71

Humans

Organs and Systems

The digestive system

I have a heart

Lung

Healthy eating

Why we need vitamin and minerals

Fit for life

Smoking can kill you

Keeping clean

Teeth for life time

you will learnWhat

8

72

Humans

Organs and Systems8a

Do you Know?There are 206 bones in your skeleton.

The human body is made up of millions of cells. Groups of similar cells form tissues.

An organ is formed from several different types of tissues. It carries out one particular job.When you are fit and healthy all the organ systems of your body work well together.

1. BrainControls the movement and is the centre ofthinking, memories and emotions. Part ofthe nervous system.

Supply the body with oxygen. Part of thebreathing system.

2. Lungs

3. KidneysKeep the blood clean. Part of the excretorysystem.

4. BonesGive support and protection and allowmovement. Part of the skeletal system.

5. HeartPumps blood round the body. Part of thecirculatory system.

6. StomachStores and mixes food. Part of thedigestive system.

Produce sex cells. Part of the reproductivesystem.

7. Sex organs

2

3

1

44

5

6

7

4

73

PostureHow can you take care of your body so thatthe systems work well together?Good Posture is important.It is wise to take preventive measures beforesome thing goes wrong. So we have to becareful about our body. For example, goodposture when studying and sitting so thatthe body is not strained. Incorrect posturecan lead to difficulties with digestion,muscles or the skeleton.

These figures show the correct way ofstanding, sitting and lifting objects.

IdeasK!It is important to keepthe body fit and healthy tokeep the system workingwell together.

!Incorrect posture can leadto difficulties with digestion,muscles or the skeleton.

System Organs Function

SkeletalRespiratoryCirculatoryDigestiveExcretoryNervousReproductive

Bones, muscles Movement

2 Study the pictures below. Each shows a healthrisk that some people will take from time to time.Copy the title of each picture. Write down thename of the body system or systems that couldbe affected.

standing

sitting

lifting objects

Don’t slouch

? 1 Copy the table below and fill in the gaps.

Don’t smokeWash your hands

74

Humans

The digestive machine

Our digestive system is like a factory conveyor belt. Food travels, along the gut,getting broken down at various points. Small useful molecules are sent to the cellsof the body, and any food that is undigested is passed out at the other end.

Your digestive system starts from your mouth. But even after you have swallowed thefood, it is not really inside your body. The gut or the digestive system is a long tubeabout 8-9m long which runs from your mouth to anus.

In your mouth food is broken down into smallerpieces with the help of teeth and tongue. Your mouthalso produces saliva. This makes your food easier tobe swallowed. It also starts the chemical breakdownof some of your food.

Do you know?! Finely ground food is digestedmore quickly than large lumps.

! Carbohydrates spend the shortesttime in the stomach, fats spend thelargest.

8b

Down the tube

Into the mouth

FORCELLS TO THE

BODY

ACIDTANK

CRUSHINGMACHINE

FATDIGESTER

CUTTING

CHOPPING

Once you have swallowed your food, it is moved steadily alongyour gut. Muscles squeeze to keep the food moving and to mix itto a paste. The muscles contract and relax in wave like actionand this is called peristalsis.

peristalsis

75

The gutThe chewed food is swallowed and goes intothe oesophagus. This is a muscular tubewhich can squeeze food down to thestomach in 7 seconds.

Your stomach is a muscular bag containingacidic juices. It stores food for about 3-4hours mixing it up and breaking downprotein.

It takes about 6 hours for food to travelalong the 6m length of your small intestine.The final breakdown of the food takes placehere.

All your undigested food such as fibrecollects in the large intestine. This is passedout through the anus.

IdeasK!The digestive system isa muscular tube runningthrough the body.

!Food is moved through thegut by muscles squeezing inperistalsis.

1 Write these sentences in the correct order.a. Waste material passes out through the anus.b. Food enters the gut through the mouth where

it is chopped into smaller pieces by the teeth.c. In the small intestine, digestion is completed

and the digested food is absorbed into theblood.

d. After swallowing, food is moved along the gutby peristalsis.

e. It enters the stomach, which is a muscularbag of acidic juices for digesting protein.

f. In the large intestine, water is removed fromthe undigested remains of the food.

?

mouth

oesophagus(food tube)

liver

stomach

pancreas

small intestine

large intestine

anus

76

Humans

I have a heart

A heart beat pumps it out at high pressure through the arteries.Your heart beats about 70 times each minute through out yourlife.

