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
Gas exchange between the blood and the atmosphere
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).