Transcript human ventilation

Biology
The development of internal gas exchange surfaces in larger
organisms to maintain adequate rates of exchange. Mammals
(alveoli, bronchioles, bronchi, trachea, lungs), including the
ventilation system.
To enable efficient gas exchange organisms have to
be ‘adapted’. In this case the walls of the alveoli
are made up of a layer of epithelial cells which are
flattened. The capillaries are also made up from
this way. This allows gases to diffuse through two
membranes only. To keep the alveoli moist water
constantly diffuses through it.
The respiratory system is the
gas exchange organ in
mammals. It contains the
following:
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Alveoli
bronchioles
bronchi
Trachea
lungs
This can be seen on the following diagram:
1)
2)
The
concentration
gradient across
the respiratory
system is
maintained by:
Blood flow on
one side
Air flow on the
other side
This allows oxygen
to diffuse down its
own gradient from
air to blood, while
carbon dioxide can
diffuse down its own
concentration
gradient from blood
to air.
The flow of air into and out of the alveoli is known as
Ventilation, and has two stages:
Inspiration:
Expiration:
How it works-
How it works:
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Diaphragm flattens and
contracts
Intercostal muscles contract
making the ribs come up and out
This increases the volume of the
the thorax which in turn
increases the lung and alveoli
volume
Pressure of air is decreased and
so air flows IN to equalise this.
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Diaphragm relaxes and curves
upwards
Ribs fall as intercostal muscles
relax
This decreases volume of thorax
which in turn decreases lung and
alveoli volume.
This increases the pressure of
air and so air flows OUT to
equalise this.
The following
diagram helps explain
this:
Table to show what happens to the composition of air
when it reaches the alveoli
Component
Atmospheric
Air (%)
Expired
Air (%)
N2 (plus inert gases)
O2
CO2
H2O
78.62
20.85
0.03
0.5
100.0%
74.9
15.3
3.6
6.2
100.0%
The
End!