The heart pumps your blood around a system of tubes calledblood vessels. Some blood vessels carry oxygen rich blood awayfrom your heart to the body. These are called arteries. Otherblood vessels bring blood loaded with carbon dioxide back to theheart. These are called veins.

Do you know?! Your heart beats roughly 160,000times everyday.

! In a life time the heart will pump300 million litres of blood.

8c

The human heart is made mainly of muscles. It weighs about 375g and is about the size of aman’s fist. It is a muscle, the most active part in the body but it is not solid muscle. The heart ishollow inside. The space inside the heart is divided into two by a thick wall of muscle. When theheart is pumping, the two sides work together. Blood flows into each side, then the heart musclescontract, squeezing the blood out. It pumps blood to your lungs to pick up oxygen and get rid ofcarbon dioxide. It also pumps blood around your body, supplying the needs of all your cells andcarrying away poisonous wastes.

heart

77

?

Changing CirculationYour heart does not always beat at the same rate.Your heart rate depends on what you are doing, and change many times a day.This graph shows the kind of changes which could well take place in it.

IdeasK!The heart pumps bloodaround a system of tubescalled blood vessels.

!The two main types ofblood vessels are arteriesand veins.

!Arteries carriesoxygenated blood and veincarry deoxygenated blood.

2 Arteries and veins do different jobs. What are they?

3 Answer the questions using the above graph.

a. What is your normal heart rate (roughly)?b. What makes your heart rate go up?c. When is your heart rate

i. lowest?ii. highest? Why?

40

80

120

60

100

140

7am 8am 9am 10am 11am 12noon 1pm

Your heartrate(numberof beats in1 minute)

sleeping eatingbreakfast

walking toschool

writingdhivehi

experimentin science

PE doingmaths

runninghome

Your alarmgoes off

You step in front of acar. It hoots at you.

Heart ProblemsA heart attack occurs when blood vessels to theheart wall are blocked and the heart muscle isstarved of food and oxygen.

! Doing regular exercise! Eating a balanced diet, without

too much fat! Controlling your weight! Not smoking

You can look after your heart by:

1 What is the job ofa. heart?b. the blood?

78

Humans

Lung

You breathe air into your lungs and take in oxygen. When youbreathe out, you are getting rid of carbon dioxide and waste. If youhold your ribs as you breathe in you can feel your lungs filling withair.

The lungs pass oxygen from the air into the blood supply. Oxygen isthen delivered to all your cells to keep them alive. Healthy lungs aregood at taking oxygen out of the air. Unhealthy lungs are not.How many times do you breathe in and out each minute?

Your lungs are protected inside your rib cage. The lungs are joined to your nose and mouth bytubes. The lungs and these tubes are known as the respiratory system.

You usually breathe air in through yournose. Inside of your nose is warm, wet andhairy. The air coming in gets warm andmoist. It is cleaned as dust is trapped in thehairs. So it is safer to breathe in throughyour nose than through your mouth!

Do you know?! High up in the mountain the airhas less oxygen.

! People who live high up have verybig lungs.

8d

The Respiratory System

bronchi

lungs

ribs

voicebox(larynx)

diaphragm

windpipe(trachea)

mouth

nose

79

Inside the lungsHow do you think that your lungs would be, liketwo pink balloons or like a pair of pink sponges?

You need to get as much oxygen out of the air aspossible. Why do you think sponges might bebetter for this than balloons?

IdeasK!The lungs are made up oftiny air sacs called alveoli.

!Gas exchange take placein the alveoli.

!Alveoli give the lungs abig surface area so that gasexchange is faster.

?

2 Why do people who, live high up have biggerlungs than the people who live at sea level?

1 Copy and complete the following sentences.Use the correct words from below.

The lungs are made of tiny air sacs called________. The air sacs have thin moist wallsand a large________. They are close to tinyblood_______.

air alveoli vessels oxygen bloodsurface area

Gas exchange happens so fast because the alveoli in the lungsgive the lungs a very large surface area. In one lung we haveabout 300 million alveoli. If all the alveoli in both the lungscould be spread out flat, they would cover a tennis court.

What a lot of lung

Each of your lungs is made up of millions of tinyair sacs called alveoli. These air sacs make thelungs look like sponges. The alveoli aresurrounded by several tiny blood vessels. Thealveoli have very thin walls so that the distancebetween the air and the blood is very small.Oxygen goes from the lungs into the blood andcarbon dioxide goes from the blood into thelungs to be breathed out. This gas exchange takesplace every time you breathe.

