t
        s

Brain and senses Merkel’s disk responds to
light touch and
Touchy feely
is sensitive to the texture of 
Your skin is in immediate contact with things.
the world. Using your sense of touch
allows you to tell if something is
hot or cold, dull or sharp, rough
or smooth, or wet or dry.

Things we can feel Not worth noticing Meissner’s
Although your brain receives messages all corpuscle senses
Skin is packed with
many sense receptors. the time, it filters out the less important light touch.
Each sort responds to ones. That’s why you’re not constantly
different sensations. aware of the clothes against your skin.

Warmth is detected by .It    f e   e    l s     s l  i m    y   ! .
nerve endings quite close .
to the surface of the skin. .

Cold is felt by different
sensors to heat. Extreme
cold registers as pain.

Deep touch sensors This girl quickly Ouch!
enable you to grip moves her finger
things tightly. The body has
away from the its own system of 
Light touch sensors lie thorn to stop alarm bells. Pain
at the root of hairs on the pain. receptors warn us
your arms and legs. when a part of the
body has been
Vibrations from an hurt or is about
electric drill trigger
vibration sensors. to be harmed.

Tickly feelings result
from a light and
unexpected touch.

Sensitive fingertips full
of receptors are able to
tell coins apart.

34 How many touch receptors are in a fingertip?

Touchy feely

Free nerve endings
respond to heat, cold,
and pain.

Surface of skin The Ruffini ending
Dermis responds to firm or
Fat continuous touch.

Under the skin

Dead cells form the surface
of your skin. Below that lie
sweat glands, hair follicles,
and different types of 
sensory receptors.

The Pacinian corpuscle
responds to firm pressure and
vibration.

....... t he  me ss   age    shoo ts o f f t o t h e b r a i  n.

Sensitive bits Braille was
invented over 150

years ago.

Skin contains more touch

receptors than any other

part of the body. But BIRD
some areas are more

sensitive than others.

Fingertips are packed  g e t i nt o  i t    
with sensors, especially
light pressure receptors. Reading by touch Put one finger
Braille is a system that in cold water, one in hot,
Lips have very thin skin uses raised dots to represent then put both in warm water.
which is good at detecting letters and numbers. It was The water feels cold to the
heat and cold. invented so that people with hot-water finger and hot
bad eyesight would be able to the cold-water finger.
Toes are very sensitive, to read by feeling the page
but thick skin makes the with their fingertips instead

heel less sensitive. of looking at words. 35

 .  y   d o  b  r   u o  y   f o   k  n   u r t  e  h t   f o  e  l o   h  w  e  h t    n o  s  a   e  m   a s  e  h t   y l   h g   u  o r  s ’ t  a  h  T  .  0  0 0  , 3  t   u o   b  A

Brain and senses Different tastes

Taste and smell There are five types of tastes
 – bitter, sour, salty, sweet,
We need to eat and drink to and umami.
survive, but taste and smell
are what make these everyday Bitter foods, such as
activities so enjoyable. coffee can be bad for you.
Most poisons are bitter.
Taste detector
Sour foods include lemon
Your tongue is a big muscle covered and vinegar. Food that
in clusters of taste buds. Each cluster has “gone off” tastes sour.
recognizes a particular kind of taste.
Salt detecting taste buds
can be found on the lips
as well as on the tongue.

Bitter Sweet foods naturally
Sour attract us. Our first food
 – milk – is sweet.

Umami is the savoury
Sour taste of foods like soy

sauce and mushrooms.

Salt     b   u d s a re cramme   d    

Sweet        s  t  e
   a
 g e t i nt o  i t    
       t
Try putting
sugar on different places Salt      0
on your tongue. It tastes       0
sweeter in some places       0
   ,   
than others. Now try
salt, lemon juice,        0 
and coffee.
           1

Taste buds

Saliva in your

mouth dissolves    e .
your food. The food
washes over tiny taste    g   u
buds between the bumps
o n t o y o  u  r t  o   n
on your tongue. Taste buds
recognize different flavours.

36

How much saliva does an average person produce in a day?

