Download breathing systems

Key Stage 4
The Breathing
System
© Boardworks Ltd 2003
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© Boardworks Ltd 2003
Humans breathe to ensure that oxygen enters the body
and that carbon dioxide leaves the body.
Oxygen (O2)
Carbon Dioxide
(CO2)
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The breathing system
Let us now look at the structure of the breathing
system.
The human body can be divided into three regions.
HEAD
THORAX
ABDOMEN
The breathing system is found in the thorax.
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The body separates the process of breathing in and
breathing out.
Breathing in is one process and is known as…
Inhalation
(When we breathe in we inhale)
Breathing out is another separate process and is known as…
Exhalation
(When we breathe out we exhale)
By separating these two processes, the body can concentrate on
the two tasks in turn.
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Firstly it must inhale oxygen
and secondly it must exhale
carbon dioxide
The breathing system is designed to be able to
perform both tasks using the same organs.
One final important fact to remember is that breathing can be
performed without humans having to think about it.
Just imagine that as well as everything else you have to think
about, you would have to remember to tell your body to inhale,
then exhale, then inhale, exhale, inhale, … etc.
There would be no time for anything else.
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So, what does this system look like?
Well, let us start where air enters the system…
Air enters through either the mouth or the nostrils.
Nostril
Nasal cavity
Mouth
Oral Cavity
It does not matter through which opening the air enters because
the oral and nasal cavities are connected.
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As the air passes through the nasal cavity, the air is
smelt, warmed, filtered and moistened slightly.
The air meets at the Pharynx, a junction at back of the
oral cavity.
The Pharynx is a
junction between two
tubes. The air must
travel down only one
of these tubes. One
is the Windpipe
(Trachea) and the
other is the Gullet
(Oesophagus)
Trachea
Gullet
As the name suggests, air must pass down through
the windpipe (trachea).
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You can
think of the
trachea as a
tube lined
with Cshaped
supporting
rungs.
Diagram of trachea with cartilage rungs.
These rings are
made of a tough
material called
Cartilage. They
help to hold the
tube open.
You may be wondering why they are C-shaped and not
full circles.
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Well, if a tube were lined with fixed circles of
cartilage, it would have a fixed diameter…
Cartilage
Trachea
Although this would stop
the tube from
collapsing, this would
also mean that the tube
would not be able to
expand. When we
breathe in, the trachea
must expand to allow
more air in.
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Therefore, a C-shaped piece of cartilage can
change shape.
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As well as being adapted on its outer surface, the trachea
shows adaptations on its inner lining.
If we look closely at the inner surface of the trachea…
ciliated epithelial cells
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The cells that line the wall of the trachea
show two special adaptations.
produce a sticky
liquid called
mucus
tiny hairs called Cilia
Ciliated epithelial cells
We say the cells show specialisation. These
specialised cells have a particular job to do.
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The presence of mucus and cilia on the lining of
the trachea ensures that the air we breathe is
clean and free from disease.
Microbes
travelling down
the trachea
within inhaled
air.
Microbes become
stuck within the
mucus.
Ciliated
Cells
Mucus being made by
the ciliated cells.
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Once the microbes are
stuck in the mucus, the
cilia move the mucus
upwards using a
wafting action. The
mucus passes up to the
top of the trachea
where it can either be
swallowed or coughed
out of the body.
Coughed
Swallowed
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Eventually the
trachea branches,
dividing into two
smaller tubes called
the left and right
Bronchi.
(The singular of
bronchi is a
bronchus)
Trachea
Right
Left
Don’t forget that in a picture of the human body, right becomes
left and left becomes right. Check by holding up your right
hand in a mirror. The person staring back at you will be holding
up their right hand.
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Each Bronchus connects the trachea to a large air sac
known as a Lung. You have two bronchi and therefore your body
has two lungs, a left and a right.
Trachea
Right Bronchi
Right Lung
Left Bronchi
Left Lung
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In reality, the lungs are different in shape.
Here is a more accurate diagram.
Right
Lung
Trachea
Cartilage
Right
Bronchus
Pleural
Membrane
Location of the
heart
Bronchiole
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With air entering and leaving the lungs, they are going
to increase and decrease in size on a regular basis.
When organs in the body increase in size, they will touch other
organs because of the lack of space.
This is a danger because living tissue is very delicate and when
tissues rub against each other, friction could be generated.
Organ 1
Organ 2
FRICTION
This friction could damage the
tissue and kill cells. Therefore, a
protective bag called the Pleural
membrane surrounds the lungs,
which are likely to rub against
other organs during the breathing
process.
