AS Applied Science Revision

The function of the lungs is to swap gases between the atmosphere and our blood. to do this they need to be:

Be thin and have a larger surface area of gases t odiffuse across.

Have a way of getting air in and out of the lungs.

Alveoli and blood capplilaries provide the large thin surface, while air travels through the trachea and bronchial tubes.

Inspiration - Volume of lungs increases

Diaphram moves downwards

Ribcage moves upwards

Preassure in Lungs decreases

Diaphram muscles contract

External intercostal muscles contract

Expiration - Volume of ungs decreases

Diaphram moves up

Diaphram muscles relax

External intercostal muscles relax

Ribcage moves downwards

Preassuer in lungs decreases

From fick's law we can see how efficient lungs are at gas exchange. Ficks law states:

Rate of Diffusion =Area of diffusion surface x difference in concentration

Thickness of surface over which diffusions takes place

Thin exchange surfaces and short diffusion pathway (the alveolar and capillary epithelial cells are very thin and only one cell thick.)

A large surface area (Large number of alveoli and cappliaries).

A steep concentration gradient (lungs are ventilated by breathing and blood is circulated).