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The Respiratory System

In this worksheet, students will learn about the respiratory system that allows cells in our body to utilise oxygen breathed in and perform respiration, a chemical reaction that releases the energy needed for our body to perform necessary functions.

'The Respiratory System' worksheet

Key stage:  KS 3

Curriculum topic:   Biology: Structure and Function of Living Organisms

Curriculum subtopic:   Gas Exchange Systems (Breathing)

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

The respiratory system is made up of organs that enable us to use oxygen from the air we breathe in and remove carbon dioxide, which is poisonous to us. The oxygen is used in a chemical reaction that takes place in all cells called respiration.

 

For respiration, the respiratory system and the digestive system work together as the oxygen (from the lungs) reacts with the glucose provided by food we eat. The products of respiration are water and carbon dioxide and we remove them from our body when we exhale.

 

Take care not to confuse breathing in and out with respiration: breathing is only part of respiration (the part where we exchange gases).

 

The diagram shows the respiratory system in humans.

 

Lungs and respiratory system

 

The nose (and nasal cavity) form the first port of entrance of air into our body. The mouth can be used as a secondary entrance when needed.

 

The nose and mouth are connected to the trachea (windpipe).  The trachea allows air to pass through to the lungs. It is covered by the epithelium, made of cells that produce mucus, which traps germs, dirt and dust to prevent it going to the lungs.

 

Towards its end the trachea splits into two branches, the left and the right bronchus (pl. bronchi).  Each bronchus leads to a lung. The bronchi keep separating into branches, which in turn separate into smaller branches: these are the bronchioles that spread throughout the lungs.  Each bronchiole ends in a tiny air sac called an alveolus (pl. alveoli). The lungs are spongy structures, made of many capillaries and millions of tiny air sacs: the alveoli. 

 

Gas exchange

 

Getting oxygen from the air into the blood and removing carbon dioxide is referred to as gas exchange (basically, swapping CO2 for oxygen). The alveoli have several adaptations that allow gas exchange to take place with the maximum effect:

 

1. They provide a large surface area where gas exchange can take place.

2. Their walls are moist and very thin (one cell thick).

3. They have a lot of tiny blood capillaries passing through them.

 

The diagram shows the structure of the alveoli.

 

 

Blood cells pass through the tiny capillaries around the alveoli. The concentration of oxygen in the blood at that point is much lower than in the alveoli, as we have just inhaled.

 

The mechanism of diffusion allows substances to move from an area of a higher concentration to an area of a lower concentration, therefore oxygen passes through the walls of the alveoli into the bloodstream, which takes it to every single cell in the body. At the same time, carbon dioxide brought to the lungs from the rest of the body diffuses into the alveoli so it can be exhaled.

 

Effects of exercise, asthma and smoking

 

When we exercise, our cells need more energy, so more oxygen is taken in to allow a higher rate of respiration. Hard exercise can cause lack of oxygen in the cells. Then the body can go into anaerobic respiration, which allows a limited amount of energy to be released from our food.

 

Things like pollen, hair and dust can cause an asthma attack, which means the bronchioles get inflamed and they swell. The airways narrow, which makes it difficult for air to pass through as we breathe. People who suffer from asthma have to use an inhaler, which relaxes the airways and makes breathing easier.

 

Smoking causes more mucus to be produced by the lining of the trachea and other surfaces in the lungs and this leads to smoker's cough. One result of this can be chronic bronchitis. Mucus production further increases and the lining of the bronchioles thickens. Eventually, this can lead to emphysema and lung cancer.

What is the name of the chemical reaction that takes place in all cells in our body and uses oxygen and glucose to release energy?

 

Write one word.

What are the two chemicals that are the reactants for the process you named in Q1?

carbon dioxide

oxygen

nitrogen

water

glucose

The air you are breathing in right now has to pass through a sequence of passages and so on in order to have a chance of adding oxygen to your blood.

 

Place the following organs and tubes in the correct order (1-5), imagining that you are an oxygen molecule about to enter your body from the air, and eventually ending up in the bloodstream.

 Nose/MouthAlveoliBronchiTracheaBronchioles
1
2
3
4
5

The epithelial cells of the lung surface allow gas exchange and trap germs, dirt and dust in order to prevent them entering the lungs.

 

These cells form a single layer of similar cells. What word is used for this sort of structure, made of similar cells?

Complete this sentence.

 

The lungs are made of millions of tiny air sacs called ________.

bronchioles

alveolus

alveoli

Pick the correct alveoli adaptation for gas exchange.

The alveoli have very thick walls to prevent excess carbon dioxide entering the lungs.

The alveoli provide a dry surface for oxygen to pass through easily.

The alveoli have many blood capillaries around them.

What is the process that allows gas exchange through the walls of the alveoli?

active transport

osmosis

diffusion

During an asthma attack, what happens to the air passages (like bronchi and bronchioles) that make it more difficult to breathe?

they become inflamed

they close up completely

they start bleeding

Smoking can have all sorts of terrible effects upon the body and can lead to a variety of diseases.

 

Which of the following diseases can be directly casued by smoking?

 

Tick all you agree with.

lung cancer

bowel cancer

bronchitis

emphysema

flu

cholera

Right, you've got to do a bit of estimation here.  Those tiny air sacs that form the area of the lungs where gas exchange takes place - how big do you think it is?