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A fluid is found within this bag, surrounding the lungs.
This fluid lubricates the lining of the lungs and stops
friction being generated.
Plural
Membrane
Lung
Fluid
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Each Bronchus now starts branching
to produce smaller and smaller tubes.
Bronchi
These smaller
branches are known as
bronchioles
One bronchus gives rise to many bronchioles. The overall effect is
similar to the branching of a tree from a central trunk.
This branching of the bronchi occurs within both lungs.
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Oxygen will pass
Down the trachea
Through each
bronchus
And through all the
bronchioles within
each lung
Always
remember
that the CO2
is moving in
the opposite
direction!
BUT WHAT
HAPPENS NEXT?
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Oxygen makes its way to special air sacs.
Actually, each air sac
is found to be a
bundle of air sacs.
Together, they are
known as an
Alveolus.
The outside of the
alveolus is covered with
tiny blood vessels.
We can look inside the alveolus to get some
idea of why they are shaped the way they are.
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Here is a cross section:
Oxygen (O2)
gas passes
through here
Lining of
the alveolus
This O2 is then
able to dissolve in
a small moist
lining
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The O2 gas
molecules
O2
O2
O2 O2
dissolve
dissolve
Moist lining
This moist lining also stops the alveolus from drying and
cracking. It lubricates the insides of the air bag.
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After the oxygen dissolves it also diffuses.
O2
O2
O2
O2
DIFFUSION
Cell lining
of alveolus
Cell lining
of
capillary
Blood
The Oxygen molecules must diffuse through both the
lining of the alveolus and the lining of the blood capillary.
They are eventually picked up by red blood
cells.
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The blood now carries this
oxygen to the cells of the body.
Right
Lung
Left
Lung
Blood
vessel
O2
Body cells
O2
Blood
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The movement of the oxygen from the blood to the cells also
follows the law of diffusion.
Blood
coming from
the lungs
It is highly
concentrated
within the blood
High
concentration
Meanwhile the
concentration is
low within the cell
Low
concentration
Body cell
Therefore the Oxygen passes
into the body cells
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Remember that the process of inhalation brings O2
into the body whilst exhalation removes CO2.
So, how does our breathing system
enable us to do this.
Well, inhaling and exhaling are brought
about by certain changes in the
position of our breathing system.
Let us look again at the general structure of this system.
Remember, the breathing system is
found in the upper region of the
body. This is known as the thorax.
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Picture of the
respiratory
system
Trachea
Ribs
Rib muscles
Right
Bronchus
Diaphragm
Right Lung
Left Lung
This system does not have a fixed shape. It has the
ability to move, whilst remaining enclosed within the
protection of the ribcage.
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This means that the rib cage must also be able to
change position.
OBSERVATION
Take your hands and place them flat on your
chest just above your hips on each side of
your body. Now breathe in and out very
deeply. Whilst you do this, watch to see what
happens to your hands.
You should notice the following things…..
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When you breathe in (inhale), your hands move up and
outwards.
When you breathe out (exhale), your hands move down and
inwards.
Let’s see why….
Inhaling
When we inhale, our lungs fill with air.
As they fill, they become enlarged.
The ribs must then move upwards and outwards to
make more room in the thorax.
The overall effect of this is that our chest
expands.
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Your diaphragm is also involved in the inhalation process. It’s
location beneath the lungs means that it separates the thorax
from the abdomen.
It is a sheet of muscle that
spans the width of the body.
Just before we inhale, it is found in a
dome shape.
As we inhale, it contracts
and flattens.
The result of this
change in shape is a
change in the volume
of the thorax.
Inhaling
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As the volume of the thorax increases, the internal air
pressure drops. This means that the air pressure outside the
lungs is greater than the air pressure inside the lungs.
High
Low
•Diaphragm
flattens
•High air
pressure outside
•Thorax volume
increases
•Low air pressure
inside
•Air pressure
drops
•Air diffuses into
the lungs
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If these changes occur when we breathe in, the
opposite must happen when we breathe out.
These changes can be summarised in the table
below...
Feature
Inhaling
Exhaling
Diaphragm
shape
Ribs
Flat
Domed
Up and out
Down and in
Diaphragm
muscle
Rib Muscle
Contracted
Relaxed
Contracted
Relaxed
Lungs
Inflated
Deflated
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Click on the ‘Air Drawn in’ buttons to explore the animation.
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Click on the ‘Passage of air’ buttons to explore the animation.
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“A Load of hot air!”
The following activity will help you review your
understanding of the structure of the breathing system.
Instructions:
•There are 20 questions to answer
•The number in brackets tells you how many letters in the
word.