Imagine how fast it happens! You never evennotice this exchange taking place.

Air sacs in the lungs

tiny bloodvessel

very thin wall(only one cell thick)

air outair in

carbon dioxidecomes out of blood

oxygen goesinto blood

thin layerof water

air sac

80

Humans

Healthy Eating

What would you like for dinner?

Some people eat such a varied diet that it usually includeseverything that is needed to keep the body healthy, withouthaving them to think about it.

Why do you need food and what food do you need?

The food you eat supplies the raw materials for building the body and for making it work properly.These raw materials are

Do you know?! There is as much protein inpeanuts as in meat. Soya beanscontain more protein than either.

! There is more water in an applethan in milk.

8e

But a healthy diet has to include other ingredients as well. Vitamins and minerals are essential forhealth. The final ingredient of a healthy diet is roughage (vegetable fibre).

Fat has more energy than carbohydrate. You need somefat to keep healthy.

If you eat more food than you need for living andgrowing, the extra becomes a layer of fat. This acts asan energy store, but too much fat is very unhealthy.Too much fat can make you overweight and give youheart problems.

If you do not eat enough, you get very thin and catchdiseases easily.

Not more not less

Fats - provides energy andkeep the body warm

Proteins - for growth andrepair

Carbohydrates - which givesenergy

81

?

Balanced DietYou need all the food substances in the right amounts. When a diethas the right things in the right amounts, it is called a balanced diet.

A simple rule is to eat something everyday from each of the four foodgroups shown below. Malnutrition is caused by having a diet that isnot balanced.

IdeasK!A healthy diet shouldcontain foods which containcarbohydrates, proteins,fats, vitamins, minerals andlots of fibre.

!These must be eaten inthe right amounts for ahealthy balanced diet.

!Fibre is important toinclude in your diets toprevent constipation.

2 Explain each of these facts.a. Children need more proteins in their diet than

adults.b. When people try to lose weight, they need to

cut down the amount of fatty food they eat.

1 Fill in the blanksWe must eat the right amount of ______,______, ______, and __________ for a healthierdiet. If we eat too much we become ________and give us _______.

A Regular HabitThe food we can not use should be pushedout of our bodies as feaces within 24 hours.If our food does not move through thebody quickly the result is constipation.So it is important to include foodswhich contain fibre. Fibre providesbulk during digestion and helps toprevent constipation. Whole mealfoods, prunes, apricots, peasand beans are all good sourcesof fibre.

food rich in carbohydrates food rich in vitamins and minerals

food rich in proteins

food rich in fats

82

Humans

Why we need vitaminsand minerals

Vitamins and minerals are necessary for life (in fact, vita means life). Humans need only tinyamounts of each vitamin, but if one of them is missing, a deficiency disease occurs.

As you grow up, your bones get bigger andlonger. You need vitamin D to make sure yourbones and teeth grow strong. If you don’t getenough vitamin D, your bones are soft and willnot hold your weight without bending. Thiscondition is called rickets. Cod liver oil is full ofvitamin D and your skin can make vitamin Dusing sunlight.

You need vitamin C forhealthy gums and skin. Inthe olden days sailors didn’tget fresh fruit on longvoyages, and many died ofscurvy, the disease causedby lack of vitamin C.Vitamin C is found inoranges and lemons andlots of green vegetables.

Vitamin A is found in liver, carrot and milk.You need vitaminA for goodeyesight. If you donot take in foodthat containsvitamin A, you getproblems in seeingat night. You getnight blindness.

Do you know?! Most vitamins are now made bythe chemical not extracted fromliving things.

! There are some vitamins whichcan do you harm if you eat too muchof them.

8f

Vitamins

83

MineralsA healthy diet also contains minerals. Small amounts of many different minerals or chemicalelements are essential for life.

We need the mineral, calcium to make ourbones hard and strong. We get lots ofcalcium when we drink milk or eat dairyproducts.

We need the mineral, iron for our blood tocarry oxygen properly. Without it we feeltired and weak. We get iron when we eatred meat, liver, eggs.

The mineral phosphorous is also important for teeth and bones. This isalso important in the cells of our bodies. Phosphorous is present in mostfoods we eat.

Iodine is important to keep up theactivity of cells. If there is a lack ofiodine in the food we take, the thyroidgland in the throat may swell into agoitre. We get iodine when we eat seafoods or it is present in iodised tablesalt.

