Diffusion is the net movement of particles from an area of high concentration to an area of low concentration across a concentration gradient.
Diffusion is animals tend to happen across a semi permiable membrane.
In the human body key areas for diffusion are:
- across the avoli in the lungs (oxygen and carbon dioxide)
- across the placents from mother to baby (oxygen and nutrients) and from baby to mother (carbon dioxide and other waste products)
- across the small intestine into the blood stream (nutrients from digestion inc glucose)
The rate of diffusion is increased by adaptations such as:
- thin surface membrane
- large surface area
- large difference in concentration gradient