What mimics the process of diffusion in a way that is similar to the way that capillaries exchange materials between the blood and tissues in the body?

Within the tissues, arterioles terminate into a network of microscopic capillaries. Substances move in and out of the capillary walls as the blood exchanges materials with the cells. Before leaving the tissues, capillaries unite into venules, which merge to form larger and larger veins that eventually return blood to the heart. Of all the blood vessels, only capillaries have walls thin enough to allow the exchange of materials between cells and the blood. Their extensive branching provides a sufficient surface area to pick up and deliver substances to all cells in the body.