THE RESPIRATORY SYSTEM
Cells need oxygen to carry out
respiration, and also need a system to dispose of the carbon dioxide produced
as a result of this process. The respiratory system provides a means of gaseous
exchange.
Air taken in through the nose and mouth is passed into the trachea,
which branches into two bronchi, each entering a lung.
Inside the lungs, the bronchi branch into bronchioles which
end at thin-walled sacs called alveoli. The alveoli are lined
with capillaries - the thin walls of which allow respiratory gases to diffuse
in and out of the blood.
Breathing is controlled by a muscle called the diaphragm, found
below the rib cage.
The enormous number of alveoli allows gaseous exchange across a large surface
area. Diseases which damage the alveoli (eg. emphysema) reduce
this surface area.
Asthma is a condition in which the diameter of the bronchioles
is decreased (either through muscle spasm, swelling of the lining or collection
of fluid), resulting in difficulty in getting enough air into the lungs.
Pneumonia is an inflammation of the lungs (usually caused through
infection) which results in fluid collecting in the lower parts of the lungs.
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© 2004 Dr Peter Darben