Download 3 -Humans

8
Humans
What
you will learn
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
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Humans
8a
Organs and Systems
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. Brain
Controls the movement and is the centre of
thinking, memories and emotions. Part of
the nervous system.
1
2. Lungs
Supply the body with oxygen. Part of the
breathing system.
4
3. Kidneys
Keep the blood clean. Part of the excretory
system.
4
5
2
6
3
7
4. Bones
Give support and protection and allow
movement. Part of the skeletal system.
4
5. Heart
Pumps blood round the body. Part of the
circulatory system.
6. Stomach
Stores and mixes food. Part of the
digestive system.
7. Sex organs
Produce sex cells. Part of the reproductive
system.
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Do
you Know?
There are 206 bones in your skeleton.
Posture
How can you take care of your body so that
the systems work well together?
Good Posture is important.
It is wise to take preventive measures before
some thing goes wrong. So we have to be
careful about our body. For example, good
posture when studying and sitting so that
the body is not strained. Incorrect posture
can lead to difficulties with digestion,
muscles or the skeleton.
standing
sitting
These figures show the correct way of
standing, sitting and lifting objects.
lifting objects
?
1
Copy the table below and fill in the gaps.
System
Organs
Function
Skeletal
Bones, muscles
Movement
Respiratory
Circulatory
Digestive
Excretory
Nervous
Reproductive
2
Study the pictures below. Each shows a health
risk that some people will take from time to time.
Copy the title of each picture. Write down the
name of the body system or systems that could
be affected.
K
Ideas
!It is important to keep
the body fit and healthy to
keep the system working
well together.
!Incorrect posture can lead
to difficulties with digestion,
muscles or the skeleton.
Wash your hands
Don’t smoke
Don’t slouch
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Humans
8b
The digestive machine
CUTTING
CHOPPING
ACID
TANK
CRUSHING
MACHINE
FAT
DIGESTER
FOR
CELL
S
THE
TO
Y
O
B D
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 cells
of the body, and any food that is undigested is passed out at the other end.
Into the mouth
Your digestive system starts from your mouth. But even after you have swallowed the
food, it is not really inside your body. The gut or the digestive system is a long tube
about 8-9m long which runs from your mouth to anus.
In your mouth food is broken down into smaller
pieces with the help of teeth and tongue. Your mouth
also produces saliva. This makes your food easier to
be swallowed. It also starts the chemical breakdown
of some of your food.
Down the tube
Once you have swallowed your food, it is moved steadily along
your gut. Muscles squeeze to keep the food moving and to mix it
to a paste. The muscles contract and relax in wave like action
and this is called peristalsis.
Do
peristalsis
you know?
Finely ground food is digested
more quickly than large lumps.
!
Carbohydrates spend the shortest
time in the stomach, fats spend the
largest.
!
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The gut
The chewed food is swallowed and goes into
the oesophagus. This is a muscular tube
which can squeeze food down to the
stomach in 7 seconds.
mouth
Your stomach is a muscular bag containing
acidic juices. It stores food for about 3-4
hours mixing it up and breaking down
protein.
oesophagus
(food tube)
stomach
liver
It takes about 6 hours for food to travel
along the 6m length of your small intestine.
The final breakdown of the food takes place
here.
pancreas
All your undigested food such as fibre
collects in the large intestine. This is passed
out through the anus.
small intestine
large intestine
anus
?
1 Write these sentences in the correct order.
a.
b.
c.
d.
e.
f.
Waste material passes out through the anus.
Food enters the gut through the mouth where
it is chopped into smaller pieces by the teeth.
In the small intestine, digestion is completed
and the digested food is absorbed into the
blood.
After swallowing, food is moved along the gut
by peristalsis.
It enters the stomach, which is a muscular
bag of acidic juices for digesting protein.
In the large intestine, water is removed from
the undigested remains of the food.
K
Ideas
!The digestive system is
a muscular tube running
through the body.
!Food is moved through the
gut by muscles squeezing in
peristalsis.
