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P5/6 science

The Respiratory System

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Taken from ScieNce PartNer: a complete Guide to Upper Block Science

Respiration

Respiration is a process in which living things take in oxygen so as to break down digested food to produce energy.

We need energy to live. Our body needs energy to perform its necessary functions such as the beating of our heart. We also need energy to move around and do things.

Although all this energy comes from the food we eat, our body cannot directly make use of it. Energy to live comes from the releasing of energy when food materials and oxygen go through chemical changes so that energy is released from the digested foods.

The process of respiration

For respiration to take place, there has to be a way for oxygen to enter the organism and for carbon dioxide to leave.

The parts of a living thing that enable the exchange of gases with the surroundings is known as the respiratory system.

Breathing

Breathing refers to the exchange of gases with the surroundings, i.e. the taking in of oxygen and the giving out of carbon dioxide and water vapour.

Before respiration can take place, breathing is necessary so that the oxygen used to break down the food can enter the organism. Breathing is also necessary to remove the carbon dioxide and water vapour created during respiration.

Respiration and breathing are often confused with each other.

Both breathing and respiration are required for all living things on earth. However, there is a difference between them. It is important that you are clear about the two terms.

Carbon dioxide and water vapour are given out as waste products.

food

oxygen

undergo chemical changes

Food that we eat gets broken down into simpler substances which are then absorbed into our bloodstream to reach the body cells. That is the process of digestion.

The digested food has to combine with oxygen to be broken down to produce energy.

useful energy


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Respiration refers to the process by which oxygen helps to break down food into useful energy and gives out carbon dioxide as a waste product. Respiration takes place in all living cells. It cannot be consciously controlled.

Breathing is done constantly as living things breathe in and out throughout the day, taking in oxygen and giving out carbon dioxide. It can be consciously controlled.

Different Ways Of BreathingFish, tadpoles and prawns breathe through their gills. These animals live in water, so dissolved oxygen in the water is absorbed into their blood vessels by the gills and carbon dioxide is removed in the same manner.

Worms, toads and frogs breathe through their moist skin.

Insects have small holes called spiracles in their thorax or abdomen. Each spiracle leads to a long tube. The oxygen travels through the tubes directly to the cells in an insect’s body.

Mammals (including humans), birds and reptiles breathe through their lungs.

In humans, the respiratory system enables us to take in oxygen and give out carbon dioxide and water vapour.

The air that is breathed in contains a higher percentage of oxygen and a lower percentage of carbon dioxide and water vapour than the air that is breathed out.

Let’s find out if exhaled air contains carbon dioxide.

Limewater can be used to test for the presence of carbon dioxide.

Take a glass and fill it up with some limewater. Place a straw inside it. Then take a deep breath and blow gently into the straw. The limewater turns milky. This goes to show that the carbon dioxide present in the exhaled air turns the limewater chalky.

Experiment to show that exhaled air contains carbon dioxide

The limewater turns from clear and colourless to chalky.

Air is blown into the limewater through the straw.


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Let’s find out if exhaled air contains water vapour.

When you place a mirror in front of your mouth and exhale into it, you will notice that water droplets can be seen on the mirror surface. This is because water vapour is given out during exhalation (breathing out). Upon coming into contact with the cool surface of the mirror, the water vapour condenses into tiny water droplets.

The Human Respiratory SystemNose

You inhale (breathe in) fresh air about twenty times every minute. The air is drawn into the lungs through your nasal passages.There are tiny hairs and moisture (known as mucus) in the nose which clean the air by filtering out dirt and dust particles.

Windpipe

The air travels down the windpipe, which is a tube leading to the lungs. The tube branches out into two separate smaller tubes, one to each lung.

Air sacs

Both lungs contain many tiny air sacs. When the air breathed in reaches the air sacs, oxygen is taken in and transported to the heart where it will be sent via the bloodstream to all parts of the body.At the same time, the air sacs absorb carbon dioxide produced by the body to be breathed out.

Diaphragm

A thin, dome-shaped muscle lies just below the lungs.When we breathe in, the diaphragm moves downwards as the rib cage moves outwards and upwards. This leaves space for your lungs to expand, and air pressure brings more air in. When your diaphragm relaxes, the space gets smaller and air is pushed out.


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Let’s do a model of the human respiratory system.

Using an empty soft drink bottle and other materials, we can make a model of the human respiratory system as shown below.