Our bodies also need sodium, but many people eat too muchsodium (as sodium chloride or salt) rather than too little. Onaverage, we use two teaspoonful (10g) of table salt a day. In fact we need only one gram ofsalt each day, not the 10g most of us eat. Too much salt can lead to high blood pressure.People with high blood pressure are likely to have heart diseases and strokes.

IdeasK!Vitamins and minerals areessential to keep us healhy.

!They protect our bodiesfrom various diseases.

? 1 Copy and complete the following sentences.Use the correct words from below.

Human need the right amount of ________ and_________ to keep the body healthy. We need themineral _______ for our body to carry oxygenproperly. Milk is good source of __________ forhealthy bones and teeth.

calcium blood vitamins mineralsiron iodine

84

Humans

Fit for life

Suppleness - Being able to bend, stretch, twistand turn through a full range of movement.Strength - Being able to exert force for pushing,pulling and lifting.Stamina - Being able to keep going, whenrunning or walking briskly, without geting tiredand puffed very quickly.

You could even describe fitness as the ability of allorgans of the body to function effectively and efficiently.

You can improve the three kinds of fitness mentioned above by making sure you have varied,regular exercise. When you exercise, it is not only about the muscles and moving your skel-eton, most of your body gets involved.

We often hear people talking about getting fit and keepingfit. We are encouraged to get fit and stay fit.

Do you Know?Two weeks exercise can make aweak muscle twice as strong.

8g

Fuelling Fitness

Num

ber

of h

eart

bea

ts p

er m

inut

e (h

eart

rat

e)

at rest

after2 minutes

of hardexercise

at rest

after2 minutes

of hardexercise

0

50

100

150

average person fit person

How exercise affects the heart rate

But what do we mean by fitness?“Fitness is having suppleness, strengthand stamina”

85

?

Fitness testsWhen you exercise your heart beat increases. If you are unfit it increases muchmore than if you are fit. It will also return to normal more slowly if you are unfit.

When you first start exercising your heart pounds with the effort, but when you startexercising regularly, the heart gets stronger. It beats more strong and efficiently as youget fit. It can supply all the food and oxygen you need without pumping too hard andtoo fast. You will have less chance of getting heart diseases.

IdeasK!Fitness is havingsuppleness, strength andstamina and ability of allorgans of the body tofunction effectively andefficently.

!Fitness can be improvedby varied regular exercise.

!Exercise makes yourheart and lungs get stronger.

2 A fit and an unfit person are sitting reading quietlytogether. The fit person’s heart beats more slowlythan the unfit person’s heart. Also, the fit personbreathes fewer times each minute. Why is this?

3 Design a poster to show Do’s and Don’ts forkeeping fit.

1 When you run to catch up with your friends, whathappens to your

a. breathingb. your heart

More oxygenWhen you exercise you need more oxygen, so you breathe more. If you are not veryfit, you soon get puffed because you can not get enough air. But as you practice andget fitter, your lungs get bigger. You breathe more deeply, and gives you a muchbetter oxygen supply. You can exercise more without getting so puffed.

86

Humans

Smoking can kill you

Tobacco smoke contains chemicals that can damage your lungs.

Smokers also get coughs, shortness of breath andlots of phlegm. Not only it damage the lungs,smoking is very bad for the heart too.

Do you know?! Cigarrette smoke in the aircontains higher concentrations ofharmful chemicals about twice asmuch nicotine, three times more tarand five times more carbon dioxide.

8h

Tar is a dark brown, sticky substance, which collects inthe lungs as the tobacco smoke cools. It goes into thealveoli. As tar builds up, the alveoli are damaged. Thethin walls of alveoli get so thicker that it becomes difficultto exchange gases properly. It also contains substanceswhich cause cancer. Lung cancer is a very dangeroustype of cancer. It can grow without causing problemsuntil it is too late to cure.

Nicotine is a poison. It makes the arteries narrower.Then your heart has to pump harder to push bloodalong.

87

Damage the cleaning systemInside the tubes of your respiratory system hashair like structures called cilia. The whip likemovements of these cilia move dirt and mucusout of the tubes, keeping your lungs pink andclean. But tobacco smoke stops the cilia working.Tar and also other mucus get into the lungs. Itreally is no wonder smokers cough.

You can damage your lungs by breathing in smoke fromother people’s cigarettes. This is called passive smoking.So you have to be away from smoky places to prevent thedamage.

IdeasK!Cigarrette smokecontains tar which cancause lung cancer.

!It also makes the alveolithick and exchanges ofgases become difficult.

