Explain the process of diffusion and give one example of where this occurs in the human body?

There are many different types of diffusion that occur in the body however in general they all are the process of a substance moving from an area of high concentration of that substance to and area of low concentration of that substance across a semi-permeable membrane such as the plasma membrane of cells. An example of where this happens is where Oxygen diffuses out of the blood and into the cells of the body lining the capillaries to provide oxygen for respiration.