Taste and smell

Runny nose Your nose and
When you have a cold, tiny mouth are
hairs in your nose get clogged
with mucus. This stops them linked at the
wafting smell particles deep into throat.
your nose and makes it difficult
to smell – and taste – things.

Sensitive nose

Much of what we
think of as taste is

actually smell.
The back of your

nose is linked to
your mouth so
you can smell
your food as
you chew it.

n o s es can r e  c  o    g   n   i   z     

e   
 ,    S   o  m  e
1    

0     

0     

0      

0      

 d       

   e ffi               

  n e r 

  t 

   m  s

   .   s  l  l     e 

Smell receptors
Special cells deep inside your nose

recognize scent particles floating
in the air. These cells link
directly to your brain.

 .  )  z o l f   3 5  -  5 3 (   s  e r t i l i l l i   m   0  0  5 1  -  0  0  0 1 37

Brain and senses Wandering eyes

Look out! Six muscles control each eye.
You use both eyes when you
Sight is the body’s main sense and look at something, so your
the main way we learn about our eyes move together.
surroundings. Two-thirds of the
information we take in comes Sclera (or white
from our eyes. of the eye)

Iris

Pupil

The middle of the

eyeball is filled

The muscles with fluid.

    A Pupil       . surrounding your

   i    n  t           y  a seommyboejoevboceattmlshl.elmyntatsrk a se c  o   k p     iy r  rm eo  i c suo  i  sv iceisnagn a   a s   f  u i  n   n  g     e  i    qr  p    u    r    e i n  t
     s
    h  g Eyelid       w     n     a
    A
  t        a

   u o   ,          )
      e
 r 
            l
    ye
             i
e      
   m
s      

c                    ( 1    Hidden away
Most of your
o     Sclera   k m eye nestles

u    Iris

l     
d     

d     c a  n d   l  e   . 6 safely in its
socket and is
et    e  c    t      1 protected by pads of 
fat. On the outside,
a  l i  g  h  ted

you can see the iris,

pupil, and some

of the sclera.

38 What is the sleep that collects in our eyes?

Tears are made behind Safekeeping Look out!
each eyelid.
Your eyes are fragile, Eye colour
The iris is the coloured
squidgy balls made of  part of the eye. All eye
colours are produced by
watery jelly so they need one substance, melanin.
Lots of melanin results
Tears drain into tear ducts. to be well protected. in brown eyes, less
These link to your nose, means a lighter shade.
which is why your nose runs Bone in your skull
when you cry. surrounds your brain
and the backs of the eyes.
Crying

Tear glands behind your eyes Eyebrows sit above your
produce drops of salty fluid. eyes and prevent sweat
When you blink, your eyelids dripping into them.
sweep this fluid over your eyes

to keep them clean. If something Eyelids and lashes stop
gets into your eye, or you feel dust entering the eyes and
strong emotions, the drops turn then sweep it well away.

into floods of tears. l    Y  o  u  r p upi s ch  an   ge     si z   e     a u t o ma t ically.

Either it’s dark or this 39
person has seen
something they
like.

Pupil size
The pupil is the
opening that
controls how
much light
enters your
eye. It’s smaller
in bright light to
protect the nerve
cells in your eye,
and bigger in dim
light to let more light
in. It also gets bigger
when you see something
or someone you like.

 .   p  e e  l s   e  w  s  a   s e   y e  r   u o    m  o r f    d e   h s   a  w  s   u c   u  m   d  n  a   t s   u  D

Brain and senses

How we see

Inside your eye is a lens like the lens

of a camera. Its job is to focus light

on the back of your eye so you can

see things clearly.

 f  j  y    r    e   f  l  e  c   t  s o  f a n ob e c t  an  d ente r s y o u  r e  e.

       g   h     t The eye is filled with a

       i
      L semi-solid jelly.

Optic The lens is clear and An object
nerve  flexible. It focuses on
The pupil is a hole
The retina things by changing that lets light into
contains cells shape. the eye.
that sense
light.

How your eye works

Light from an object enters your eye Seeing in colour
through the pupil. It passes through Your eyes contain millions
the lens, and makes an upside down of cells. Cone cells give you
image on the retina at the back of 
your eye. Cells in your eye send colour vision but don’t
messages down the optic nerve work well in dim light.
to your brain. Your brain Rod cells work well
flips the image back the in dim light but
see everything
right way round. in shades
of grey.

