Your body (whats your body made of and how it works?)

Nucleus Chromosome The cells' instructions The nucleus in each cell contains special threads called chromosomes.. The digested food goes into your blood and is carried to every tiny cell

USBORNE HOTSHOTS

YOUR

BODY

USBORNE HOTSHOTS

YOUR

BODY

Written by Susan Meredith

Designed by Fiona Johnson

Illustrated by Kuo Kang Chen,

Colin King and Sue Stitt

Series editor: Judy Tatchell

Series designer: Ruth Russell

Additional illustrations by Chris Lyon,

Guy Smith, Annabel Spenceley

and Peter Wingham

CONTENTS

4 What is your body made of?

6 Where does your food go to?

8 Why do you breathe?

10 What is blood for?

12 Your skin

14 Messages from outside you

18 Inside your head

20 What makes you move?

22 How are babies made?

24 What makes you ill?

26 Looking after your body

29 Amazing facts about your body

32 Index

What is your body made of?

Your body is made of more

than 50 million million

living units called cells

Most cells are so small

that you can only see

them with a powerful

microscope The cells

are about two-thirds

water Food and oxygen

mix together inside them

to give you energy

Different kinds of cells

Cells are different shapes and

sizes depending on the job

they have

to do

This is a group

of skin cells, magnified many times.

One cell This part controls the way the cell works.

It is called the nucleus.

Nerve cell

Nerve cells are very long Messages travel along them

Muscle cell

Nucleus

Muscle cells

are long and

thin They

can shorten

their length

(contract) and

then relax,

which makes

you move

Nucleus Cells lining nose

Cells lining your nose and windpipe have tiny hairs on them These waft germs and dust away from your lungs

Nucleus Chromosome

The cells' instructions

The nucleus in each cell contains special threads called chromosomes These carry the instructions the cell needs to live and work You inherit your chromosomes from your parents Chromosomes are made of a chemical called DNA, which looks a little like a twisted ladder

Growing and repair

Until you are about 18, your body keeps making more and more cells This makes you grow Even when you are grown up, your body continues making some new cells These replace the millions that die every second A new cell is made when an existing cell divides in two

Part of a chromosome The rungs

on the DNA

"ladder" form the coded instructions.

The cell takes in goodness from food and grows.

The nucleus divides and the cell starts to narrow in the middle.

The cell splits in two.

The rungs on the DNA

"ladder" are arranged in a different order in different people This makes the instructions different, and makes everybody unique.

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Where does your food go to?

Without food to use as fuel, your body would soon

stop working Before your body can use it, the food

has to be broken down inside you This process is

called digestion The digested food goes into your

blood and is carried to every tiny cell in your body

Digestion

Digestion takes place as your food

travels through a long tube winding

from your mouth to your bottom

Your teeth bite and chew your food into

small pieces Saliva (spit) moistens it and

makes it easier to swallow Saliva has

a digestive juice in it which starts

breaking up the food When

you swallow the food, it goes

down your oesophagus into

your stomach

Look on the opposite

page to find out what

different parts of the

digestive tube do

Small

intestine

Oesophagus

Stomach

Large intestine

This picture shows

the position of your

digestive system

Rectum Anus

Moving along

Food does not just slide through your digestive tube It is squeezed along

by muscles in the tube

Muscles squeeze here Food is

pushed along.

Food

Stomach

In your stomach the

food is churned up and mixed with stomach juice It becomes rather like soup

Small intestine

Your stomach releases food into your small intestine

Juices finish digesting it The digested food seeps through the thin walls of your small intestine into your blood

Large intestine

Water and any food which cannot be digested move into your large intestine

Most of the water goes into your blood through the walls

of your large intestine

Rectum

Solid waste is stored at the end of your large intestine

in your rectum It is pushed out through your anus when you go to the toilet

Teeth

The hardest substance in your body is the enamel coating on your teeth

There are 32 teeth in a full adult set and 20 in a set of first or "milk" teeth Your teeth are anchored in your jawbone by long roots

Waste water

Any water that your body does not need is turned into urine (pee) in your kidneys These are in your back Urine is stored in your bladder until you go to the toilet

7 6

Blood vessel

Your lungs are in your chest.

The air you breathe is

sucked through your

nose or mouth, down

your windpipe and into the

branching tubes in your lungs

At the ends of the tiniest tubes

are bunches of air sacs These

fill up with air, like balloons

You have about 300 million air

sacs in each lung

The air sac walls are only one

cell thick Oxygen seeps through

them into your blood Your blood

carries it to all your body cells

and brings back carbon dioxide

Why do you breathe?

