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3.1.4 The lungs of a mammal act as an interface with the environment. Lung
function may be affected by pathogens and by factors relating to lifestyle.

Lung function:
You breathe in and air enters the TRACHEA
This trachea then splits into two bronchi (one going into each lung)
Each bronchus…

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Expiration

This is a passive process and so does not require much energy

The internal intercostals muscles contract whilst the external intercostals muscles
relax

The ribs move DOWN and IN and this decreases the volume in the thorax

The diaphragm muscles relax and so moves upwards

The decreased volume in…

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Prevention and control: bcg vaccine makes people immune, better education,
better housing, improved health facilities better nutrition so immune system is not
weakened.

Pulmonary Fibrosis

Formation of scar tissue in the lungs, the result of an infection such as TB or
exposure to substances such as asbestos and dust.

Scar…

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Elastin is elastic it helps the alveoli return to their normal shape after inspiration
and expiration.
Loss of elastin means the alveoli can't recoil to expel air as well, (it remains trapped
in the alveoli).
It also leads to destruction of the alveoli walls, which reduces the surface area of…

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