respiratory system presentation, also showing the mechanism of breathing

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Learningobjectives
© Boardworks Ltd 20061 of 28
Learning objectives
The structures of the respiratory system and their
functions
The mechanisms of breathing
How gases are exchanged during breathing
The composition of inhaled and exhaled air
The different measurements of lung capacity and
breathing
The effects of exercise on the respiratory system
What is meant by aerobic and anaerobic respiration
The oxygen debt.
What we will learn in this presentation:

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The respiratory system

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The nasal passages and lungs
Air is drawn into the body via the nose or mouth.
There are advantages to breathing through your nose:
Air then travels through the larynx, trachea (windpipe),
bronchi (one bronchus to each lung) and bronchioles to
the alveoli, where oxygen passes into the bloodstream.
the air is warmed so that it is closer to
body temperature
tiny hairs and mucus in the nose filter
the air, preventing larger dust and
pollen particles reaching the alveoli
mucus moistens the air, making it
easier for the alveoli to absorb.

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When you breathe in:
intercostal muscles between
the ribs contract, pulling the
chest walls up and out
the diaphragm muscle
below the lungs contracts and
flattens, increasing the size of
the chest
the lungs increase in size,
so the pressure inside them
falls. This causes air to rush in
through the nose or mouth.
Mechanisms of breathing – inspiration
Diaphragm
contracts and
moves down
Intercostal
muscles pull ribs
up and out

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Mechanisms of breathing – inspiration

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Mechanisms of breathing – expiration
When you breathe out:
Intercostal muscles between
the ribs relax so that the chest
walls move in and down.
The diaphragm muscle below
the lungs relaxes and bulges up,
reducing the size of the chest.
The lungs decrease in size, so
the pressure inside increases
and air is pushed up the trachea
and out through the nose or
mouth.
Diaphragm
relaxes and
bulges up
Ribs move in
and down

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Mechanisms of breathing – expiration

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Gas exchange at the alveoli
The alveoli are bunches
of tiny air sacks inside
the lungs.
Each individual sack is
called an alveolus.
When you breathe in,
they fill with air.
The alveoli are covered in tiny capillaries (blood vessels).
Gases can pass through the thin walls of each alveolus and
capillary, and into the blood stream.
Gases can also pass from the blood stream, into the alveolus.

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Gas exchange at the alveoli

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Composition of inhaled and exhaled air
Gas
Amount in
inhaled air
Amount in
exhaled air
Oxygen
Carbon dioxide
Nitrogen
Water vapour
17%
3%
79%
Large amount
21%
Very small amount
79%
Small amount
Why does mouth-to-mouth resuscitation work?
What are the main differences between
inhaled and exhaled air?

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Measuring breathing
Tidal volume is the amount you breathe
in and out in one normal breath.
Residual volume is the amount of air left in your lungs
after you have breathed out as hard as you can.
Minute volume is the volume of air
you breathe in one minute.
Respiratory rate is how many
breaths you take per minute.
Vital capacity is the maximum volume of air you can
breathe out after breathing in as much as you can.

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Measuring breathing

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Calculating minute volume
Question
If you breathe 14 times in one minute (respiratory rate)
and you breathe 0.5 litres in each breath, what is your
minute volume?
Answer:
Minute volume = 14 × 0.5 litres
= 7.0 litres
Remember:
You can calculate a person’s minute volume by multiplying
the volume of air they breathe in one breath, by their
respiratory (breathing) rate.
Minute volume is the volume of air
you breathe in one minute.

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Breathing during exercise
Muscle cell respiration increases – more
oxygen is used up and levels of CO2 rise.
The brain detects increasing levels of CO2 – a
signal is sent to the lungs to increase breathing.
Breathing rate and the volume of air in
each breath increase. This means that
more gaseous exchange takes place.
The brain also tells the heart to beat
faster so that more blood is pumped
to the lungs for gaseous exchange.
More oxygenated blood gets to the
muscles and more CO2 is removed.

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The effects of exercise on lung structures
The respiratory muscles (the
diaphragm and intercostals) get
stronger, so they can make the
chest cavity larger.
This larger chest cavity means
more air can be inspired, therefore
increasing your vital capacity.
More capillaries form around the alveoli,
so more gaseous exchange can take place.
In the long-term, regular exercise strengthens
the respiratory system.
Gas exchange can now take place more
quickly meaning exercise can be maintained
at a higher intensity for longer.