!It increases the risk ofmany diseases.

1 Why does smoking make gas exchange in thelungs more difficult.

2 Write a paragrapgh to explain why smoking is nota good idea.

3 Make a poster to warn people how dangeroussmoking can be.

?

Passive smoking

88

Humans

8i keeping clean

What happened to make the two faces so different?Could it be anything to do with hygiene?Write down two things that you should do to keep your skinand teeth healthy.

Negletting your body is not only unattractive, its unhealthy too!

Look at the pictures of the boys. Now write down two things that are different about them.

The skin is the largest organ of the human body. It covers a personcompletely from head to toe. Skin is water proof and toughenough to protect someone from germs and dirt. Skin containsnerves which send messages to the brain about the texture orsurface of things that we touch. The skin gives you identity bydefining the colour and shape a person sees in a mirror.

Do you Know?Skin cells keep dividing and makingnew cells through the year.

89

1 Make a poster to show that good hygiene isnecessary to look attractive and be healthy.

?

Skin careWhen you are a teenager you may sweat moreand your skin may become very greasy. This isnormal part of development and there isnothing wrong with you. But you do need tobe more careful about washing your face,hands and body to remove the dirt and grease.If you didn’t the sebaceous glands and thesweat glands and pores can get blocked andthey become infected by germs.

Grease can not dissolve in water but it can dissolvein the chemicals that make soap. The soap can alsomix with water. So when you wash, the soap andwater remove the grease, dirt and the germs that aremixed in with them.

How does the soap help to keep you clean?

IdeasK!The sebaceous glands,sweat glands and pores canget blocked if you are notcareful about washing.

!Soap and water is usedto remove the grease, dirtand germs.

90

Humans

Teeth for lifetime

Some people crack nuts with their teeth and even use them towrench the tops of bottles. Acrobats can even hang by their teeth.You are not recommended to do any of these if you want yourteeth to last a life time. But this gives you some idea of how strongyour teeth are.

Tooth DecayTooth decay starts when harmful bacteria inyour mouth form a sticky film that covers theteeth. This film is called plaque. Sugar in yourfood mixes with the plaque to make an acid.The acid starts to eat into the enamel thatcovers the outside of the tooth and so thetooth starts to decay.

Do you know?! The enamel that covers theoutside of teeth is the hardestsubstance in the body, but it isaffected by acid.

8j

91

Tooth careThe first and most effective step is to brush your teethregularly, last thing at night and after every meal. Thisreduces the plaque and so prevents the formation of theacids which causes teeth decay.

The dangers of a sweet tooth

The more sugar andsugary foods you eat,greater is the risk oftooth decay. If youcannot brush your teetheasily after a meal, eat apiece of cheese. Cheeseneutralises the acidformed.

1 What is a plaque, and how does it form?

2 Why does plaque cause problems for your teeth?

3 Make a poster with some rules to care for yourteeth.

?

cheese

K!Plaque mix with sugar tomake an acid. This acideats away the enamel.

!Most effective way toprevent tooth decay is tobrush teeth regularly andreduce the sugary food weeat.

Ideas

92

Humans

MMMMMOHAMMADOHAMMADOHAMMADOHAMMADOHAMMAD I I I I IBNBNBNBNBN Z Z Z Z ZAKARIYAKARIYAKARIYAKARIYAKARIYAAAAA A A A A ALLLLL-R-R-R-R-RAZIAZIAZIAZIAZI(864-930C.E.)(864-930C.E.)(864-930C.E.)(864-930C.E.)(864-930C.E.)

Abu Bakr Mohammad Ibn Zakariya al-Razi was born at Ray,Iran. Initially, he was interested in music but later on he learntmedicine, mathematics, astronomy, chemistry and philosophy.

In medicine, his contribution was so significant that it can only becompared to that of Ibn Sina. His al-Judari wal Hasabah was thefirst treatise on smallpox and chicken-pox, and is largely based onRazi’s original contribution. He became the first to draw clearcomparisons between smallpox and chicken-pox. Al-Hawi was thelargest medical encyclopaedia composed by then. It contained oneach medical subject all important information that was availablefrom Greek and Arab sources, and this was concluded by him bygiving his own remarks based on his experience and views. A specialfeature of his medical system was that he greatly favoured curethrough correct and regulated food. This was combined with hisemphasis on the influence of psychological factors on health. Healso tried proposed remedies first on animals in order to evaluate intheir effects and side effects. He was also an expert surgeon and wasthe first to use opium for anaesthesia.