Computer-generated image video animation of capillaries. Capillaries are the smallest and most numerous of a body's blood vessels that are part of the microcirculation. Their primary function is to exchange materials between the blood and tissue cells. Only 1 cell thick these microvessels connect arterioles and venules, and enable the exchange of water, oxygen, carbon dioxide, and many other nutrient and waste chemical substances between blood and surrounding tissues. Capillaries animation video from VFX company Polymime, all available to download royalty free.