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Humans
8c
I have a heart
The human heart is made mainly of muscles. It weighs about 375g and is about the size of a
man’s fist. It is a muscle, the most active part in the body but it is not solid muscle. The heart is
hollow inside. The space inside the heart is divided into two by a thick wall of muscle. When the
heart is pumping, the two sides work together. Blood flows into each side, then the heart muscles
contract, squeezing the blood out. It pumps blood to your lungs to pick up oxygen and get rid of
carbon dioxide. It also pumps blood around your body, supplying the needs of all your cells and
carrying away poisonous wastes.
A heart beat pumps it out at high pressure through the arteries.
Your heart beats about 70 times each minute through out your
life.
heart
The heart pumps your blood around a system of tubes called
blood vessels. Some blood vessels carry oxygen rich blood away
from your heart to the body. These are called arteries. Other
blood vessels bring blood loaded with carbon dioxide back to the
heart. These are called veins.
Do
you know?
Your heart beats roughly 160,000
times everyday.
!
In a life time the heart will pump
300 million litres of blood.
!
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Changing Circulation
Your 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.
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120
Your heart
rate(number
of beats in
1 minute)
You step in front of a
car. It hoots at you.
100
Your alarm
goes off
80
60
7am
8am
9am
10am
11am
12noon
1pm
40
sleeping
eating
breakfast
walking to
school
writing
dhivehi
experiment
in science
PE
doing
maths
running
home
Heart Problems
A heart attack occurs when blood vessels to the
heart wall are blocked and the heart muscle is
starved of food and oxygen.
You can look after your heart by:
!
!
!
!
?
Doing regular exercise
Eating a balanced diet, without
too much fat
Controlling your weight
Not smoking
1 What is the job of
a.
b.
heart?
the blood?
2 Arteries and veins do different jobs.
What are they?
3 Answer the questions using the above graph.
a.
b.
c.
What is your normal heart rate (roughly)?
What makes your heart rate go up?
When is your heart rate
i.
ii.
lowest?
highest? Why?
K
Ideas
! The
heart pumps blood
around a system of tubes
called blood vessels.
! The
two main types of
blood vessels are arteries
and veins.
!Arteries carries
oxygenated blood and vein
carry deoxygenated blood.
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Humans
Lung
8d
You breathe air into your lungs and take in oxygen. When you
breathe out, you are getting rid of carbon dioxide and waste. If you
hold your ribs as you breathe in you can feel your lungs filling with
air.
The lungs pass oxygen from the air into the blood supply. Oxygen is
then delivered to all your cells to keep them alive. Healthy lungs are
good at taking oxygen out of the air. Unhealthy lungs are not.
How many times do you breathe in and out each minute?
The Respiratory System
Your lungs are protected inside your rib cage. The lungs are joined to your nose and mouth by
tubes. The lungs and these tubes are known as the respiratory system.
nose
windpipe
(trachea)
mouth
voicebox
(larynx)
You usually breathe air in through your
nose. Inside of your nose is warm, wet and
hairy. The air coming in gets warm and
moist. It is cleaned as dust is trapped in the
hairs. So it is safer to breathe in through
your nose than through your mouth!
bronchi
lungs
Do
ribs
you know?
High up in the mountain the air
has less oxygen.
!
People who live high up have very
big lungs.
!
diaphragm
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Inside the lungs
How do you think that your lungs would be, like
two pink balloons or like a pair of pink sponges?
You need to get as much oxygen out of the air as
possible. Why do you think sponges might be
better for this than balloons?
Air sacs in the lungs
tiny blood
vessel
very thin wall
(only one cell thick)
oxygen goes
into blood
air in
air out
carbon dioxide
comes out of blood
thin layer
of water
Each of your lungs is made up of millions of tiny
air sacs called alveoli. These air sacs make the
lungs look like sponges. The alveoli are
surrounded by several tiny blood vessels. The
alveoli have very thin walls so that the distance
between the air and the blood is very small.
Oxygen goes from the lungs into the blood and
carbon dioxide goes from the blood into the
lungs to be breathed out. This gas exchange takes
place every time you breathe.
Imagine how fast it happens! You never even
notice this exchange taking place.
air sac
What a lot of lung
Gas exchange happens so fast because the alveoli in the lungs
give the lungs a very large surface area. In one lung we have
about 300 million alveoli. If all the alveoli in both the lungs
could be spread out flat, they would cover a tennis court.
