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Gas Exchange In The Lungs
· The body needs a constant supply of oxygen
for the process of respiration. The gas carbon
dioxide is produced as a waste product.
· The lungs are found in the part of the body
called the thorax and this is separated from
our digestive organs by the diaphragm. The
main job of the breathing system is to carry
gases in and out of the lungs.…read more

Slide 3

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When a person breathes in the rib cage moves
up and out and the diaphragm moves from its
normal dome shape to become flatter. These
movements have the effect of increasing the
volume inside the thorax and therefore
decreasing the pressure. This causes air to
travel into the lungs…read more

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Breathing delivers fresh air into the lung
surfaces and it is here that gas exchange will
take place. Oxygen diffuses into the
bloodstream and carbon dioxide will travel in
the reverse direction. Air contains
approximately 80% nitrogen, 20% oxygen and
0.04% carbon dioxide…read more

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The air that we breathe out will contain the
same amount of nitrogen but only 16% oxygen
and 4% carbon dioxide. There will also be a
small increase in the amount of water vapour
that we exhale. Gas exchange occurs in the
alveoli which are special air sacs…read more

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The alveoli are specially adapted for gas
exchange. They provide a large surface area
which is also moist and this helps diffusion.
The cells of the alveoli are also very thin and
so provides a short diffusion path.
· There is also an excellent blood supply to the
alveoli and this provides a steep
concentration gradient which increases the
efficiency of the whole process…read more

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