The human

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13
The human
breathing system
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13 The human breathing system
13.1 Gaseous exchange 13.2 The general plan of
the human breathing system 13.3 The process of
gaseous exchange in the alveoli 13.4 The
mechanism ventilation
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13.1 Gaseous exchange
Gaseous Exchange?
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13.1 Gaseous exchange
Environment
O2
Cell
CO2
Gaseous Exchange
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13.1 Gaseous exchange
Environment
O2
Organism
CO2
Respiratory Surface
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13.1 Gaseous exchange
?Definition
Organism takes in O2 from the surroundings get
rid of CO2. This exchange of gases is called
gaseous exchange.
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13.2 The general plan of the human breathing
system
What is the pathway for air to go into the human
breathing system?
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
Cilia
Ciliated
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13.2 The general plan of the human breathing
system
Cilia
Ciliated
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
Particles
Mucus
Mucus-secreting cell
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13.2 The general plan of the human breathing
system
Particles
Mucus
Mucus-secreting cell
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
Cool
Air
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13.2 The general plan of the human breathing
system
Functions
filters
moistens
warms
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13.2 The general plan of the human breathing
system
Breathing System
Digestive System
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
Epiglottis
Close trachea
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13.2 The general plan of the human breathing
system
Membranes
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
Oesophagus
C-shaped cartilage
Ciliated epithelium
Trachea
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13.2 The general plan of the human breathing
system
From larynx
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
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13.2 The general plan of the human breathing
system
Air In
Air Out
Alveolus is the site for gaseous exchange
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13.2 The general plan of the human breathing
system
Experiment 13.2 To examine the trachea and the
lungs of a pig

• Examine a pigs lungs and trachea obtained from a
  butchers shop.
• Caution
• Clean the lungs before the experiment.
• Wear disposable gloves.

