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of rib cage
and the diaphragm relaxes and assumes its dome shape. These changes
during
increase the pressure on the lungs; their elastic tissue contracts and squeezes
inhalation,
exhalation the air out through the nose to the external atmosphere. This is expiration
(exhalation).
30 X Class Respiration - The energy releasing system
Do you know?
Our lungs are spongy in nature. They are not of the same size. The lung towards left
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is slightly smaller making space for your heart! Lungs are protected by two membranes
called pleura. A fluid filled between these membranes protects the lungs from injury
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and also aid in the expansion of the spongy and elastic lung muscle, as they slide one
over the other.
You must have noticed that your own breathing is slow and shallow
when you are at rest. It is deeper and faster when you exercise hard. Indeed,
patterns of breathing show a great range, for they are coordinated with
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moment-by-moment needs of the body for supply of oxygen and removal
of carbon dioxide.
What other situations affect your breathing?
It has been found that all movements of breathing stop at once when
the nerves leading from the brain to the respiratory muscles are cut.
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What can be concluded from this?
What happens during the process of breathing?
Which gas needs to be removed from our body during exhalation?
Where does the extra amount of gas come from?
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What is the composition of inhaled air?
When exhaled air is compared with inhaled air, is there any differ-
ence in composition?
Gaseous Exchange (alveoli to capillaries)
Gaseous exchange takes place within the lungs by diffusion from the
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alveoli to blood capillaries and vice versa. The carbondioxide in the blood
is exchanged for oxygen in the alveoli. These tiny air sacs in the lungs are
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numerous and only one cell thick. They are surrounded by capillaries that
are also only one cell thick. Blood, dark
red in colour flows from the heart
bronchiole
through these capillaries and collects
oxygen from the alveoli. At the same Alveolar cavity
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carbondioxide
time, carbondioxide passes out of the
capillaries and into the alveoli. When oxygen red blood corpuscles
blood capillary
we breathe out, we get rid of this
carbondioxide. The bright red, oxygen-
rich blood is returned to the heart and
fig-8: Diagram of Alveolus with pulmonary
pumped out to all parts of the body.
capillary
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As a result of gaseous exchange, the composition of inhaled and
exhaled air is different. See the table given below. Approximate values are
given in the table
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Gas % in inhaled air % in exhaled air
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Oxygen 21 16
Carbondioxide 0.03 4.4
Nitrogen 78 78