Before your body can use the energy which is in your

food, the food has to be mixed with oxygen This

is a gas in the air When you breathe in, you

take oxygen into your body

When food and oxygen are combined in

your cells, energy is released At the

same time, a waste gas, called carbon

dioxide, is made You get

rid of this when you

breathe out

Your lungs

from air sac.

Carbon dioxide

seeps out of

blood into air sac.

How you breathe

Your breathing is controlled by muscles between your ribs and by your diaphragm muscle, which is below your lungs

Oxygen goes in.

Ribs move up and out, expanding the space

in your lungs.

Diaphragm moves downward.

Carbon dioxide and water go out.

Ribs move down and in, squeezing air out.

Diaphragm relaxes upward.

Blood vessel

Voice box

The lumpy part at the front of your

Your voice neck is your box is here voice box.

You have some stretchy cords, called vocal cords, in your voice box When you speak, you breathe out and air passes between the cords

It makes them vibrate and produce sounds

Vocal cord

High sounds Low sounds

Muscles in your voice box alter the shape of your vocal cords to produce high or low sounds

8

Air in

and out

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The main job of your blood is to carry food and

oxygen to your cells It also collects up waste for

disposal Your blood is pumped by your heart It flows

around your body in tubes called blood vessels

What is blood for?

Heart and blood vessels

Your heart is about the size of your fist

and is made of muscle It keeps squeezing

so blood spurts out of it into your blood

vessels There are three types of blood

vessels: arteries, capillaries and veins

Arteries are blood vessels which carry blood away from your heart Blood in your arteries is full of

oxygen and is bright red

Capillaries are tiny blood vessels They pass between all the cells of your body Their walls are so thin that substances can pass in and out of them, to and from your cells

Veins are blood vessels which carry blood back to your heart

Blood in your veins is purplish-red

because the oxygen has been used up

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Blood

Blood consists of a mixture of cells floating in a pale yellow liquid called plasma Digested food and waste products are carried in your plasma

White blood cell help to fight off illnesses They Platelets help cuts to surround and stop bleeding They destroy germs.

plug up the wound

by making a clot.

Heartbeat

Your heartbeat is the sound made by two pairs of valves, like gates, in your heart They slam shut after each surge of blood has gone through This stops the blood from flowing back You have valves in your veins,

Red blood cells pick up oxygen as your blood passes through your lungs This turns them bright red.

Circulation

Your blood always goes

in the same direction around your body, as shown here

Pulse

Every time your heart pumps, your arteries throb as blood surges through them You can feel this throbbing, or pulse, at your wrist

Heart

Your skin

Your skin is not just a bag to hold your body together It also

protects you from the outside world It is about 2mm (0.08in)

thick over most of your body and is arranged in two main

layers: the outer epidermis and the inner dermis

Your surface skin is dead This strong protective

covering gradually gets worn away but new cells

from the bottom of the epidermis are

growing up all the time to take its place

Dark or fair? Hair

Your skin produces

a dye called

melanin The more

melanin you have, the darker

your skin

In strong sunlight extra melanin

is produced as protection

against the sun's rays This is

why peoples who originated

in hot, sunny climates

have dark skin

Your hair grows out of pits called follicles Cells at the root of the hair divide and push it upward As your hair

grows, the ends get so far away from your blood that they die

Having a hair cut is painless, because the hair is dead

Hot or cold?

When you are hot, your blood vessels widen so that more blood can flow near the skin's surface and be cooled by the

air This makes you look red

When you are cold, the blood vessels narrow

to prevent heat loss and you look paler

Waterproofing

Your skin is coated with oil made in groups of cells called

sebaceous glands

The oil helps to keep your skin and hair waterproof and supple

Goose pimples

You get goose pimples when you are cold because tiny muscles attached to your hairs contract This makes the hair on your body stand on end This is not much use to humans but in furry animals the hairs trap air This helps to keep the animal warm

Sweat

Sweat is mainly water and salt, which pass into your sweat glands from nearby blood vessels The sweat comes out through holes called pores The air cools you as it

dries the sweat

on your skin

Your eyelashes help

to keep dust and dirt out of your eyes.

Lower eyelid

As this eye looks

at the rocket, the light rays that come from the rocket cross each other behind the lens, so that the picture on the retina is upside down

The brain turns the picture back the right way up

Big or small pupils

When it is dark, your pupils expand to let in as much light

as possible In bright light they shrink to prevent damage to your retina

Tears

Every time you blink, tears wash over your eyes and clean them

Right eye

This part of your eye is called the iris.