?
1 Copy and complete the following sentences.
Use the correct words from below.
air alveoli
surface area
vessels
oxygen
blood
The lungs are made of tiny air sacs called
________. The air sacs have thin moist walls
and a large________. They are close to tiny
blood_______.
K
Ideas
!The lungs are made up of
tiny air sacs called alveoli.
!Gas exchange take place
in the alveoli.
!Alveoli give the lungs a
big surface area so that gas
exchange is faster.
2 Why do people who, live high up have bigger
lungs than the people who live at sea level?
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Humans
8e
Healthy Eating
What would you like for dinner?
Some people eat such a varied diet that it usually includes
everything that is needed to keep the body healthy, without
having 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
Proteins - for growth and
repair
Fats - provides energy and
keep the body warm
Carbohydrates - which gives
energy
But a healthy diet has to include other ingredients as well. Vitamins and minerals are essential for
health. The final ingredient of a healthy diet is roughage (vegetable fibre).
Not more not less
Fat has more energy than carbohydrate. You need some
fat to keep healthy.
If you eat more food than you need for living and
growing, the extra becomes a layer of fat. This acts as
an energy store, but too much fat is very unhealthy.
Too much fat can make you overweight and give you
heart problems.
If you do not eat enough, you get very thin and catch
diseases easily.
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Do
you know?
There is as much protein in
peanuts as in meat. Soya beans
contain more protein than either.
!
There is more water in an apple
than in milk.
!
Balanced Diet
You need all the food substances in the right amounts. When a diet
has 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 food
groups shown below. Malnutrition is caused by having a diet that is
not balanced.
A Regular Habit
The food we can not use should be pushed
out of our bodies as feaces within 24 hours.
If our food does not move through the
body quickly the result is constipation.
So it is important to include foods
which
contain fibre. Fibre provides
bulk during digestion and helps to
prevent constipation. Whole meal
foods, prunes, apricots, peas
and beans are all good sources
of fibre.
food rich in fats
food rich in carbohydrates
food rich in proteins
food rich in vitamins and minerals
K
?
Ideas
!A healthy diet should
1 Fill in the blanks
We must eat the right amount of ______,
______, ______, and __________ for a healthier
diet. If we eat too much we become ________
and give us _______.
2 Explain each of these facts.
a.
b.
Children need more proteins in their diet than
adults.
When people try to lose weight, they need to
cut down the amount of fatty food they eat.
contain foods which contain
carbohydrates, proteins,
fats, vitamins, minerals and
lots of fibre.
!These must be eaten in
the right amounts for a
healthy balanced diet.
!Fibre is important to
include in your diets to
prevent constipation.
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Humans
8f
Why we need vitamins
and minerals
Vitamins and minerals are necessary for life (in fact, vita means life). Humans need only tiny
amounts of each vitamin, but if one of them is missing, a deficiency disease occurs.
Vitamins
As you grow up, your bones get bigger and
longer. You need vitamin D to make sure your
bones and teeth grow strong. If you don’t get
enough vitamin D, your bones are soft and will
not hold your weight without bending. This
condition is called rickets. Cod liver oil is full of
vitamin D and your skin can make vitamin D
using sunlight.
You need vitamin C for
healthy gums and skin. In
the olden days sailors didn’t
get fresh fruit on long
voyages, and many died of
scurvy, the disease caused
by lack of vitamin C.
Vitamin C is found in
oranges and lemons and
lots of green vegetables.
Vitamin A is found in liver, carrot and milk.
You need vitamin
A for good
eyesight. If you do
not take in food
that contains
vitamin A, you get
problems in seeing
at night. You get
night blindness.
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Do
you know?
Most vitamins are now made by
the chemical not extracted from
living things.
!
There are some vitamins which
can do you harm if you eat too much
of them.
!
Minerals
A healthy diet also contains minerals. Small amounts of many different minerals or chemical
elements are essential for life.
We need the mineral, calcium to make our
bones hard and strong. We get lots of
calcium when we drink milk or eat dairy
products.
We need the mineral, iron for our blood to
carry oxygen properly. Without it we feel
tired and weak. We get iron when we eat
red meat, liver, eggs.
