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Lung Structure
Specialised for
maximum gas
exchange. VERY
LARGE SURFACE
AREA
Oxygen diffuses into
the bloodstream and
carbon dioxide will
travel in the reverse
direction.…read more

Slide 3

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Alveoli Structure
Minute air sacs
Large SA:Vol ratio
=speed up rate of exchange, many surfaces for gas
exchange to occur
Very thin membranes
=minimize diffusion pathway, allow materials to cross
rapidly (of both capillary epithelial and alveoli
epithelial)
Partially permeable
=allow selected materials to diffuse easily
Movement of environmental medium
=maintain diffusion gradient (eg. Lung ventilation)
Movement of internal medium
=maintain diffusion gradient (Eg. Blood transport in
capillaries)…read more

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Inhalation
EXTERNAL intercostal muscles
CONTRACT.
DIAPHRAGM lowers and flattens
THORAX volume increases,
pressure decreases (to lower
then atmospheric pressure)
Air enters lungs from atmosphere…read more

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Exhalation
INTERNAL intercostal muscles
CONTRACT
DIAPHRAGM relaxes, returning
to dome shape, and moves up
THORAX volume decreased
and pressure increased
Air is exhaled to atmosphere…read more

Slide 6

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Pulmonary Ventilation
The total volume of air moved into the
lungs during in one minute.
Pulmonary ventilation (dm3min-1) =
tidal vol (dm3) x ventilation rate (min-1)
Normal Pulmonary
Ventilation rate = 6 dm3
/min
**dm3 is the same as L
(litres)**…read more

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