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What Happens in the Lungs?

In this worksheet, students' understanding of what happens in the lungs will be tested.

'What Happens in the Lungs?' 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

From a young age, we are taught to think of our lungs as two balloons, inflating and deflating as we breathe in and out. Our lungs are, in fact, far more complex.
 
 
So how does the air get into the lungs?


As the air travels down the TRACHEA it is forced to branch off into the two lungs through the BRONCHI (bronchi is simply the plural for bronchus, as shown in the diagram below):
 
 

Lungs diagram

 
 
Once the air passes into the lungs through the initial bronchi, it is then met by more branches. The branches then get smaller and smaller until they are the same thickness as a hair! These tiny branches are called BRONCHIOLES; but the story of the lungs does not end here, as at the end of each bronchiole there are tiny air sacs called ALVEOLI (sing. ALVEOLUS). 
 
 
So what happens in the alveoli?


Inside the alveoli, oxygen is absorbed into the blood and carbon dioxide is removed. This exchange of gases is called DIFFUSION
 
The alveoli provide the lungs with a large surface area for diffusion to take place on and the thin, moist walls are the perfect place for it. Each alveolus is also surrounded by lots of tiny blood vessels called capillaries that carry blood to and from the lungs.

 

Alveoli and gas exchange
 
As the blood passes by the surface of the alveoli, waste carbon dioxide diffuses out of the blood and into the alveoli. 
At the same time, oxygen from the alveoli diffuses into the blood supply where it is then carried around the rest of the body by red blood cells.

 

Time to put all that lovely information to the test....

In the answer box below, write the word which completes this sentence:

Select the word which completes this sentence:

 

Air enters the lungs through branches called _________.

trachea

bronchi

bronchioles

twigs

What are found at the end of each bronchiole? 

lungs

the liver

alveoli

kidneys

Which of the following gases is needed in our body and which is a waste gas that needs to be removed? 

 

 Useful gasWaste gas
Oxygen
Carbon Dioxide

The exchange of gases in the alveoli takes place by which process?

respiration

osmosis

diffusion

breathing

Which of the following features apply to alveoli?

 

Tick the answers you agree with.

 

thick, dry walls

thin, moist walls

a good blood supply

a good water supply

a large surface area

a small surface area

Oxygen diffuses through the walls of the alveoli into what type of cells?

muscle cells

red blood cells

white blood cells

nerve cells

The diagram below shows the process of gaseous exchange in an alveolus.  Study it carefully.  Try to work out what's going on.

 

Using this information, in addition to your knowledge about breathing in humans, answer the question below:

 

 

In which one of these blood vessels would you find deoxygenated blood?

pulmonary artery

pulmonary vein

The diagram below shows the process of gaseous exchange in an alveolus. Again, study it carefully.

 

Using the information in the diagram, in addition to your knowledge about breathing in humans, answer the question below:

 

 

 

In which one of these blood vessels would you find oxygenated blood?

pulmonary artery

pulmonary vein

Once again, the diagram below shows the process of gaseous exchange in an alveolus.

 

Using the information provided here, in addition to your knowledge about breathing in humans, answer the question below. 

 

 

 

Match up the correct part/process below with its function/description.

 

If you can't read the entire description, hover your mouse over the box.

Column A

Column B

capillary
carries oxygenated blood
ventilation
a gas used in respiration
epithelium
supply of air to the lungs
pulmonary artery
carries oxygen
pulmonary vein
brings blood to alveolus
red blood cell
waste gas
diffusion
allows effective diffusion
carbon dioxide
how gas exchange takes place
oxygen
carries deoxygenated blood
film of moisture
lining of alveolus
  • Question 1

In the answer box below, write the word which completes this sentence:

CORRECT ANSWER
EDDIE SAYS
The trachea is the windipe, which air travels down to get to the lungs.
  • Question 2

Select the word which completes this sentence:

 

Air enters the lungs through branches called _________.

CORRECT ANSWER
bronchi
EDDIE SAYS
The bronchi are the major air passages which divert air from the trachea into the lungs.
  • Question 3

What are found at the end of each bronchiole? 

