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The
Breathing System
[ Up ] [ Animal Classification ] [ Food and Feeding ] [ The Digestive System ] [ The Breathing System ] [ The Circulatory System ] [ The Lymphatic System ] [ The Nervous System ] [ The Endocrine System ] [ The Reproductive System ] [ The Skeletal System ]
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on the links below
    
The
Lungs
Mammals
have two large lungs in their thorax.
There
are spongy in texture and each have two lobes.
They
are positioned behind the heart and they are protected by the rib cage.
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The
Air We Breath
A
comparison of inhaled air and exhaled air is shown below:
|
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Inspired
Air / %
|
Expired
Air / %
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Nitrogen
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78.6
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74.9
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Oxygen
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20.9
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15.3
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Carbon
Dioxide
|
0.03
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3.6
|
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Water
Vapour
|
0.5
|
3.2
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The
Passage of Air
 Air
enters a mammal through the nose or mouth. The
air then moves to the trachea, through the glottis (the opening at
the back of the mouth) and into the trachea.
The
trachea is kept open by Rings of Cartilage.
At
the top of the trachea is the voice box or larynx.
The
trachea splits into two bronchi (bronchus) at the base.
When
the bronchi enter the lungs they split repeatedly into bronchioles.
Eventually
each bronchiole ends up at an air sac or alveolus.
It
is at the alveoli that gases are exchanged i.e. oxygen taken in and CO2
given out.
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How
the Alveoli work
 The
alveoli are completely covered in blood vessels (capillaries).
The
walls of the capillaries are extremely thin and the distance between air and
blood is only 0.3μm.
This
means that O2 has no distance to travel to get into the blood.
The
alveoli increase the surface area hugely.
Humans
have 300 million alveoli in both lungs giving a total surface area of 80 m2
(The skin is 2m2).
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The
Breathing Action.
 
Breathing
is controlled by the respiratory centre of the hindbrain.
This
area controls the movement of the diaphragm, a muscular sheet which seals the
thorax.
When
the diaphragm contracts, it pulls the lungs downwards and air is forced into the
trachea, bronchi and bronchioles.
When
the diaphragm relaxes, the air is forced out of the lungs and the cycle repeats
itself.
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Related
links & exercises!
Look
at the links below, not all but a few and then complete the puzzles below!!
How your lungs work
How stuff works - Lungs
How you lungs work
again!
Make a model of how the lungs work
Looking
at your lungs
On-line
Quizzes and Exercises
Heart and Lung quiz
Lung quiz
Test
you knowledge of this page with the Breathing System Crossword!
Click
here to find out about the Circulatory System
[ Up ] [ Animal Classification ] [ Food and Feeding ] [ The Digestive System ] [ The Breathing System ] [ The Circulatory System ] [ The Lymphatic System ] [ The Nervous System ] [ The Endocrine System ] [ The Reproductive System ] [ The Skeletal System ]
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Air
enters a mammal through the nose or mouth.