Model of the human respiratory system

When you blow into the straw, air enters the ‘lungs’ (balloons). They become inflated (bigger) and the rubber sheet ‘diaphragm’ will move downwards slightly.

When you stop blowing, the balloons deflate and the rubber sheet will move upwards to its original position.

The Plant Respiratory System

Plants need to take in oxygen and give out carbon dioxide during respiration too. Respiration takes place all the time in plants.

Photosynthesis only takes place in the presence of light. During photosynthesis, plants take in carbon dioxide and give out oxygen.

There must be a way for plants to exchange gases with the surroundings.

On the underside of leaves, there are many tiny openings called stomata. They help to facilitate the gaseous exchange for photosynthesis and respiration.

Since the stomata are located under the leaf, they are shielded from the sunlight which may cause the water in the plant to evaporate too quickly.

plasticineplastic bottle with base cut off

straw (windpipe)

two balloons (lungs)

rubber sheet secured to the base of the bottle with a rubber band (diaphragm)


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Air And The Respiratory System


Taken from Nail thoSe McQs! PriMary ScieNce UPPer Block 5/6

1. Which of the following is found in air?A. oxygenB. nitrogenC. argonD. carbon dioxideE. krypton

(1) A and D only(2) A, B and D only(3) A, B, C and D only(4) A, B, C, D and E ( )

2. The diagram below shows a cross-section of a leaf.

tiny openings found on the underside of leaf

What are the tiny openings for?A. To allow the exchange of gases with the surroundingsB. To trap sunlight for the leaf to make foodC. To allow water vapour to be released

(1) A only(2) B only(3) A and B only(4) A and C only ( )

3. A group of people stayed in a poorly ventilated room for a few hours. The following graph showsthe changes in the amount of gases in the room.

Type of gases:oxygencarbon dioxidenitrogenwater vapour

Amount of gases (cm3)

Time

EFGH

Which line is most likely to be wrong?(1) E (2) F (3) G (4) H ( )


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4. What is/are the function(s) of the hair in our nostrils?A. To trap dust and other pollutants in the air that we breathe in and prevent them from entering

our lungsB. To prevent germs from entering our lungsC. To take in more oxygen for the lungsD. To warm the air that we breathe in

(1) A only(2) A and B only(3) C and D only(4) A, B and D only ( )

5. Which of the following are necessary for photosynthesis to take place and are also released duringrespiration?A. waterB. oxygenC. glucoseD. carbon dioxideE. sunlight

(1) A and D only(2) C and D only(3) A, D and E only(4) B, C and E only ( )


Answers: 1. 4 2. 4 3. 3 4. 2 5. 1




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1. Which of the following shows the correct movements of the diaphragm and rib cage when a personrespires?

Rib cage Diaphragm

Breathe in Breathe out Breathe in Breathe out

(1) Up and outwards Down and inwards Moves down Moves up

(2) Down and inwards Up and outwards Moves up Moves down

(3) Up and inwards Down and outwards Moves down Moves up

(4) Up and outwards Down and inwards Moves up Moves down( )

Study the set-up below. Then answer questions 2 and 3.

Two candles are placed in different containers that are filled with oxygen.

Oxygen is pumped into

both containers.

Container P Container Q

2. What is the aim of the experiment?(1) To find out which candle flame will go off first(2) To find out if oxygen is needed for burning(3) To find out which container has more oxygen(4) To find out if the amount of oxygen affects the burning time ( )

3. In order to ensure that the test is fair, what variables must remain unchanged?A. The size of the candlesB. The size of the containersC. The type of gas pumped into the containersD. The time taken for the flame to go off

(1) A and C only(2) B and C only(3) A, C and D only(4) A, B, C and D ( )


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Answers: 1. 1 2. 4 3. 1 4. 3 5. 2

4. Study the flow chart shown below carefully.

Photosynthesisproduces

Gas Xneeded for

Burning

Respiration

needed for

What is gas X likely to be?(1) carbon dioxide(2) nitrogen(3) oxygen(4) hydrogen ( )

5. Which of the following states the role of the lungs in the respiratory system correctly?(1) The lungs pump oxygen to all parts of the body.(2) The lungs allow the exchange of gases with the blood in the body.(3) The lungs transport water and minerals to all parts of the body.(4) The lungs trap the dust particles in the air that is breathed in. ( )

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the respiratory system - sap education...respiratory system. breathing breathing refers to the...

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