40 What is an eye specialist who tests eyesight called?

How we see

Blurry vision   m   b e  r  ? I f not     yo  u     
,
Sometimes an eyeball is the wrong shape.
The lens cannot focus light on the retina and m  
everything is blurry. Glasses make the light
focus in the right place to make things clear.    n   u a   

Short eyeball    y    
If you have a short
eyeball you will have    a b    
difficulty seeing things
close up. This is called     e e     
long sightedness.      e
co           
      s

     u   ol              

      o  u

      y  r 

     n   b 

      a     d   n  i l      
       C

    .

Long eyeball Colour blindness
It is difficult to see
objects that are far away Some people cannot tell certain
when your eyeball is too colours apart, especially red
long. This is known as and green. This is called colour
short sightedness. blindness. It is more common
in men than women.

 g e t int o  i t     Glasses bend
the light entering
Close one eye Contact lenses
and hold a finger in front These work like your eye so it
of your nose. Open that eye mini glasses and  focuses on the
and close the other one. sit directly in
front of the retina.
The finger appears to eye. They’re a
move! Each eye sees bit fiddly, but

things differently.

once they’re in you

can’t feel them at all.

Contact lenses are
made of very thin
plastic.

 .  n  a  i c i t   p o    n  A 41

Brain and senses What can you see?

Eye to brain The dark blue in these
pictures shows how much
Your brain works out what you’re animals can see clearly.
seeing by comparing the images it gets Light blue shows what
from your eyes to things you have seen they can see less well.
in the past. Sometimes it can be fooled!
Humans have to move
c o  m  b i nes image   s  f r  o    m     their heads to see clearly
b   to the sides or look back.
   r  a    i n
b o    Tigers see well to the
    r front to help them find
     o  u th       and catch their prey.

    Y e     Zebras keep a look out for
movements to the sides so
   y     they can avoid attack.

. e    
s     

Ducks can see all the
way behind them, even
while facing forwards.

Chameleons see small
areas clearly. They swivel
their eyes to see all around.

The yellow areas are the parts of 
your brain that deal with
information from your eyes.

Optic nerve

To the brain

Our eyes swivel around constantly,
taking in sights and adjusting to
focus on different things. The
information they collect travels
to the brain through the optic
nerve at the back of the eyes.

Eyeball

Your blind spot is the part of the eye that
can’t see anything. It is where the optic nerve
leaves the back of your eye.

42 What is it called when you look at something and think it’s something else?

Tallest tower Eye to brain
Does the green tower
look taller than the Finding your blind spot
others? That’s because Close your right eye and look
it’s further along the directly at the star. Slowly
track and we expect bring the book to your left eye.
objects further away You reach your blind spot
from us to look smaller. when the circle disappears.
The colours of the towers
also affect the size they
seem to be. In fact, all
the towers are exactly
the same size.

Recognizing objects

Your brain is very clever – it can
recognize this car from different
points of view. A computer would
have to be taught that both these
pictures are of the same object.

Certain
patterns trick your

eyes into seeing
movement where there is

none.

Do you believe your eyes?
Your brain helps your eyes to understand
what they see. Sometimes you see things
that aren’t actually there...

You see a heart 43
even though the
edge of the shape

isn’t there
because your
brain uses the

information
it has to fill

in the gaps.

 .   n o  i s  u l l i l   a c i t   p o    n  A

Brain and senses How well can
you hear?
Listen here
Your hearing range is from
When you shout you send out the highest to the lowest
invisible sound waves through notes that you can hear.
the air. Your ears pick up
the waves and transmit Adults have quite a
the sound to your brain. small range compared
to other animals.
The speed of sound
Children hear higher
We don’t notice the slight notes than adults. Your
delay between someone’s range shrinks with age.

lips moving and Cats, dogs, and rabbits
the sound actually can hear much higher
reaching our ears. notes than people.
It’s too fast!
Bats have excellent
hearing. Their range is
five times as large as ours.

Sound t ra ve l s t h r o  u g  h the 

Headphones feed
different sounds
into each ear so
you feel as if 
you’re surrounded
by instruments.