CORRECT ANSWER
alveoli
EDDIE SAYS
Alveoli are the tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place.
  • Question 4

Which of the following gases is needed in our body and which is a waste gas that needs to be removed? 

 

CORRECT ANSWER
 Useful gasWaste gas
Oxygen
Carbon Dioxide
EDDIE SAYS
Carbon dioxide is a waste gas from our respiration and so is not needed in our body and is therefore expelled when we breathe out. We need oxygen for respiration and so the CO2 is exchanged for oxygen in our blood.
  • Question 5

The exchange of gases in the alveoli takes place by which process?

CORRECT ANSWER
diffusion
EDDIE SAYS
The process used in the exchange of gases (oxygen and carbon dioxide) in the alveoli is 'diffusion'.
This means the movement of molecules from where they are at a high concentration (i.e. oxygen in the alveoli) to a lower concentration (i.e. oxygen in the blood).
  • Question 6

Which of the following features apply to alveoli?

 

Tick the answers you agree with.

 

CORRECT ANSWER
thin, moist walls
a good blood supply
a large surface area
EDDIE SAYS
The alveoli have thin, moist walls so that diffusion occurs readily across that surface.. They provide the lungs with a large surface area for diffusion to take place, and they are surrounded by lots of tiny blood vessels which carry blood to and from the lungs.
  • Question 7

Oxygen diffuses through the walls of the alveoli into what type of cells?

CORRECT ANSWER
red blood cells
EDDIE SAYS
Oxygen diffuses through the walls of the alveoli into the red blood cells, which then travel all around the body. The red blood cells have a molecule called HAEMOGLOBIN in them to which the oxygen molecules attach to be carried off around the body.
  • Question 8

The diagram below shows the process of gaseous exchange in an alveolus.  Study it carefully.  Try to work out what's going on.

 

Using this information, in addition to your knowledge about breathing in humans, answer the question below:

 

 

In which one of these blood vessels would you find deoxygenated blood?

CORRECT ANSWER
pulmonary artery
EDDIE SAYS
This can be confusing, as arteries usually carry oxygenated blood. However, the pulmonary artery (from the heart) will bring deoxygenated blood to the lungs to get more oxygen before sending it around the rest of the body. Think of it as the heart receiving deoygenated blood from all over the body and sending it to the lungs for oxygen. What are blood vessels coming from the heart called? Arteries!
  • Question 9

The diagram below shows the process of gaseous exchange in an alveolus. Again, study it carefully.

 

Using the information in the diagram, in addition to your knowledge about breathing in humans, answer the question below:

 

 

 

In which one of these blood vessels would you find oxygenated blood?

CORRECT ANSWER
pulmonary vein
EDDIE SAYS
Now, maybe you're beginning to get this: the pulmonary artery carries deoxygenated blood from the heart to the lungs where the blood can pick up oxygen. Now, the pulmonary vein takes that freshly oxygenated blood back to the heart to be sent all around the body. What do we called blood vessels bringing blood towards the heart? VEINS!
  • Question 10

Once again, the diagram below shows the process of gaseous exchange in an alveolus.

 

Using the information provided here, in addition to your knowledge about breathing in humans, answer the question below. 

 

 

 

Match up the correct part/process below with its function/description.

 

If you can't read the entire description, hover your mouse over the box.

CORRECT ANSWER

Column A

Column B

capillary
brings blood to alveolus
ventilation
supply of air to the lungs
epithelium
lining of alveolus
pulmonary artery
carries deoxygenated blood
pulmonary vein
carries oxygenated blood
red blood cell
carries oxygen
diffusion
how gas exchange takes place
carbon dioxide
waste gas
oxygen
a gas used in respiration
film of moisture
allows effective diffusion
EDDIE SAYS
That's a lot to do and well done if you got them all correct! As usual, with this sort of question, nail the more obvious ones first, like CO2 and oxygen. Some, like 'ventilation', are clear from the diagram above, so use them. Others you may have to infer: the lining tissue that is used all over the body is EPITHELIUM (if you've looked at your cheek cells, you're looking at epithelial cells) and they have to stay moist as diffusion won't work unless it's through water (or, better, an aqueous medium!).
---- OR ----

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