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13.2 The general plan of the human breathing
system
Experiment 13.2 To examine the trachea and the
lungs of a pig
Question 1 What colour are the lungs? Why do
they have such a colour?
Question 2 Press them gently with your fingers.
What do they feel like? Why do they feel like
that?
Answer 1 The lungs are pink because they contain
many capillaries.
Answer 2 It gives a spongy feeling. It is
because the lungs are made up of alveoli which
are filled with air
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13.2 The general plan of the human breathing
system
Experiment 13.2 To examine the trachea and the
lungs of a pig
Question 3 What is the name of the structure
that covers the surface of the lungs? What is its
function?
Answer The outer covering of the lungs is the
pleural membrane which secretes fluid to reduce
friction. This is why the surface of the lungs is
slippery.
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13.2 The general plan of the human breathing
system
Experiment 13.2 To examine the trachea and the
lungs of a pig
Question 4 Squeeze the trachea with your
fingers. What does it feel like? Why does it feel
like that?
Question 5 Attach the trachea to a pump. Make
sure that the joint is air-tight. What happens to
the lungs when air is pumped in and out of the
lungs? Explain your observations.
Answer 4 It has an elastic feeling as the wall
of the trachea is stiffened by C-shaped
cartilages.
Answer 5 The lungs inflate as air is pumped
into them.
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13.3 The process of gaseous exchange in the
alveoli
Gaseous Exchange
Mechanism
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13.3 The process of gaseous exchange in the
alveoli
Alveoli
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13.3 The process of gaseous exchange in the
alveoli
Higher oxygen concentration
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13.3 The process of gaseous exchange in the
alveoli
O2 in inhaled air
Across walls of alveolus and capillaries
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13.3 The process of gaseous exchange in the
alveoli
O2
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13.3 The process of gaseous exchange in the
alveoli
Transported in the plasma
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13.3 The process of gaseous exchange in the
alveoli
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13.3 The process of gaseous exchange in the
alveoli
CO2 in exhaled air
Across walls of alveolus and capillaries
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13.3 The process of gaseous exchange in the
alveoli
Summary
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13.3 The process of gaseous exchange in the
alveoli
Summary
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13.3 The process of gaseous exchange in the
alveoli
What are the adaptations
of Alveoli
for gaseous exchange?
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13.3 The process of gaseous exchange in the
alveoli
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13.3 The process of gaseous exchange in the
alveoli
O2 concentration in
100
0
No net movement of oxygen!
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13.3 The process of gaseous exchange in the
alveoli
O2 concentration in
2
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13.3 The process of gaseous exchange in the
alveoli
O2 concentration in
100
0
Maintain a great
2
concentration gradient
High rate of diffusion
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13.3 The process of gaseous exchange in the
alveoli
One-cell thick
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13.3 The process of gaseous exchange in the
alveoli
Summary
Functions
Features
Alveolar wall is one-cell thick
Short distance for diffusion
Large surface area
Highly folded
Steep concentration gradient
Numerous capillaries
Dissolve gases
The walls are moist
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13.3 The process of gaseous exchange in the
alveoli
Exhaled air
Composition of
Inhaled air
More
Less
Used by the Cells
Oxygen
More
Less
Produced by the Cells
Carbon dioxide
Same
Not used by the Cells
Nitrogen
Variable
Saturated
Evaporation from the respiratory surfaces
Water vapour
Variable
Higher
Warmed by the higher body Temperature
Temperature
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13.3 The process of gaseous exchange in the
alveoli
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13.3 The process of gaseous exchange in the
alveoli
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13.3 The process of gaseous exchange in the
alveoli
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13.3 The process of gaseous exchange in the
alveoli
Pleural fluid
when the pleural membranes rub again each other
during breathing
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13.3 The process of gaseous exchange in the
alveoli
Summary
Nasal cavity
Nostril
Pharynx
Pleural membranes
Larynx
Trachea
Rib
Bronchus
Intercostal muscle
Bronchiole
Alveolus
Diaphragm
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.3 To compare the oxygen content of
inhaled and exhaled air
1. Collect a jar of exhaled air over water. Cover
the jar with a cover plate. 2. Collect a jar of
inhaled (atmospheric) air. Cover the jar with
another cover plate.
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.3 To compare the oxygen content of
inhaled and exhaled air
3. Use a burning spoon to put a burning candle
into the gas jar of exhaled air. Record the time
of burning of the candle inside the gas jar. 4.
Now put a burning candle into the gas jar of
inhaled air. Record the time of burning of the
candle inside the gas jar.
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.3 To compare the oxygen content of
inhaled and exhaled air
Question 1 In which jar does the candle burn
longer?
Answer 1 The candle burns longer in the jar of
inhaled air.
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.3 To compare the oxygen content of
inhaled and exhaled air
Question 2 Which gas must be present for the
candle to burn longer?
Question 3 What do the results tell you about
the amount of this gas in inhaled and exhaled air?
Answer 2 Only oxygen can support combustion.
Answer 3 Inhaled air contains more oxygen than
exhaled air.
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.3 To compare the oxygen content of
inhaled and exhaled air
Question 4 Does the flame go out immediately
when the burning candle is put into the gas jar
of exhaled air? What does this show?
Answer 4 The flame does not go out immediately,
showing that exhaled air also contains oxygen.
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.4 To compare the carbon dioxide
content of inhaled and exhaled air
1. Set up the apparatus as shown on the right. 2.
Breathe in and out gently through the rubber
tubing. Do not breathe too hard. 3. Keep doing
this until the lime water in one of the boiling
tubes has changed colour.
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.4 To compare the carbon dioxide
content of inhaled and exhaled air
Question 1 In which tube did bubbles appear
when you breathe out? Question 2 In which tube
did bubbles appear when you breathe in? Why?
Answer 1 Tube B. Answer 2 Tube A. The inhaled
air enters tube A before it goes into the lungs.
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.4 To compare the carbon dioxide
content of inhaled and exhaled air
Question 3 What happened to the lime water in
tubes A and B?
Question 4 What do the results tell you about
the amount of carbon dioxide in inhaled air and
exhaled air?
Answer 3 The lime water in tube A remained clear
while that in tube B turned milky.
Answer 4 Carbon dioxide content in exhaled air
is higher than that in inhaled air.
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13.3 The process of gaseous exchange in the
alveoli
Experiment 13.4 To compare the carbon dioxide
content of inhaled and exhaled air
Question 5 What solution can you use instead of
lime water? If this is used, what changes would
you expect in tubes A and B?
Answer Hydrogencarbonate indicator solution can
be used instead of lime water. It changes from
red to yellow when more carbon dioxide dissolves
in it. Thus it remains red in tube A and turns
yellow in tube B.
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13.4 The mechanism of ventilation
Breathing
Mechanism
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13.4 The mechanism of ventilation
Breathing
(Ventilation)
In
Out
Inspiration
Expiration
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13.4 The mechanism of ventilation
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13.4 The mechanism of ventilation
Inspiration
Chest Volume
Before inspiration
outwards
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13.4 The mechanism of ventilation
Inspiration
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13.4 The mechanism of ventilation
Inspiration
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13.4 The mechanism of ventilation
Inspiration
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13.4 The mechanism of ventilation
Inspiration
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13.4 The mechanism of ventilation
Inspiration
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13.4 The mechanism of ventilation
Inspiration
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13.4 The mechanism of ventilation
Inspiration
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13.4 The mechanism of ventilation
Inspiration
Chest Volume After inspiration
outwards
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13.4 The mechanism of ventilation
Difference?
Inspiration
Chest volume increases
Diaphragm becomes flattened
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13.4 The mechanism of ventilation
Inspiration
Chest volume increases
and smaller than atmospheric pressure
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13.4 The mechanism of ventilation
Intercostal muscles diaphragm muscles
Contract
Relax
Move upwards outwards
Move downwards inwards
Rib Cage
Diaphragm
Flattened
Dome-shaped
Chest Volume
Increases
Decreases
Lower than atmosphere
Higher than atmosphere
Air pressure in lungs
Air rush in
Results in
Air rush out
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13.4 The mechanism of ventilation
Breathing

Exercise
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13.4 The mechanism of ventilation
Rate of Breathing
6 breaths
X breaths

20 s
60 s
X

18
breaths / min
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13.4 The mechanism of ventilation
Depth of Breath
Volume of air breathed in
per breath
2500 - 2000
500
cm3

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13.4 The mechanism of ventilation
1
Rate of Breathing
No. of breaths
per minute
2
Depth of Breath
Volume of air breathed in
per breath
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13.4 The mechanism of ventilation
During exercise
At rest
Depth of breath
Rate of breathing
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13.4 The mechanism of ventilation
During exercise
Depth of breath
Rate of breathing
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breathing system
ventilation
1. nasal cavity
2. pharynx
oxygen
carbon dioxide
3. larynx
exercise
4. trachea
5. lungs
expiration
inspiration
bronchi
bronchioles
alveoli
1. diaphragm
2. Ribs and sternum
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