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“A Load of hot air!”
Questions
1 This is the toxic gas that is released when we breathe
out? (6, 7)
2 When these contract and relax they move the rib-cage out
and in? (3, 7)
3 The name for the minute air sacs that are covered with
blood vessels? (7)
4 The area of the body where the lungs are found? (6)
5 A protective structure surrounding the lungs (3, 4)
6 The trachea branches into _________ (7), one going to
each lung.
7 The circulatory system will take oxygen to the _______
(5) of the body.
8 Directly beneath the lungs is a sheet of muscle known as
the ____________ . (9)
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9
10
11
12
13
14
15
16
The cavity through which we breathe and eat. (5)
The human breathing system contains two of these
large spongy air bags. (5)
The other name for the wind-pipe? (7)
The name for the junction between the oesophagus
and the wind-pipe? (7)
This is one of the dead-end sacs at the end of the
bronchioles (8)
The left ________ (8) connects the left lung to the
trachea.
The gas needed by the body to perform respiration? (6)
The diaphragm separates the breathing system from the
__________.(7)
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17 The area that connects the nose to the pharynx. (5, 6)
18 The main purpose of the breathing system is to
generate _________. (6)
19 One of two openings of the breathing system located
above the mouth. (7)
20 The name of the release of energy from food? (11)
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Activity
“Don’t hold your breath!”
Pretending you are air!
List down the answers to questions 19, 17, 13,
12, 11, 10 and 6. Now re-order the words to
represent a trip through the breathing system,
beginning outside the body. You must also try to
fit the bonus word ‘bronchioles’ into your list.
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Activity
Where’s the air going?
Use answers from questions 1, 7, 18, 15 and 20
to fill in the following explanation of the purpose
of breathing oxygen into our bodies.
When we breathe, we are doing so to fuel the process
of ____________ , which is one of the characteristics
of life. __________ is taken in and ________
__________ is removed in the process. The oxygen
eventually leaves the breathing system and enters the
circulatory system. This then transports the gas around
the body to all the body ________ which can generate
__________.
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Activity
Words that mean the same thing.
Answer the following questions. Be careful, the
spelling is essential!
1. What is the name of one tiny air sac?
2. Many tiny air sacs are known as ________?
3. What is the name of one branch of the
trachea?
4. The name for the tubes that branch from the
trachea are known as ___________?
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Activity
The lungs have to move!
When we breathe in, our lungs fill with
air. Identify two ways our breathing
system creates more room in the thorax
for these inflated lungs.
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Wordsearch
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Does size matter?
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Which means what?
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In and out but which way around?
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Activity
The breathing system is designed to carry out certain
functions. If we look at specific features of the system, we
should be able to explain why they look the way they do.
Read each ‘feature’ (in red) statement and each ‘explanation’ (in
blue) statement. Then try to drag the correct feature to the
explanation.
e.g. small flexible
flap, the epiglottis
covers the trachea when we
swallow to stop the food
passing into the lungs
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Match the correct feature to the explanation.
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Match the correct feature to the explanation.
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Multiple choice questions
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1. When we inhale, muscles between the ribs…
A relax causing the ribcage to move upwards.
B contract causing the ribcage to move downwards.
C relax causing the ribcage to move downwards.
D contract causing the ribcage to move upwards.
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2. When we inhale the diaphragm muscles:
A relax and this causes the diaphragm to return to
its domed position.
B contract and this causes the diaphragm to return
to its domed position.
C contract and this causes the diaphragm to flatten.
D relax and this causes the diaphragm to flatten.
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3. When inhaling, the movement of the ribcage
and diaphragm together combine to cause the volume
of the chest cavity to…
A increase.
B decrease.
C return to normal.
D stay the same.
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4. The change in volume when inhaling causes
the pressure inside the lungs to:
A increase.
B decrease.
C return to normal.
D stay the same.
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5. We inhale when…
A the pressure in the lungs is lower than the air
pressure outside the body.
B the pressures are equal.
C the pressures in the lungs is higher than the air
pressure outside the body.
D when the pressure inside the lungs is greater than
that inside the blood.
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6. Which of the following adaptations make the
exchange of gases across the lung surface effective…
A few, large alveoli with a massive surface area, a dry inner
surface and close proximity to an extensive capillary
network.
B many, large alveoli with a massive surface area, a moist
inner surface and close proximity to an extensive capillary
network.
C many, tiny alveoli with a massive surface area, a moist
inner surface and close proximity to an extensive capillary
network.
D few, tiny alveoli with a small surface area, a dry inner
surface and close proximity to an extensive capillary
network.
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