Download The Breathing System

KS4 Biology
The Breathing System
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Contents
The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary
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Basics of breathing
Humans breathe to ensure that oxygen enters the body
and that carbon dioxide leaves the body.
The breathing system
Oxygen (O2)
Carbon Dioxide
(CO2)
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Parts of the body involved
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 2 breathing processes
The body separates the procedure of breathing in and
breathing out.
Breathing in is one
process and is known as…
Breathing out is a separate
process and is known as…
Inhalation
(When we breathe in
we inhale)
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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What if you forget to breathe?
Firstly the breathing system must inhale oxygen and
secondly it must exhale carbon dioxide.
It 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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What it looks like inside
Well, let us start where air enters the system…
Air enters through either the mouth or the nostrils.
nostril
mouth
nasal cavity
oral cavity
It does not matter through which opening the air enters
because the oral and nasal cavities are connected.
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The pharynx
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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Contents
The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary
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Cartilage in trachea
Diagram of trachea with cartilage rungs.
You can think of the trachea
as a tube lined with Cshaped supporting 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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A clever design
Well, if a tube were lined with fixed circles of
cartilage, it would have a fixed diameter…
cartilage
trachea
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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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Expansion potential
Therefore, a C-shaped piece of cartilage can change shape.
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The trachea
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…
trachea
ciliated epithelial cells
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Ciliated epithelial cells
The cells that line the wall of the trachea show two
special adaptations.
tiny hairs called cilia
produce a sticky liquid mucus
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
ciliated cells
microbes become stuck
within the mucus
mucus being made by the ciliated cells
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Elevator action
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 out
swallowed
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Contents
The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary
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Bronchi
Eventually the trachea
branches, dividing into two
smaller tubes called the left
and right bronchi.
trachea
bronchi
(The singular of bronchi is
a bronchus.)
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 left hand.
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Lungs and bronchi
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
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left bronchi
left lung
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Diagram of a lung
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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Problems with lung expansion
With air entering and leaving the lungs, they 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.
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Danger of friction
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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The pleural membrane
A fluid is found within this bag, surrounding the lungs.
This fluid lubricates the lining of the lungs and stops
friction being generated.
pleural membrane
lung
fluid
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Branching bronchi
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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The route that the oxygen gas takes
Oxygen will pass…
Down the trachea
Through each
bronchus
Always remember
that the CO2 is
moving in the
opposite direction!
And through all the
bronchioles within
each lung
BUT WHAT
HAPPENS NEXT?
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Contents
The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary
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Inside an alveolus
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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A cross-section of an alveolus
oxygen (O2)
gas passes
through here
This O2 is then
able to dissolve in
a small moist
lining.
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epithelial
lining of the
alveolus
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Keeping the environment right
dissolve
moist lining
O2
O2
O2 O 2
dissolve
This moist lining also stops the alveolus from drying and
cracking. It lubricates the insides of the air bag.
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Label the alveolus
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Diffusion at work
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Oxygen diffusion into red blood cells
After the oxygen dissolves it also diffuses.
O2
O2
O2
O2
D IFF USI ON
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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Blood leaving the lungs
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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Laws of diffusion
The movement of the oxygen
from the blood to the cells also
follows the law of diffusion.
blood coming
from the lungs
high
concentration
It is highly concentrated
within the blood.
Meanwhile the concentration
is low within the cell.
low
concentration
body cell
Therefore the oxygen passes
into the body cells.
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Breathing system summary
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 the components
within our breathing system.
Let’s next look 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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©©Boardworks
2004
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Contents
The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary
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Breathtaking features
The breathing system does not have a fixed shape.
trachea
ribs
rib muscles
right bronchus
diaphragm
Right Lung
Left Lung
It has the ability to move, whilst remaining enclosed within
the protection of the ribcage.
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A mobile ribcage?
This means that the rib cage must also be able to
change position.
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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Take a breath
When you breathe in (inhale), your hands move up and outwards.
When you breathe out (exhale), your hands move down and inwards.
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Inhaling: chest expansion
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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The diaphragm
Your diaphragm is located beneath the lungs, which means
that it separates the thorax from the abdomen.
It is a sheet of muscle that
spans the width of the body.
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.
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inhaling
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Pressure regulation
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
High air pressure outside
Low air pressure inside
Low
Air diffuses into the lungs
Diaphragm flattens
Thorax volume increases
Air pressure drops
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Features of inhalation and exhalation
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
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Inhaling
Exhaling
diaphragm shape
flat
domed
ribs
up and out
down and in
diaphragm muscle
contracted
relaxed
rib muscle
contracted
relaxed
lungs
inflated
deflated
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Click on the “Air Drawn In” buttons
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Click on the “Passage of air” buttons
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Match the function with the body part
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Match the function with the body part
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Word play
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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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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Contents
The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary
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Multiple choice section
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Breathing in or out?
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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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