Diffusion and gas exchange

What is diffusion

Diffusion is the net movement of a substance from an area of high concentration to an area of low concentration, down a concentration gradient.

What is Fick’s Law

Rate of diffusion is proportional to

surface area x difference in conc/length of diffusion path

How is the alveoli adapted for better gas exchange

-Millions of alveoli so large surface area

-Alveolar wall is one cell thick so short diffusion distance

-Extensive capillary network

-Well ventilated

Why can’t larger animals rely on diffusion for cells to be supplied with oxygen

Have small surface area to volume ratio

So there is less surface area available for exchange relative to the animals volume

So can’t meet metabolic demands

Long diffusion distance

Ficks law