Why two ears?
Sounds normally reach one ear
first and then the other. This
helps our brains work out
where sounds are coming from
and how far away they are.

44 Why do we have ear wax?

Outer ear Listen here

What we call the ear is A little help
really just the part that Partially deaf 
we can see. Sounds are people may use
hearing aids.
collected here, and These make the
funnelled inwards. sounds entering
the ear louder
and easier to
hear.

Middle ear

Sounds arriving here from the
outer ear cause the eardrum to
vibrate and set off movements
in three tiny little bones.

O     Bones Cochlea

u   Ear canal
t e    r     
e   M         r
a r     
id    d     l e     ea   r    a
.a ir    to    y ou  r  ea r
Ear drum e

  I  n  n  e   r

Inner ear Tiny hairs are
moved by sounds.
The bones moving cause
vibrations in the liquid Signals travel
deep inside the ear. along these nerves
Tiny hairs in your to the brain.
inner ear pick up these
vibrations in the liquid
around them. The hairs
are attached to nerves,
which connect to your brain.

  . s  t  c  e s  n i  l e   p  e r   d  n  a ,  t s  u  d   p   a r t , l  a  n   a c  r   a e  e  h t  g  n i  n i l   n i   k s  e  h t   t  c e  t  o r  p  o  T 45

Brain and senses

Balancing act

As well as hearing, ears

help you balance. Sensors

in your ears work with The three
those in your eyes, semi-circular
muscles, joints, and feet canals deal with

balance.

to let your brain know

your body’s position.   E a r h o l e

Keeping track

Deep inside your ear are three
tiny tubes filled with fluid. They
detect the movements your body
is making and let your brain
know about them.

One tube is for forward and Watch your step!
backward movements, another
 for up and down, and the Keeping your balance
third for side to side while walking along
movements. a narrow wall takes
a lot of concentration.
A jelly-like knob floats in You are responding
each tube. Inside it are to information coming
from your eyes,
sensitive hairs that detect muscles, and ears
movement. at the same time.

46 The movements travel
along the hairs, through
a nerve, to the brain.

Can astronauts learn to balance in space?

 T Motion sickness Balancing act
Travelling in a car,
h        boat, or plane can Muscle messages
make you feel ill. Your When you move, sensors in your
 e       eyes tell your brain muscles send messages to your
that you’re staying brain. If a movement isn’t going
m    still in the vehicle, but right, your brain will make you
your body says it can do things differently.
o      feel movement. This
The brain
r      confusion is what
e     causes motion  g e t i nt o  i t    
sickness.
   y      First make
b  r a  i n is the  b os   s     sure there is nothing
o     unsafe nearby for you
u     . to crash into. Then spin

   p        r round and round
    u and make yourself 
r         y   o
a      feel dizzy.
   y   ,  
c    
t                 l
i                   l
s    
e          a

t             c
h     
            i
e     
       s
b      
     a
e    
      B
t      
Why do you feel dizzy?
t         
The liquid in the tubes of your ear is like water in a cup.
e    When you spin, it continues to slosh around for a while
even after you’ve stopped. Your brain gets confused about
r        which way round you are, and you feel dizzy as a result.

   y        .   w o  h    n r   a e l  o t  s  y  a  d   f o  e l  p   u  o c   a  e  k  a t   n   a c  t i  t  u  b  ,  s e  Y

 o     

 u    

 w   

 i       

 l     l        

 b 

 e

 a

 t    

 b 
 a
  al    
 n
   nic    
     .g

47

4  H
 e
 8   a
r 
 W Blood flow Tube transport  t 
 ehn 
    yuo Blood is the body’s Blood leaves the heart in  a
              yosuuetd,watciknhflr              large blood vessels called n
transport system. arteries, and it returns  d 
Pumped by the heart, in vessels called veins.
it travels around the Between the arteries  b 
body in tubes called and veins are tiny l  
blood vessels, delivering vessels called  o
vital supplies to keep capillaries.  o
 d 
your cells alive.Around the body                    bbeodotsoedoovdoesselfhll                  Blood picks up Lung Lung Artery
oxygen from the Liver Capillary
lungs and carries it Stomach Each major organ
around the rest of  Kidney has an artery
the body. bringing fresh blood
and a vein carrying
Blood travels round away used blood.
your body, passing
The aorta is the biggest Vein
blood vessel in your
      ysuaull      through organs on body. It is as thick as
     oeoc?mrfm     the way. It picks your thumb. A blue
up oxygen in the whale’s aorta is wide
lungs and food in enough to swim through!
the liver, then
gets rid of waste Kidney The vena cava is your
in the kidneys. biggest vein.

