BIG IDEAS
A breath of
fresh air
Where are the lungs
and what do they do?
The lungs are important to the body in the
process of breathing. Breathing is when oxygen
is taken from the air outside into the blood.
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Air enters the nose or mouth
and passes down the windpipe
(trachea) into the lungs through
tubes called bronchi.
In humans there are two lungs in the chest. The
lungs are protected by the ribs. These are bones
attached to the backbone to form a cage
structure around the lungs. The lungs are the
site of gas exchange with the air outside.
The bronchi branch
into a network of tubes called
bronchioles which end in
air sacs (alveoli).
The oxygen enters the blood
in the air sacs (alveoli) and is
carried by the blood to all
the cells in the body.
What other organ is found in the chest?
What is another name for the windpipe?
You are learning to:
Describe the structure
of the lungs
Explain how the lungs clean
themselves
Interpret patterns in data
trachea
(or windpipe)
bronchus
bronchiole
alveoli
left lung
(parts of the
body are
described from
the person's
point of view)
diaphragm
FIGURE 1: The structure and function
of the lungs. Can you suggest why
the air sacs have very thin walls?
What route does air take when it is breathed
out, starting from the alveoli?
Keeping the lungs clean
The air that we breathe has dust and smoke particles and
microbes (which cause diseases) in it. These substances
enter the air passages. If they are not removed the lungs
can become diseased.
The tubes in the lungs are lined with two types of
special cells:
those that have tiny hair-like extensions, called cilia
those that produce mucus.
The mucus traps the harmful substances and the cilia
sweep it up and out of the lungs into the throat where it is
swallowed.
What is trapped by the mucus?
How is mucus removed from the lungs?
Suggest what problems would be caused if the
mucus became too thick.
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If the alveoli in a human were
laid out, they would cover an
area about the size of a tennis
court (100 m2)!
mucusproducing
cell
harmful
substances
trapped in
mucus are
swept up
and out
of lungs
cilated cell
FIGURE 2: Mucus-producing
and ciliated cells in the
lungs. What would happen
if the cilia stopped working?
… breathing … cilia … diffuse … gas exchange … lungs
air in,
oxygen rich
alveoli in
the lungs
air out,
carbon dioxide
rich
FIGURE 3: Gas exchange in the
body. Why do think the alveoli
have a such a large surface area?
oxygen carried in
red blood cells
carbon dioxide
carried dissolved
in blood
cells in
the body
Getting oxygen into the body
Is there a link between chest size
and the volume of your lungs? Try
to find out.
Ask someone to measure the
distance between your shoulder
blades. Take a large plastic bottle
and fill this with water. Upend
this bottle of water in a tank of
water and feed a tube up into the
bottle. Take a deep breath. Now
breathe into the tube. By doing
this you will displace some of the
water from the bottle into the
tank. Using the measurements on
the side of the bottle, work out
how much water you have
displaced. This is a measure of
your lung capacity.
● Plot a scatter diagram of
shoulder blade measurements
to lung volume.
● Do your results indicate a
relationship?
● Why can't you breathe out all
the air in your lungs?
Air passes into the lungs and into the alveoli.
Once in the alveoli, oxygen diffuses (passes) from the alveoli
into the blood. Red blood cells in the blood carry the
oxygen to all the cells in the body.
All the cells produce carbon dioxide as a waste product and this is carried in the blood from
the cells to the lungs. The carbon dioxide is breathed out.
If there is a lack of oxygen reaching the cells then they can no longer make enough energy.
Suffocation occurs when air does not get into the lungs.
Explain why you breathe faster and deeper when you do exercise.
Give the route taken by oxygen particles when they pass
into the mouth and travel to the cells.
Respiration or breathing?
Make sure you know the
difference between breathing
and respiration.
Breathing is where air is taken into and out of the body. Air is taken into and out of the body by
the action of the ribs and diaphragm. Oxygen is then used by the cells of the body in respiration.
Respiration produces energy to be used by all the cells. The body is adapted to get as much
oxygen to the cells as possible.
Give two ways in which breathing differs from respiration.
Suggest why we are unable to breathe under water without special breathing apparatus.
… mucus … red blood cell … respiration … rib … suffocation
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