PATHOLOGY

Detailed explanation-1: -Diffusion is the spontaneous movement of gases, without the use of any energy or effort by the body, between the alveoli and the capillaries in the lungs.

Detailed explanation-2: -Alveoli in the lungs, fish gills and the villi in the small intestine are adapted so that they have short diffusion distance, big concentration difference and large surface area. This means that they are adapted to have a rapid rate of diffusion.

Detailed explanation-3: -The rate of gas exchange is affected by: the area available for diffusion • the distance over which diffusion occurs • the concentration gradient across the gas exchange surface • the speed with which molecules diffuse through membranes.