 .     y Capillaries

        d Arteries split into
      o  smaller and smaller
branches. Eventually
        b  they turn into capillaries,
which are finer than hairs.
            ru Capillaries lead into veins,
which join together and get
      o bigger on the way back to
the heart.
         m k               y  ni

Become                          0   0 0 ,0                          s    l   es se Artery
an expert... Vein
       0      v
on breathing in         1
and out, pages 60-61       t        d
           ou                    olo
on air and oxygen,
 . pages 62-63         b       b
    ry       a        f
           llia       o
  p            er  Capillaries
    ca      a             ) 
   A        s
      e 
      r       e
      e 
               l
       h               i
      T
    m

       0
       0

       0

Heart and blood Double pump

Boom boom Your heart is really two pumps in
one. One half pumps blood through
Your heart is a pump that your lungs, and the other half pumps
pushes blood around your blood around the rest of your body.
whole body. Each time your
heart beats, it squirts out a Blood from most of  Blood goes out to
small cupful of blood and the body enters the body through the
refills for the next beat. through the vena aorta.
cava.

Where is it? Blood goes
Your heart is in the middle of  out to the
your chest, squeezed between lungs.
the two lungs. You can feel its
beat just left of the bone in  O
the middle of your chest.
 n
 e Blood comes
in from the
 s  lungs

 d  i       

 e

   p

 um       

   p     

 s       

b       

l           

o     
o     

d       

Vena cava t       

o     

t       

h    

e     

lu         
n   

  g   

s    

. 
. 
. 

Aorta

Blood comes Blood goes out

 from the body. to the body.

50 How many times does your heart beat in a year?

One-way system Boom boom

To keep blood flowing one way only, your Curiosity quiz
heart and most veins contain valves. Your
heartbeat is the sound of valves shutting Take a look through the
when your heart squeezes. heart and blood pages
and see if you can spot

any of the cells and
tissues below.

Blood goes out to Valves stop blood
the lungs.  flowing
backwards.

Blood
comes
in from
the lungs.

  . Beating faster
Muscles need extra
    e blood when you’re active,
so your heart speeds up.
          l s It beats about 70 times a
minute if you’re resting
     e but up to 200 times a
minute if you’re running.
     e
      r
     e

       h

   w 

     y

   e       r

     v

      e

        d

      o
      o

          l

       b

      s  g e t i nt o  i t    

     p

    m

        p u  Find your
pulse by pressing two
     r  fingers on your wrist.
     e You should be able to feel
a gentle throb as your
           t h
heart pumps blood
    o around your body.

... a  n d   t h   e

  .  s  e  m  i t    n o i l l  i  m   0 4  t   u o   b  A 51

Heart and blood

All about blood

Blood is a warm, soupy mixture
of liquid and cells. The cells
carry oxygen and fight germs,
and the liquid carries nutrients to
body cells and takes away waste.

Main ingredients
Blood contains three types of cells – 
red blood cells, white blood cells, and
platelets. They float in a yellowish
liquid called plasma.

One drop of  Lots of  White blood
blood contains plasma cells seek

5 million red blood cells, Yellow plasma out and kill
half a million platelet cells, makes up more germs. They
also eat up the
7,000 white blood cells, than half of  dead cells that
water, sugar, salt, your blood.
hormones, vitamins, they meet.
fat, and protein.

  m a  k e blood  re  d    
.

White blood          l   l s

cells and    e

Become platelets.    c

an expert...     d

on fighting germs,     o
    o

           l

        b

pages 78-79         d
on air and oxygen,
      e
pages 62-63
     R

Red blood cells

transport oxygen

 from your lungs to

52 the rest of your body.

How long does a red blood cell live for?