 

If it was possible to take out each one of those air sacs and spread them out flat, what area do you think they'd cover (that's the internal area of your lungs for exchanging gases)?  Remember, you don't KNOW the answer - this is estimation.

area of a dinner plate

area of a 40" TV screen

area of a trampoline

area of a tennis court

  • Question 1

What is the name of the chemical reaction that takes place in all cells in our body and uses oxygen and glucose to release energy?

 

Write one word.

CORRECT ANSWER
respiration
EDDIE SAYS
Respiration (not to be confused with the process of breathing) is the process which releases the energy in our food. Later on in your course you will study it in some detail, so it's important to understand the basics now. In your cells, every moment of every day, glucose and oxygen are being combined to release the chemical energy store in the glucose so you can do whatever you want with it. The remains (waste CO2 and so on) are removed.
  • Question 2

What are the two chemicals that are the reactants for the process you named in Q1?

CORRECT ANSWER
oxygen
glucose
EDDIE SAYS
For respiration to take place, both oxygen and glucose need to be present: the glucose contains its store of chemical energy and oxygen is needed in the respiration reaction to release that energy. The products of this reaction, amongst others, are CO2 and water.
  • Question 3

The air you are breathing in right now has to pass through a sequence of passages and so on in order to have a chance of adding oxygen to your blood.

 

Place the following organs and tubes in the correct order (1-5), imagining that you are an oxygen molecule about to enter your body from the air, and eventually ending up in the bloodstream.

CORRECT ANSWER
 Nose/MouthAlveoliBronchiTracheaBronchioles
1
2
3
4
5
EDDIE SAYS
So, this oxygen molecule is first breathed into the body through your nose/mouth. It travels down your trachea and enters your lungs through one of your bronchi, that branch off the trachea. Next these branch and branch into smaller and smaller tubes called bronchioles. The bronchioles end at the alveoli, where the actual gas exchange takes place.
  • Question 4

The epithelial cells of the lung surface allow gas exchange and trap germs, dirt and dust in order to prevent them entering the lungs.

 

These cells form a single layer of similar cells. What word is used for this sort of structure, made of similar cells?

CORRECT ANSWER
tissue
EDDIE SAYS
Epithelial cells line pretty much all your body cavities - here it's the lungs but they form your blood vessels, gut wall and so on. If you think back to your work on cells and cell systems, you'll remember that a layer of similar cells is known as tissue and it's tissues that eventually build up to form organs, like a kidney.
  • Question 5

Complete this sentence.

 

The lungs are made of millions of tiny air sacs called ________.

CORRECT ANSWER
alveoli
EDDIE SAYS
The tiny air sacs in our lungs are called alveoli. Alveolus is just one of the many alveoli, so this option is not correct grammatically.
  • Question 6

Pick the correct alveoli adaptation for gas exchange.

CORRECT ANSWER
The alveoli have many blood capillaries around them.
EDDIE SAYS
The alveoli have several adaptations that allow gas exchange to take place with the maximum effect:
1. They provide a large surface area where gas exchange can take place.
2. Their walls are moist and very thin (one cell thick).
3. They have a lot of tiny blood capillaries passing through them.

The last option is correct.
  • Question 7

What is the process that allows gas exchange through the walls of the alveoli?

CORRECT ANSWER
diffusion
EDDIE SAYS
Diffusion is going on throughout your body all the time. It is the key process that moves substances across surfaces, like the tissues of your lungs. It is a process that works by moving from a high concentration of a substance (like oxygen) to a lower concentration. It's a bit like arriving on a crowded station platform - everyone moves until they are evenly distributed.
  • Question 8

During an asthma attack, what happens to the air passages (like bronchi and bronchioles) that make it more difficult to breathe?

CORRECT ANSWER
they become inflamed
EDDIE SAYS
During an asthma attack, the bronchioles react by becoming inflamed (swollen) which means that the air passage itself becomes narrower, so less air can fit down it. Using an inhaler allows the passages to relax, as the chemical in the inhaler contains an anti-histamine, which reduces the inflammation.
  • Question 9

Smoking can have all sorts of terrible effects upon the body and can lead to a variety of diseases.

 

Which of the following diseases can be directly casued by smoking?

 

Tick all you agree with.

CORRECT ANSWER
lung cancer
bronchitis
emphysema
EDDIE SAYS
Although smoking can lead to a number of terrible consequences for your body, certain afflictions can be directly attributed to smoking. Diseases like lung cancer, bronchitis and emphysema (where the lining of the lung passages breaks down) are all caused by smoking. It can also lead to blocking of arteries and loss of limbs. Awful!
  • Question 10

Right, you've got to do a bit of estimation here.  Those tiny air sacs that form the area of the lungs where gas exchange takes place - how big do you think it is?

 

If it was possible to take out each one of those air sacs and spread them out flat, what area do you think they'd cover (that's the internal area of your lungs for exchanging gases)?  Remember, you don't KNOW the answer - this is estimation.

CORRECT ANSWER
area of a tennis court
EDDIE SAYS
Well, believe it or not, you are designed with a tennis court-sized area inside you for swapping CO2 for oxygen! That makes a massive difference to your ability to be really active. It\'s a bit like broadband speed - the faster your speed, the quicker pages download, etc.. Get oxygen into your body faster and you can do more and faster.
---- OR ----

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