The mineral phosphorous is also important for teeth and bones. This is
also important in the cells of our bodies. Phosphorous is present in most
foods we eat.
Iodine is important to keep up the
activity of cells. If there is a lack of
iodine in the food we take, the thyroid
gland in the throat may swell into a
goitre. We get iodine when we eat sea
foods or it is present in iodised table
salt.
Our bodies also need sodium, but many people eat too much
sodium (as sodium chloride or salt) rather than too little. On
average, we use two teaspoonful (10g) of table salt a day. In fact we need only one gram of
salt 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.
?
1 Copy and complete the following sentences.
Use the correct words from below.
calcium
blood
iron
iodine
vitamins
minerals
Human need the right amount of ________ and
_________ to keep the body healthy. We need the
mineral _______ for our body to carry oxygen
properly. Milk is good source of __________ for
healthy bones and teeth.
K
Ideas
!Vitamins and minerals are
essential to keep us healhy.
!They protect our bodies
from various diseases.
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Humans
Fit for life
8g
We often hear people talking about getting fit and keeping
fit. We are encouraged to get fit and stay fit.
But what do we mean by fitness?
“Fitness is having suppleness, strength
and stamina”
Suppleness - Being able to bend, stretch, twist
and turn through a full range of movement.
Strength - Being able to exert force for pushing,
pulling and lifting.
Stamina - Being able to keep going, when
running or walking briskly, without geting tired
and puffed very quickly.
You could even describe fitness as the ability of all
organs of the body to function effectively and efficiently.
Fuelling Fitness
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 skeleton, most of your body gets involved.
Number of heart beats per minute (heart rate)
How exercise affects the heart rate
150
100
after
2 minutes
of hard
exercise
50
at rest
0
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average person
at rest
after
2 minutes
of hard
exercise
Do
you Know?
Two weeks exercise can make a
weak muscle twice as strong.
fit person
Fitness tests
When you exercise your heart beat increases. If you are unfit it increases much
more 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 start
exercising regularly, the heart gets stronger. It beats more strong and efficiently as you
get fit. It can supply all the food and oxygen you need without pumping too hard and
too fast. You will have less chance of getting heart diseases.
More oxygen
When you exercise you need more oxygen, so you breathe more. If you are not very
fit, you soon get puffed because you can not get enough air. But as you practice and
get fitter, your lungs get bigger. You breathe more deeply, and gives you a much
better oxygen supply. You can exercise more without getting so puffed.
?
K
1 When you run to catch up with your friends, what
happens to your
a.
b.
breathing
your heart
2 A fit and an unfit person are sitting reading quietly
together. The fit person’s heart beats more slowly
than the unfit person’s heart. Also, the fit person
breathes fewer times each minute. Why is this?
3 Design a poster to show Do’s and Don’ts for
Ideas
!Fitness is having
suppleness, strength and
stamina and ability of all
organs of the body to
function effectively and
efficently.
!Fitness can be improved
by varied regular exercise.
!Exercise makes your
heart and lungs get stronger.
keeping fit.
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Humans
8h
Smoking can kill you
Tobacco smoke contains chemicals that can damage your lungs.
Tar is a dark brown, sticky substance, which collects in
the lungs as the tobacco smoke cools. It goes into the
alveoli. As tar builds up, the alveoli are damaged. The
thin walls of alveoli get so thicker that it becomes difficult
to exchange gases properly. It also contains substances
which cause cancer. Lung cancer is a very dangerous
type of cancer. It can grow without causing problems
until it is too late to cure.
Nicotine is a poison. It makes the arteries narrower.
Then your heart has to pump harder to push blood
along.
Smokers also get coughs, shortness of breath and
lots of phlegm. Not only it damage the lungs,
smoking is very bad for the heart too.
Do
you know?
Cigarrette smoke in the air
contains higher concentrations of
harmful chemicals about twice as
much nicotine, three times more tar
and five times more carbon dioxide.
!
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Damage the cleaning system
Inside the tubes of your respiratory system has
hair like structures called cilia. The whip like
movements of these cilia move dirt and mucus
out of the tubes, keeping your lungs pink and
clean. But tobacco smoke stops the cilia working.