Muscles in the iris change the size of your pupils.

Tears are made under your top eyelids.

Tears drain into your nose through the inside corner of your eye.

You can watch your pupils changing size Try looking at them in a mirror, first in a bright place, then in a dim one

If you get something in your eye, extra tears are made to wash it away Nobody knows why people cry when they are upset

Taste

Your tongue has tiny spots called taste buds on it

Receptor cells in the taste buds sense four different tastes:

sweet, sour, salty and bitter Different parts of your tongue pick up the different tastes

Smell

Receptor cells high in your nose are sensitive to smells They sense subtle tastes too This is why you can't taste much if your nose is blocked up

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Messages from outside you

Information from the outside world comes to you through

special nerve cells called receptors When these are stimulated

by light or sound, for example, they produce tiny electrical

impulses, which travel along nerves to your brain Your brain

sorts out what they mean

How you see

Everything you see has rays of light

bouncing off it The light goes into

your eyes through the pupil (the

black dot in the middle) Behind

the pupil is a lens This bends

the light rays so that a clear

picture of what you are

looking at fits onto the back

of your eye (the retina)

Receptor cells which

react to light are in

your retina They

send impulses

your brain

The "whites" of your eyes protect the parts behind.

How you hear

Sound is really vibrations in the air These affect

receptor cells right inside your ears

The outside of your ears is like the big end of a

funnel It collects sounds and directs them down

a tube, called the ear canal

Where the sounds go

The sounds hit a

piece of thin,

tightly-stretched

skin called the ear

drum and make it

vibrate

The vibrations pass Fluid in the cochlea along a chain of

three tiny bones and then to a coiled tube called the cochlea

shakes around and pulls on hairs in the receptor cells These send electrical impulses to the brain

When you move your head,

fluid in the semi-circular canals

swirls around and pulls on

receptor hair cells These send

impulses to your brain, which

tell it about your position

If you spin around and then stop, you may feel dizzy This is because the fluid in the canals continues to swirl for a while, even though your body is still

This confuses your brain

Loud noises

This chart shows the approximate loudness of certain sounds Loudness is measured in decibels (dB)

Repeated exposure to loud noise, say through headphones, can damage the receptors in your ears and make you deaf

Touching and feeling

You have pain receptor cells deep inside you

as well as in your skin.

Pain helps to protect you by warning you when something

is wrong.

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Receptor cells in your skin respond to different sensations such as heat, cold, light touch, pressure, itch or pain You have lots and lots of receptor cells in your mouth, fingers and the soles of your feet

A tiny hurt in one of these places can feel much worse than a hurt in a place with fewer nerve endings

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A mouth ulcer can be very painful because you have so many receptor cells in your mouth.

Balancing

Receptor cells in your skin have different shapes.

Inside your head

Your brain controls your body and makes sure that all the

different parts of you work together It makes sense of what

happens to you and enables you to think, learn and feel Rather

like a computer, your brain receives information, processes it

and decides what action to take

Brain and nerves

Your brain is connected to all

parts of your body by nerves

Messages go to and from

your brain along the

nerves in the form of

electrical impulses,

also called nervous

impulses

3 Brain notices,

"That's an itch!"

2 Message goes along

nerve to brain from

nerve ending

(receptor)

in arm.

Follow the numbered labels to see how a message travels to and from your brain

4 Message goes from brain to hand:

"Scratch itch."

The main pathway for your nerves

is inside your backbone.

Parts of the brain

Different parts of your brain have different jobs to

do There are some parts that nobody knows much about They are probably to

do with thinking, memory and making decisions

Funny bone

You can't normally feel the impulses as they travel along your nerves

However, your funny bone is very close to a nerve and the shooting pain you get when you bang it is an electrical impulse

Sleeping

Dreaming may be a way of making sense

of what has happened

to you

Your brain works even when you are asleep It makes sure your heart keeps beating and that you breathe and digest your food

Two halves of the brain Rapid reflexes

Each half of the brain controls the opposite side of the body This is because the nerves to the two sides of your body cross each other as they leave your brain

The right side of your brain controls the movements of your left hand.

If you prick your finger, you pull your hand away immediately This automatic reaction is called

a reflex It helps to protect you from danger

To do this as fast

as possible, the impulses bypass your brain and go from your spine

to your muscles

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