Tar and also other mucus get into the lungs. It
really is no wonder smokers cough.
Passive smoking
You can damage your lungs by breathing in smoke from
other people’s cigarettes. This is called passive smoking.
So you have to be away from smoky places to prevent the
damage.
K
Ideas
!Cigarrette smoke
?
contains tar which can
cause lung cancer.
1 Why does smoking make gas exchange in the
lungs more difficult.
2 Write a paragrapgh to explain why smoking is not
a good idea.
3 Make a poster to warn people how dangerous
!It also makes the alveoli
thick and exchanges of
gases become difficult.
!It increases the risk of
many diseases.
smoking can be.
87
Humans
8i
keeping clean
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.
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 skin
and teeth healthy.
The skin is the largest organ of the human body. It covers a person
completely from head to toe. Skin is water proof and tough
enough to protect someone from germs and dirt. Skin contains
nerves which send messages to the brain about the texture or
surface of things that we touch. The skin gives you identity by
defining the colour and shape a person sees in a mirror.
Do
you Know?
Skin cells keep dividing and making
new cells through the year.
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Skin care
When you are a teenager you may sweat more
and your skin may become very greasy. This is
normal part of development and there is
nothing wrong with you. But you do need to
be more careful about washing your face,
hands and body to remove the dirt and grease.
If you didn’t the sebaceous glands and the
sweat glands and pores can get blocked and
they become infected by germs.
How does the soap help to keep you clean?
Grease can not dissolve in water but it can dissolve
in the chemicals that make soap. The soap can also
mix with water. So when you wash, the soap and
water remove the grease, dirt and the germs that are
mixed in with them.
K
Ideas
!The sebaceous glands,
sweat glands and pores can
get blocked if you are not
careful about washing.
?
!Soap and water is used
1 Make a poster to show that good hygiene is
to remove the grease, dirt
and germs.
necessary to look attractive and be healthy.
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Humans
8j
Teeth for lifetime
Some people crack nuts with their teeth and even use them to
wrench the tops of bottles. Acrobats can even hang by their teeth.
You are not recommended to do any of these if you want your
teeth to last a life time. But this gives you some idea of how strong
your teeth are.
Tooth Decay
Tooth decay starts when harmful bacteria in
your mouth form a sticky film that covers the
teeth. This film is called plaque. Sugar in your
food mixes with the plaque to make an acid.
The acid starts to eat into the enamel that
covers the outside of the tooth and so the
tooth starts to decay.
Do
you know?
The enamel that covers the
outside of teeth is the hardest
substance in the body, but it is
affected by acid.
!
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Tooth care
The first and most effective step is to brush your teeth
regularly, last thing at night and after every meal. This
reduces the plaque and so prevents the formation of the
acids which causes teeth decay.
The dangers of a sweet tooth
The more sugar and
sugary foods you eat,
greater is the risk of
tooth decay. If you
cannot brush your teeth
easily after a meal, eat a
piece of cheese. Cheese
neutralises the acid
formed.
cheese
K
Ideas
!Plaque mix with sugar to
make an acid. This acid
eats away the enamel.
?
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 your
!Most effective way to
prevent tooth decay is to
brush teeth regularly and
reduce the sugary food we
eat.
teeth.
91
Humans
MOHAMMAD IBN ZAKARIY
A AL-RAZI
AKARIYA
(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 learnt
medicine, mathematics, astronomy, chemistry and philosophy.
In medicine, his contribution was so significant that it can only be
compared to that of Ibn Sina. His al-Judari wal Hasabah was the
first treatise on smallpox and chicken-pox, and is largely based on
Razi’s original contribution. He became the first to draw clear
comparisons between smallpox and chicken-pox. Al-Hawi was the
largest medical encyclopaedia composed by then. It contained on
each medical subject all important information that was available
from Greek and Arab sources, and this was concluded by him by
giving his own remarks based on his experience and views. A special
feature of his medical system was that he greatly favoured cure
through correct and regulated food. This was combined with his
emphasis on the influence of psychological factors on health. He
also tried proposed remedies first on animals in order to evaluate in
their effects and side effects. He was also an expert surgeon and was
the first to use opium for anaesthesia.
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